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Luca VINCETTI

Professore Ordinario
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2023 - Analysis of geometrical deformation effects in hollow-core Tube-Lattice Fibers [Relazione in Atti di Convegno]
Soli, E.; Melli, F.; Rosa, L.; Vasko, K.; Benabid, F.; Vincetti, L.
abstract

We have developed a numerical FEM approach for hollow-core Tube-Lattice Fibers to calculate losses due to geometrical deformation along the fiber axis and hereby provide scaling laws to gain insight and assist in design.

2023 - Analytical Formulas for Micro-Bending and Surface Scattering Loss Estimation in Tube Lattice Fibers [Articolo su rivista]
Melli, Federico; Rosa, Lorenzo; Vincetti, Luca
abstract

Simple analytical formulas for micro-bending and surface scattering loss in Hollow-Core Tube Lattice Fibers are here proposed and numerically validated. They can also be applied to other Hollow-Core fibers with similar core-cladding interfaces such as Hybrid cladding Kagome-Tubular, Nested Tubes, and Kagome fibers. Scaling laws for both loss mechanisms are also given and discussed.

2023 - Geometrical Deformation Effects on Loss and Modal Content in Hollow-Core Tube-Lattice Fibers [Relazione in Atti di Convegno]
Melli, F.; Soli, E.; Rosa, L.; Vasko, K.; Benabid, F.; Vincetti, L.
abstract

In this work, we numerically investigate the effects of geometrical deformations due to the fabrication process on propagation loss of the fundamental mode (FM) and modal content in Hollow-Core Tube-Lattice Fibres (HC-TLFs). HC-TLFs are gaining more and more ground in applications (high power beam delivery [1], low latency communications [2], gas-optics [3], and quantum optics [4]) requiring low propagation loss, single-mode operation, and high quality and polarization purity of the propagating light. In the last year, thanks to an intense research activity, these requirements have been fulfilled, at least for ideal geometries. Experimental results show there is still a gap between ideal and measured performance, due to non-idealities introduced by the fabrication process, in particular geometry deformations and silica surface roughness.

2023 - Hollow-core fibers with reduced surface roughness and ultralow loss in the short-wavelength range [Articolo su rivista]
Osório, Jonas H; Amrani, Foued; Delahaye, Frédéric; Dhaybi, Ali; Vasko, Kostiantyn; Melli, Federico; Giovanardi, Fabio; Vandembroucq, Damien; Tessier, Gilles; Vincetti, Luca; Debord, Benoît; Gérôme, Frédéric; Benabid, Fetah
abstract

: While optical fibers display excellent performances in the infrared, visible and ultraviolet ranges remain poorly addressed by them. Obtaining better fibers for the short-wavelength range has been restricted, in all fiber optics, by scattering processes. In hollow-core fibers, the scattering loss arises from the core roughness and represents the limiting factor for loss reduction regardless of the cladding confinement power. Here, we report on the reduction of the core surface roughness of hollow-core fibers by modifying their fabrication technique. The effect of the modified process has been quantified and the results showed a root-mean-square surface roughness reduction from 0.40 to 0.15 nm. The improvement in the core surface entailed fibers with ultralow loss at short wavelengths. The results reveal this approach as a promising path for the development of hollow-core fibers with loss that can potentially be orders of magnitude lower than the ones achievable with silica-core counterparts.

2023 - Overview about E-Mobility Conducted Immunity Tests on ESA Communication Lines [Articolo su rivista]
Righi, S.; Dossi, L.; Tacchini, A.; Camarda, A.; Vincetti, L.
abstract

Due to the complexity of the Automotive Electromagnetic Compatibility legislation in force, this article aims to describe a simplified overview of several technical standards relating to conducted immunity tests on electronic sub-assemblies, where communication lines are involved. The discussed automotive standards reported in this article are: ISO 11452-1 and ISO 11452-4 for continuous narrowband electromagnetic fields immunity test, bulk current injection and tubular wave coupler, IEC 61000-4-5 for immunity against surge events, IEC 61000-4-4 for electrical fast transient/burst events immunity, ISO 10605 for electrostatic discharge events immunity, ISO 7637-2 and ISO 7637-3 for transient disturbances events immunity. For each cited standard, disturbance bandwidth evaluation was performed. Practical examples are reported, with analysis and discussion of some of the adoptable disturbance countermeasures applicable on controlled area network communication lines, and possible design advantages and disadvantages with different types of filtering and suppression circuit solutions.

2022 - A microstructured fiber for streptavidin detection [Relazione in Atti di Convegno]
Khozeymeh, F.; Melli, F.; Capodaglio, S.; Corradini, R.; Benabid, F.; Vincetti, L.; Cucinotta, A.
abstract

The properties of the microstructured optical fibers (MOFs) make them a growing photonics sensing platform with a wide range of applications in medicine, biological, and chemical detection. Particularly in the detection of bio/chemical analytes using the MOFs, the main advantage is the integration of the optical transducer and fluidic part in the unique MOF platform. In this work, we report a Kagome-based lattice MOF for the detection of streptavidin molecules. Interaction between the light coupled into the fiber in form of the LP-like modes and analytes attached to the fiber's internal surface will result in the analyte detection. This study shows that the Kagome-based MOFs can be used for protein molecule detection.

2022 - A Novel Approach to β-Decay: PANDORA, a New Experimental Setup for Future in-Plasma Measurements [Articolo su rivista]
Mascali, D.; Santonocito, D.; Amaducci, S.; Ando, L.; Antonuccio, V.; Biri, S.; Bonanno, A.; Bonanno, V.; Briefi, S.; Busso, M.; Celona, L.; Cosentino, L.; Cristallo, S.; Cuffiani, M.; De Angelis, C.; De Angelis, G.; De Salvador, D.; Di Donato, L.; Ducret, J. -E.; Vakili, A. E.; Fantz, U.; Galata, A.; Gallo, C. S.; Gammino, S.; Isernia, T.; Koivisto, H.; Kratz, K. -L.; Kronholm, R.; La Cognata, M.; Leoni, S.; Locatelli, A.; Maggiore, M.; Maimone, F.; Malferrari, L.; Mancini, G.; Maunoury, L.; Mauro, G. S.; Mazzaglia, M.; Mengoni, A.; Miraglia, A.; Mishra, B.; Musumeci, M.; Napoli, D. R.; Naselli, E.; Odorici, F.; Palladino, L.; Palmisano, G.; Pavone, S.; Pennisi, S.; Perego, A.; Pidatella, A.; Racz, R.; Reitano, R.; Rifuggiato, D.; Rinaldi, M.; Russo, A. D.; Russo, F.; Schillaci, G.; Selleri, S.; Simonucci, S.; Sorbello, G.; Sparta, R.; Taioli, S.; Tinschert, K.; Torrisi, G.; Trifiro, A.; Tsikata, S.; Tumino, A.; Vescovi, D.; Vincetti, L.
abstract

Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of β-radionuclides can change significantly as a function of the ionization state. In this paper we describe an innovative approach, based on the use of a compact plasma trap to emulate selected stellar-like conditions. It has been proposed within the PANDORA project (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) with the aim to measure, for the first time in plasma, nuclear β-decay rates of radionuclides involved in nuclear-astrophysics processes. To achieve this task, a compact magnetic plasma trap has been designed to reach the needed plasma densities, temperatures, and charge-states distributions. A multi-diagnostic setup will monitor, on-line, the plasma parameters, which will be correlated with the decay rate of the radionuclides. The latter will be measured through the detection of the γ-rays emitted by the excited daughter nuclei following the β-decay. An array of 14 HPGe detectors placed around the trap will be used to detect the emitted γ-rays. For the first experimental campaign three isotopes,176Lu,134Cs, and94Nb, were selected as possible physics cases. The newly designed plasma trap will also represent a tool of choice to measure the plasma opacities in a broad spectrum of plasma conditions, experimentally poorly known but that have a great impact on the energy transport and spectroscopic observations of many astrophysical objects. Status and perspectives of the project will be highlighted in the paper.

2022 - Hollow-Core Fiber-Based Biosensor: A Platform for Lab-in-Fiber Optical Biosensors for DNA Detection [Articolo su rivista]
Khozeymeh, Foroogh; Melli, Federico; Capodaglio, Sabrina; Corradini, Roberto; Benabid, Fetah; Vincetti, Luca; Cucinotta, Annamaria
abstract

In this paper, a novel platform for lab-in-fiber-based biosensors is studied. Hollow-core tube lattice fibers (HC-TLFs) are proposed as a label-free biosensor for the detection of DNA molecules. The particular light-guiding mechanism makes them a highly sensitive tool. Their transmission spectrum is featured by alternations of high and low transmittance at wavelength regions whose values depend on the thickness of the microstructured web composing the cladding around the hollow core. In order to achieve DNA detection by using these fibers, an internal chemical functionalization process of the fiber has been performed in five steps in order to link specific peptide nucleic acid (PNA) probes, then the functionalized fiber was used for a three-step assay. When a solution containing a particular DNA sequence is made to flow through the HC of the TLF in an 'optofluidic' format, a bio-layer is formed on the cladding surfaces causing a red-shift of the fiber transmission spectrum. By comparing the fiber transmission spectra before and after the flowing it is possible to identify the eventual formation of the layer and, therefore, the presence or not of a particular DNA sequence in the solution.

2022 - Hollow-core fibers with ultralow loss in the ultraviolet range and sub-thermodynamic equilibrium surface-roughness [Relazione in Atti di Convegno]
Osorio, J. H.; Amrani, F.; Delahaye, F.; Dhaybi, A.; Vasko, K.; Tessier, G.; Giovanardi, F.; Vincetti, L.; Debord, B.; Gerome, F.; Benabid, F.
abstract

2022 - Modal Content and Confinement Loss Evolution with Surface Roughness Profile in Hollow-Core Inhibited Coupling Tube Lattice Fibers [Relazione in Atti di Convegno]
Vasko, K.; Melli, F.; Rosa, L.; Vincetti, L.; Benabid, F.
abstract

We investigate with a numerical model the confinement loss of the higher-order modes of hollow-core inhibited coupling tube lattice fibers as influenced by the power spectral distribution of transverse surface roughness in the glass tubes forming the fiber cladding.

2022 - Thermo-optical numerical modal analysis of multicore fibers for high power lasers and amplifiers [Articolo su rivista]
Rosa, Lorenzo; Mckee, Seyyedhossein; Poli, Federica; Cucinotta, Annamaria; Vincetti, Luca
abstract

Lasers for modern industrial and research applications are required to provide a high average beam power and at the same time be reliable, efficient, and compact. Rare-earth doped single-mode fiber lasers are the most promising solution. Large mode area fibers are effectively used to reduce nonlinear effects and scaling up the beam power which is now bounded by thermal effects. A new cutting-edge approach to the issue involves the use of Multi-Core Fibers (MCFs), coherently combining several lower power beams into a higher power one, and thus pushing the threshold of nonlinearities and transverse mode instabilities to higher power. The amplification process involves heat generation in the doped cores due to quantum defect, which propagates radially and creates a temperature gradient across the fiber cross-section. Even though the cores are optically uncoupled, the refractive index gradient due to thermo-optical effects could cause cross-talk and core mode coupling. In this work, we numerically analyze the performances of 9-core MCFs for high power fiber lasers by taking into account the coupling and bending effects due to the heat load generated by the quantum defect between pump and laser radiation. MCFs show very low sensitivity to heat load and bending, with effectively single-mode behaviour up to 15 um core diameter (effective area 181 um2) and down to 35 um pitch.

2022 - Transverse Roughness Effect on Fundamental Mode Confinement Loss and Modal Content of Hollow-Core Inhibited Coupling Tube Lattice Fibers [Relazione in Atti di Convegno]
Melli, F.; Vasko, K.; Rosa, L.; Vincetti, L.; Benabid, F.
abstract

The effects of the transverse surface roughness on fiber loss and modal content in hollow-core inhibited coupling tube lattice fibers is numerically investigated. Relationship between roughness spectrum and loss of core modes is assessed.

2021 - A Capacitance PCB Sensor for Granular Material with Increased Accuracy [Articolo su rivista]
Ferretti Corradi, R.; Melli, F.; Lenzini, S.; Cardile, N.; Vincetti, L.
abstract

Granular materials like cereals and sands are widely present in different industrial fields like food and agricultural industry. Capacitive planar sensors for granular materials suffer from an additional source of uncertainty related with the random distribution of the grains inside the sensitivity volume. In this letter, we propose a capacitive planar sensor with a new electrode geometry for increasing the sensitivity volume, thus improving the accuracy of the measurements. The geometry is optimized through a design based on numerical simulations in order to maximize the sensitivity volume without reducing the dynamics of the capacitance variation. Experimental results obtained by considering two different granular materials show a reduction of the standard deviation due to granularity of 20% with respect to a classical interdigital electrode structure. Finally, it is experimentally shown that the increased accuracy of the proposed geometry can be fruitfully used for contaminant detection in a mixture of granular materials.

2021 - Analysis and Assessment of Tube Thickness Variation Effect in Hollow-Core Inhibited Coupling Tube Lattice Fibers [Relazione in Atti di Convegno]
Melli, F.; Giovanardi, F.; Rosa, L.; Benabid, F.; Vincetti, L.
abstract

Hollow-Core Inhibited Coupling Fibers have been the target of great investigation efforts due to their peculiar properties [1]. These features, in addition to their capability to handle high power levels, make this kind of fibers very attractive for a wide range of applications such as high-power lasing, light-gas interaction, plasma photonics, quantum physics, terahertz systems, and gas- and bio-sensing. The guidance mechanism of Inhibited Coupling (IC) fibers relies on the spatial mismatch between core modes and cladding modes (CLMs). In this way, the coupling between core and CLMs, caused by their spatial overlap, is dramatically reduced [1]. An effective way to strengthen this effect is to deploy hypocycloid core-contour (i.e. negative curvature) fiber designs [2]. A negative curvature core can be simply obtained by fabricating a cladding structure made of a layer of thin isolated glass tubes arranged around the hollow core (Tube Lattice Fibers - TLFs) [3] , [4]. Although TLFs have reached an extremely low transmission loss and are intensely developed [5] , [6] a gap remains between measured transmission and the theoretical minimum given by confinement loss (CL). This difference can be ascribed to geometrical non-idealities of the fiber structure, introduced during the fabrication process, even though a theoretical analysis showing the real reason for this gap is not yet available.

2021 - Analytical Formulas for Dispersion and Effective Area in Hollow-Core Tube Lattice Fibers [Articolo su rivista]
Rosa, Lorenzo; Melli, Federico; Vincetti, Luca
abstract

In this work, we propose analytical formulas for the estimation of dispersion properties and effective area of the fundamental mode of hollow-core inhibited coupling fibers with a microstructured cladding composed by a ring of dielectric tubes. The formulas are based on a model which has already been successfully applied to the estimation of confinement loss. The model takes into account the effects of the coupling of the fundamental core mode with the cladding modes in the context of the single-tube approximation. Effective index, group velocity dispersion, and effective area of the fundamental mode are estimated and compared with the results obtained from numerical simulations, by considering ten different fibers. The comparison shows a good accuracy of the proposed formulas, which do not require any tuning of fitting parameters. On the basis of the analysis carried out, a scaling law relating the effective area to the core radius is also given. Finally, the formulas give a good estimation of the same parameters of other Hollow-core inhibited coupling fibers, such as nested, ice-cream, and kagome fibers.

2021 - Circularly-polarized CTS Array Antenna for SatCom applications [Relazione in Atti di Convegno]
Lenzini, S.; Del Mastro, M.; Vincetti, L.; Ettorre, M.
abstract

This paper proposes a circularly-polarized continuous transverse stub(CTS) array antenna for space applications. The radiating structure consists of open-ended parallel plate waveguides(PPW), supporting the propagation of the transverse electromagnetic(TEM) and first transverse electric(TE1) modes. Such modes are orthogonally-polarized in the PPW cross-section and, if properly excited, can generate circular polarization(CP). The antenna radiating section consists of 32 long slots, parallel-fed by a quasi-optical system through a PPW-based corporate feed network(CFN) and an electric field rotator. The proposed antenna is matched in the 27.5-31GHz band while scanning up to +-20° in elevation, with an axial ratio(AR) below 3dB.

2021 - Design and fabrication of a single-mode and ultra-low loss hollow-core fiber based on Kagome-tubular hybrid lattice [Relazione in Atti di Convegno]
Amrani, F.; Osorio, J. H.; Delahaye, F.; Giovanardi, F.; Vasko, K.; Vincetti, L.; Debord, B.; Gerome, F.; Benabid, F.
abstract

We propose a hybrid Kagome-tubular lattice hollow-core fiber for ultra-low loss and single-mode operation. The fiber displays a minimum loss of 1.6dB/km at 1050nm and a higher-order modes extinction of 47dB for a 10m-long fiber.

2021 - Hybrid inhibited-coupling and photonic bandgap hollow core fiber for telecom wavelength range [Relazione in Atti di Convegno]
Vasko, K.; Debord, B.; Rosa, L.; Vincetti, L.; Benabid, F.
abstract

We numerically demonstrate that a hollow-core fiber with a cladding comprised with a first-ring with non-touching tubes surrounded by a photonic bandgap outer-cladding combines low confinement loss, low optical overlap with silica and single modedness.

2021 - Low-loss single-mode hybrid-lattice hollow-core photonic-crystal fibre [Articolo su rivista]
Amrani, F.; Osorio, J. H.; Delahaye, F.; Giovanardi, F.; Vincetti, L.; Debord, B.; Gerome, F.; Benabid, F.
abstract

Remarkable recent demonstrations of ultra-low-loss inhibited-coupling (IC) hollow-core photonic-crystal fibres (HCPCFs) established them as serious candidates for next-generation long-haul fibre optics systems. A hindrance to this prospect and also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the difficulty in designing and fabricating an IC-guiding fibre that combines ultra-low loss, truly robust single-modeness, and polarisation-maintaining operation. The design solutions proposed to date require a trade-off between low loss and truly single-modeness. Here, we propose a novel IC-HCPCF for achieving low-loss and effective single-mode operation. The fibre is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of a microstructured cladding allows us to significantly reduce the confinement loss and, at the same time, preserve truly robust single-mode operation. Experimental results show an HKT-IC-HCPCF with a minimum loss of 1.6 dB/km at 1050 nm and a higher-order mode extinction ratio as high as 47.0 dB for a 10 m long fibre. The robustness of the fibre single-modeness is tested by moving the fibre and varying the coupling conditions. The design proposed herein opens a new route for the development of HCPCFs that combine robust ultra-low-loss transmission and single-mode beam delivery and provides new insight into IC guidance.

2021 - Millimeter Wave Automotive Antenna for 5G Communications [Relazione in Atti di Convegno]
Lenzini, Stefano; Mazzinghi, Agnese; Cerretelli, Matteo; Vincetti, Luca
abstract

2021 - 3D Automotive Antenna for 5G and V2X communications [Relazione in Atti di Convegno]
Corradi, Riccardo Ferretti; Lenzini, Stefano; Melli, Federico; Notari, Andrea; Vincetti, Luca
abstract

2020 - Hollow-core fibers with specific modal operation and low loss in the short-wavelength range [Relazione in Atti di Convegno]
Osorio, J. H.; Amrani, F.; Delahaye, F.; Giovanardi, F.; Vincetti, L.; Debord, B.; Gerome, F.; Benabid, F.
abstract

We report on inhibited-coupling hollow-core optical fibers exhibiting specific modal operation and low loss in the short-wavelength range. We show that judicious choice of the fiber cladding structure allows obtaining fibers that favor the propagation of higher-order modes and fibers which combine effective single-mode operation and low loss. Moreover, we report on recent improvements in hollow-core fibers with ultralow loss in the visible and ultraviolet range.

2020 - Low cost 3D tin sheet multiband shark-fin antenna for LTE MIMO vehicular application [Articolo su rivista]
Melli, F.; Lenzini, S.; Cerretelli, M.; Coscelli, E.; Notari, A.; Vincetti, L.
abstract

A low cost and low-profile multiband 3D antenna for roof-top vehicular applications is presented. The radiating element is obtained through a folded metal sheet shaping a geometry that makes the antenna works in the LTE (Long-Term Evolution) bands. Thanks to its particular shape and its small size the antenna can be positioned under the automotive common used shark-fin case. Furthermore, the design allows an easy industrialization process, using low cost material. In fact, the designed shape needs only to be cut and folded without any welding process. In addition to the designed antenna, simulations and measurements take into account another radiating element in order to analyze its behavior in a MIMO (Multiple-Input-Multiple-Output) configuration. For the proposed solution good performances have been demonstrated from both numerical and measurements results.

2020 - Non-idealities in hollow core inhibited coupling fibers [Relazione in Atti di Convegno]
Melli, F.; Giovanardi, F.; Rosa, L.; Vincetti, L.
abstract

Hollow Core Inhibited Coupling Fibers are experiencing an impressive reduction of their propagation loss. Despite that, there is still a difference between experimental loss and the theoretical minimum defined by confinement loss. This difference is assumed to be due to additional losses caused by geometrical irregularities of the real fibers compared to the ideal geometry, due to the fabrication process. In this work, we numerically investigate additional losses coming from several kinds of geometrical imperfections, highlighting their impact in defining fiber total loss.

2020 - Thermo-optic effects in multicore fibers for high-power lasers [Relazione in Atti di Convegno]
Rosa, Lorenzo; Mckee, Seyyedhossein; Vincetti, Luca; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria
abstract

Multi-core fibers (MCFs) are promising solutions for high power fiber based devices as they reduce nonlinearity and other unwanted detrimental effects, like transverse mode instability, by transporting, instead of a single high power beam, several low-powered ones to be coherently combined at the fiber output. This method relies on accurate evaluation of the phase differences between signals in different cores, which are significantly impacted by changes in the effective index of the propagating modes. For this to be effective, spatial heat generation must be accounted for. In particular, the heat flux from the doped cores to the external boundary causes a temperature gradient across the fiber, which affects the refractive index distribution, creating the chance for effective index change and thus dephasing of the output beams, which is harmful for beam combining. The results of in-depth numerical analysis on the performance of 9-core and 16-core MCFs under thermal effects are presented by studying the mode phase sensitivity to heat load and by introducing a coupled-mode theory model to study possible optical coupling effects. The effectively single-mode condition is also investigated by calculating the core modal overlap differences between fundamental and higher-order modes.

2019 - A simple analytical model for confinement loss estimation in hollow-core Tube Lattice Fibers [Articolo su rivista]
Vincetti, Luca; Rosa, Lorenzo
abstract

In this work, we propose an analytical model for estimating confinement loss in Tube Lattice Fibers. It is based on the single-tube model and the inhibited coupling waveguiding mechanism. The comparison with numerical simulations of tube lattice fibers having different geometrical parameters and dielectric refractive indexes demonstrates the model validity and effectiveness. Being based only on analytical closed formulas, it constitutes a useful tool for rapid estimation of TLF CL. It also gives a more in-depth insight into the TLF guiding mechanisms, confirming the inhibited coupling is an appropriate and effective model for such kind of fibers.

2019 - Complex permittivity measurements of hydraulic oil at UHF and microwave frequencies [Relazione in Atti di Convegno]
Lenzini, Stefano; Rosa, L.; Vincetti, L.
abstract

The results about the measurements of complex permittivity of hydraulic mineral oil is here presented. Two different oil samples were analyzed using this method: a non-used one and a sample with 1000 hours of usage. The obtained data were collected by using the cavity perturbation technique exploiting a coaxial cavity resonator. To overcame the approximations that are usually made in this technique a particular measurement procedure based on 3D-full wave electromagnetic simulations has been performed.

2019 - Core modal spatial-structuring in inhibited-coupling hollow-core fibers [Relazione in Atti di Convegno]
Osorio, J. H.; Chafer, M.; Debord, B.; Giovanardi, F.; Cordier, M.; Maurel, M.; Delahaye, F.; Amrani, F.; Vincetti, L.; Gerome, F.; Benabid, F.
abstract

A profound knowledge of the cladding mode properties and their interaction with the core modes is decisive for successfully designing inhibited-coupling (IC) guiding hollow-core photonic-crystal fibers (HC-PCFs). In IC fibers, the core and cladding modes coupling is robustly minimized due to a strong mismatch between their transverse phases and a small overlap between their fields. In the latest years, great attention has been given to IC fibers, especially since the introduction of the hypocycloid core contour concept [3], which entailed a dramatic loss reduction and preceded the development of single-ring tubular-lattice (SR-TL) HC-PCFs [4]. The interest on SR-TL HC-PCFs is due to their noteworthy properties such as geometric simplicity and the absence of connecting nodes in the fiber cladding, which favors IC guidance. Efforts on SR-TL HC-PCFs development entailed the accomplishment of ultra-low loss and broad transmission bandwidth [5]. Here, we show that the alteration of the lattice-tubes azimuthal position in SR-TL HC-PCFs causes modifications in the mode loss hierarchy and can be used to select the propagation of specific higher order modes (HOMs). It can be done by conveniently enlarging the spacing between the cladding tubes and by providing additional leakage to the fundamental mode while keeping low impact in the confinement loss (CL) of specific HOMs. It allows obtaining uncommon intensity profiles and polarization properties at the fiber output allowing it to act as a mode shaper.

2019 - Guidance properties and phase shift of a 9-core fiber amplifier for high power operation in presence of consistent thermal load [Relazione in Atti di Convegno]
Molardi, Carlo; Pallangal, Shahul H.; Rosa, Lorenzo; Vincetti, Luca; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria
abstract

Multi-core fiber capability to deliver several independent beams in a single structure has been deeply investigated to obtain spatial multiplexing in optical communication. Recently, the coherent beam multiplexing idea has been extended to high power fiber laser field, where multi-core fiber amplifiers, combining low power beams, promise to overcome thermal mode instability, which characterizes single-core fiber amplifiers. Although coherent output beam combination is advantaged in multi-core fiber, the understanding of core phase shifts is necessary to implement efficient beam combination. In presence of thermal load, induced by pump-to-signal conversion quantum defect, a refractive index gradient is formed on the multi-core fiber amplifier cross-section, thus changing core propagation properties and possibly creating unwanted core couplings. In this work a 9-core double-cladding fiber amplifier is numerically investigated by varying the core thermal load, from 2 to 15 W/m, in order to understand the structure propagation mismatch. The 9 cores are organized in a 3×3 regular grid, each core has a diameter of 19 μm and a spacing of 55 μm. Cores numerical aperture is 0.06. The outer cladding has a diameter of 340 μm. A comparison between a rod-type fiber amplifier configuration and a flexible fiber amplifier has been performed. Results show that the cores can be divided in three groups according to their propagation properties: central core, side cores, and corner ones. The phase shift between these groups, or equivalently the effective index difference, becomes higher with the increase of thermal load. These observations are fundamental to implement a model for beam propagation in presence of thermal effect, to investigate the amplification dynamics along z-direction.

2019 - Guidance properties and thermal effects in 9-core Yb-doped fiber for high power applications [Relazione in Atti di Convegno]
Mckee, S.; Poli, F.; Selleri, S.; Cucinotta, A.; Rosa, L.; Vincetti, L.
abstract

In this abstract, the performance of optically uncoupled cores in 9-core multi core fibers for high-power fiber lasers is evaluated by considering thermal effects due to the heat load originated by quantum defect between pump and laser radiation. For high power applications, thermal effects are currently seen as the main constraint to power scaling of fiber lasers. The finite-element method is employed to model the optical field distribution for optical amplification and lasing, in order to analyze the effect of heat load on the modes of ytterbium-doped multi-core fibers.

2019 - Hollow Core Inhibited Coupling Fibers for Biological Optical Sensing [Articolo su rivista]
Giovanardi, Fabio; Cucinotta, Annamaria; Rozzi, Andrea; Corradini, Roberto; Benabid, Fetah; Rosa, Lorenzo; Vincetti, Luca
abstract

In this work, we report how tube lattice hollow-core fibers can be successfully used to build sensors for molecule detection. The inner silica surface of the fiber is functionalized and coated with a probe layer, which permits to bond only with a particular molecule (the target). When the fiber is infiltrated with a solution containing the target an additional layer is crated on the silica surface causing a redshift of the fiber transmission spectrum. The technique does not require any additional transducer component such as Bragg gratings, amplifying techniques such as nano-particles nor coherent sources. It simply consists of the measurement of the transmission spectrum of a piece of fiber some tens centimeters long. The principle is validated with experimental results showing the detection of streptavidin protein. A solution containing streptavidin was flowed trough the hollow core of the fiber coated with biotine. The measurement of the transmitted spectrum before and after the infiltration showed the presence of a some nanometer thick bio-layer.

2019 - Hollow-Core Fiber Technology: The Rising of “Gas Photonics” [Articolo su rivista]
Debord, Benoît; Amrani, Foued; Vincetti, Luca; Gérôme, Frédéric; Benabid, Fetah
abstract

Since their inception, about 20 years ago, hollow-core photonic crystal fiber and its gas-filled form are now establishing themselves both as a platform in advancing our knowledge on how light is confined and guided in microstructured dielectric optical waveguides, and a remarkable enabler in a large and diverse range of fields. The latter spans from nonlinear and coherent optics, atom optics and laser metrology, quantum information to high optical field physics and plasma physics. Here, we give a historical account of the major seminal works, we review the physics principles underlying the different optical guidance mechanisms that have emerged and how they have been used as design tools to set the current state-of-the-art in the transmission performance of such fibers. In a second part of this review, we give a nonexhaustive, yet representative, list of the different applications where gas-filled hollow-core photonic crystal fiber played a transformative role, and how the achieved results are leading to the emergence of a new field, which could be coined "Gas photonics". We particularly stress on the synergetic interplay between glass, gas, and light in founding this new fiber science and technology.

2019 - Low Profile Wideband 3D Antenna for Roof-Top LTE Vehicular Applications [Relazione in Atti di Convegno]
Melli, Federico; Lenzini, Stefano; Cerretelli, M.; Coscelli, E.; Notari, A.; Selleri, S.; Vincetti, L.
abstract

In this study, a low profile wideband 3D antenna for roof-top LTE vehicular applications is presented. The structure consists of folded metal sheets welded together building a geometry that allows covering two LTE bands: 700MHz-960MHz, 1700MHz-2700MHz. The shape and the size of the antenna allow to fit it under the shark-fin case, and thanks to the chosen material the production costs are low. Simulations and measurements have been performed taking into account two antennas working as a MIMO configuration. Both numerical and measurement results show good performances in terms of return loss, coupling and gain.

2019 - Mid IR hollow core fiber gas laser emitting at 4.6 μm [Articolo su rivista]
Aghbolagh, F. B. A.; Nampoothiri, V.; Debord, B.; Gerome, F.; Vincetti, L.; Benabid, F.; Rudolph, W.
abstract

Emission at 4.6 μm was observed from an N2O filled hollow core fiber laser. 8-ns pump pulses at 1.517 μm excited a vibrational overtone resulting in lasing on an R and P branch fundamental transition from the upper pump state. At optimum gas pressure of 80 Torr, photon conversion efficiency of 9% and slope efficiency of 3% were observed from a mirrorless laser. The laser threshold occurred at absorbed pump energy of 150 nJ in a 45-cm long fiber with 85 μm core diameter. The observed dependence of the laser output on gas pressure was shown to be a result of line broadening and relaxation rates.

2019 - Mid-IR HCPCF gas-laser emitting at 4.6 µm [Relazione in Atti di Convegno]
Gerome, F.; Aghbolagh, F.; Nampoothiri, V.; Debord, B.; Vincetti, L.; Benabid, F.; Rudolph, W.
abstract

Infrared laser sources emitting in the atmospheric transmission window (i.e. the wavelength range of 3-5 µm and 8-13 µm) are of interest in applications such as remote sensing, imaging and free-space communications [1]. Within this context, Inhibited Coupling Hollow Core Photonic Crystal Fibers (IC-HCPCF) [2] offer an interesting platform for gas laser sources, especially for those emitting in spectral ranges where silica-based solid core fiber lasers fail because of the large infrared (IR) absorption losses of the host materials. Indeed, the possibility of filling HCPCF with gases, and combining long gas-light interaction lengths with small modal areas opened new avenues for laser development and nonlinear optics [3]. Furthermore, IC-HCPCFs exhibit particularly weak optical overlap between the guided field and the glass cladding material (typically in the range 10-4-10-6) [4]. Consequently, material absorption losses play a minor role in the mid-IR in a few meter-long silica-based IC-HCPCF as demonstrated previously [5]. This suggests that the concept of hollow fiber gas laser (HOFGLAS), which was demonstrated in the visible with I2 [6] and at 3 µm with C2H2 pulsed [7] and CW [8], can be extended to longer wavelengths. Here, we report on an optically pumped gas-laser based on N2O-filled IC-HCPCF. The pulsed N2O HOFGLAS is pumped at 1.517 µm and emits at 4.6 µm with a photon conversion efficiency of 9% and a slope efficiency of 3%.

2019 - Mid-IR HCPCF gas-laser emitting at 4.6 μm [Relazione in Atti di Convegno]
Gerome, F.; Aghbolagh, F.; Nampoothiri, V.; Debord, B.; Vincetti, L.; Benabid, F.; Rudolph, W.
abstract

Infrared laser sources emitting in the atmospheric transmission window (i.e. the wavelength range of 3-5 µm and 8-13 µm) are of interest in applications such as remote sensing, imaging and free-space communications [1]. Within this context, Inhibited Coupling Hollow Core Photonic Crystal Fibers (IC-HCPCF) [2] offer an interesting platform for gas laser sources, especially for those emitting in spectral ranges where silica-based solid core fiber lasers fail because of the large infrared (IR) absorption losses of the host materials. Indeed, the possibility of filling HCPCF with gases, and combining long gas-light interaction lengths with small modal areas opened new avenues for laser development and nonlinear optics [3]. Furthermore, IC-HCPCFs exhibit particularly weak optical overlap between the guided field and the glass cladding material (typically in the range 10-4-10-6) [4]. Consequently, material absorption losses play a minor role in the mid-IR in a few meter-long silica-based IC-HCPCF as demonstrated previously [5]. This suggests that the concept of hollow fiber gas laser (HOFGLAS), which was demonstrated in the visible with I2 [6] and at 3 µm with C2H2 pulsed [7] and CW [8], can be extended to longer wavelengths. Here, we report on an optically pumped gas-laser based on N2O-filled IC-HCPCF. The pulsed N2O HOFGLAS is pumped at 1.517 µm and emits at 4.6 µm with a photon conversion efficiency of 9% and a slope efficiency of 3%.

2019 - Phasing and guidance properties of multi-core fibers under heat load [Relazione in Atti di Convegno]
Rosa, L.; Mckee, S.; Molardi, C.; Poli, F.; Selleri, S.; Vincetti, L.; Cucinotta, A.
abstract

Multi-core fibers are a technology currently at the forefront of research due to the increasing need for efficient transport of high-power continuous and pulsed laser beams [1], Power scaling is gained by propagating independent beams through spatial multiplexing in different cores to avoid thermal instability issues [2], shifting the traditional trade-off involved in enlarging the mode area while preserving single-mode operation. Phase difference compensation between the various beams is achieved by a piezo mirror system, and experimental results show that onset of multi-modality in heated cores is one of the main causes of efficiency reduction [2].

2019 - Phasing and guidance properties of multi-core fibers under heat load [Relazione in Atti di Convegno]
Rosa, L.; Mckee, S.; Molardi, C.; Poli, F.; Selleri, S.; Vincetti, L.; Cucinotta, A.
abstract

Multi-core fibers are a technology currently at the forefront of research due to the increasing need for efficient transport of high-power continuous and pulsed laser beams [1]. Power scaling is gained by propagating independent beams through spatial multiplexing in different cores to avoid thermal instability issues [2], shifting the traditional trade-off involved in enlarging the mode area while preserving single-mode operation. Phase difference compensation between the various beams is achieved by a piezo mirror system, and experimental results show that onset of multi-modality in heated cores is one of the main causes of efficiency reduction [2].

2019 - Strong nonlinear optical effects in micro-confined atmospheric air [Articolo su rivista]
Debord, B.; Maurel, M.; Gerome, F.; Vincetti, L.; Husakou, A.; Benabid, F.
abstract

Historically, nonlinear optical phenomena such as spectral broadening by harmonic generation have been associated with crystals owing to their strong nonlinear refractive indices, which are in the range of similar to 10(-14) cm(2)/W. This association was also the result of the limited optical power available from early lasers and the limited interaction length that the laser-crystal interaction architecture could offer. Consequently, these limitations disqualified a large number of materials whose nonlinear coefficient is lower than n(2)similar to 10(-16) cm(2)/W as suitable materials for nonlinear optics applications. For example, it is a common practice in most of optical laboratories to consider ambient or atmospheric air as a "nonlinear optically" inert medium due to its very low nonlinear coefficient (similar to 10.10(-1)9 cm(2)/W) and low density. Today, the wide spread of high-power ultra-short pulse lasers on one hand, and low transmission loss and high-power handling of Kagome hollow-core photonic crystal fiber on the other hand, provide the necessary ingredients to excite strong nonlinear optical effects in practically any gas media, regardless of how low its optical nonlinear response is. By using a single table-top 1 mJ ultra-short pulse laser and an air exposed inhibited-coupling guiding hollow-core photonic crystal fiber, we observed generation of supercontinuum and third harmonic generation when the laser pulse duration was set at 600 fs and Raman comb generation when the duration was 300 ps. The supercontinuum spectrum spans over similar to 1000 THz and exhibits a typical spectral-density energy of 150 nJ/nm. The dispersion profile of inhibited-coupling hollow-core fiber imprints a distinctive sequence in the supercontinuum generation, which is triggered by the generation of a cascade of four-wave mixing lines and concluded by solitonic dynamics. The Raman comb spans over 300 THz and exhibits multiple sidebands originating from N-2 vibrational and ro-vibrational Raman transitions. With the growing use of hollow-core photonic crystal fiber in different fields, the results can be applied to mitigate air nonlinear response when it is not desired or to use ambient air as a convenient nonlinear medium. (C) 2019 Chinese Laser Press

2019 - Superradiance from lattice-confined atoms inside hollow core fibre [Articolo su rivista]
Okaba, S.; Yu, D.; Vincetti, L.; Benabid, F.; Katori, H.
abstract

Unravelling superradiance, also known as superfluorescence, relies on an ensemble of phase-matched dipole oscillators and the suppression of inhomogeneous broadening. Here we report a superradiance platform that combines an optical lattice free from the ac Stark shift and a hollow-core photonic crystal fibre, enabling an extended atom-light interaction over 2 mm free from the Doppler effect. This system allows control of the atom spatial distribution and spectral homogeneity whilst efficiently coupling the radiation field to an optical fibre. The experimentally-observed and theoretically-corroborated temporal, spectral and spatial dynamic behaviours of the superradiance, e.g., superradiance ringing and density-dependent frequency shift, demonstrate a unique interplay between the trapped atoms and the fibre-guided field with multiple transverse modes. Our theory indicates that the resulting temporal evolution of the guided light shows a minimal beam radius of 3.1 mu m which is three times smaller than that of the lowest-loss fibre mode.

2019 - Tailoring modal properties of inhibited-coupling guiding fibers by cladding modification [Articolo su rivista]
Osório, Jonas H.; Chafer, Matthieu; Debord, Benoît; Giovanardi, Fabio; Cordier, Martin; Maurel, Martin; Delahaye, Frédéric; Amrani, Foued; Vincetti, Luca; Gérôme, Frédéric; Benabid, Fetah
abstract

Understanding cladding properties is crucial for designing microstructured optical fibers. This is particularly acute for Inhibited-Coupling guiding fibers because of the reliance of their core guidance on the core and cladding mode-field overlap integral. Consequently, careful planning of the fiber cladding parameters allows obtaining fibers with optimized characteristics such as low loss and broad transmission bandwidth. In this manuscript, we report on how one can tailor the modal properties of hollow-core photonic crystal fibers by adequately modifying the fiber cladding. We show that the alteration of the position of the tubular fibers cladding tubes can alter the loss hierarchy of the modes in these fibers, and exhibit salient polarization propriety. In this context, we present two fibers with different cladding structures which favor propagation of higher order core modes – namely LP11 and LP21 modes. Additionally, we provide discussions on mode transformations in these fibers and show that one can obtain uncommon intensity and polarization profiles at the fiber output. This allows the fiber to act as a mode intensity and polarization shaper. We envisage this novel concept can be useful for a variety of applications such as hollow core fiber based atom optics, atom-surface physics, sensing and nonlinear optics.

2018 - A new approach to the analysis of electromagnetic FEM simulations results at electric field singularities [Articolo su rivista]
Beneventi, Giovanni Betti; Dalre, Massimo; Vincetti, Luca
abstract

A new methodology to the analysis of the results of Finite-Element Modeling (FEM) simulations at electric field singularities is proposed. The method, that can be easily applied in the post-processing phase of the electromagnetic FEM analysis workflow, is based on the weighted averaging of the calculated electric field magnitude within small volumes including the singularity point under investigation. In the paper, the proposed approach is applied to the electrical stress analysis of a high-voltage device modeled by means of a commercial electromagnetic FEM tool. In comparison to the conventional metric of the maximum field evaluation usually adopted for the analysis of electrical stress in insulators, our approach features several advantages: (i) the outcome of the analysis is independent of the numerical grid refinement at the singularity, thus allowing direct comparison of calculated electric field with the material dielectric strength; (ii) the method is robust against slight modifications of the geometrical shape of the singularity; (iii) on the other hand, for a given shape, the analysis outcome responds to significant variations of the singularity size or, in other words, of its sharpness; (iv) in the analysis of high-voltage devices, the approach can be applied for the estimation of the discharge volumes corresponding to different singularity types of different device geometries. In the paper, the new methodology is explained in details and is applied to simple but significant case studies.

2018 - Analytical estimation of confinement loss in tube lattice fibers [Relazione in Atti di Convegno]
Rosa, Lorenzo; Vincetti, Luca
abstract

In this work, we propose an analytical formula for estimating confinement loss in Tube Lattice Fibers. The formula is based on a single-tube model and the comparison with numerical simulations of three TLFs designed to work in the UV, NIR, and THz spectral ranges shows good agreement.

2018 - Mode transformation in an inhibited-coupling guiding asymmetric tubular hollow fiber [Relazione in Atti di Convegno]
Osorio, J. H.; Chafer, M.; Debord, B.; Giovanardi, Fabio; Cordier, M.; Delahaye, F.; Vincetti, L.; Gerome, F.; Benabid, F.
abstract

We report on mode transformation in an asymmetric tubular hollow fiber. We theoretically and experimentally show that LP01 and LP11 modes superposition entails an output profile with unusual spatially-separated orthogonal polarization sites.

2018 - Optimized inhibited-coupling Kagome fibers at Yb-Nd:Yag (8.5 dB/km) and Ti:Sa (30 dB/km) ranges [Articolo su rivista]
Maurel, Martin; Chafer, Matthieu; Amsanpally, Abhilash; Adnan, Muhammad; Amrani, Foued; Debord, Benoit; Vincetti, Luca; Gérôme, Frédéric; Benabid, Fetah
abstract

We report on the development of hypocycloid core-contour inhibited-coupling (IC) Kagome hollow-core photonic crystal fibers (HC-PCFs) with record transmission loss and spectral coverage that include the common industrial laser wavelengths. Using the scaling of the confinement loss with the core-contour negative curvature and the silica strut thickness, we fabricated an IC Kagome HC-PCF for Yb and Nd:Yag laser guidance with record loss level of 8.5 dB/km associated with a 225-nm-wide 3-dB bandwidth. A second HC-PCF is fabricated with reduced silica strut thickness while keeping the hypocycloid core contour. It exhibits a fundamental transmission window spanning down to the Ti:Sa spectral range and a loss figure of 30 dB/km at 750 nm. The fibers’ modal properties and bending sensitivity show these HC-PCFs to be ideal for ultralow-loss, flexible, and robust laser beam delivery.

2018 - Protein detection using hollow-core tube lattice fibers [Relazione in Atti di Convegno]
Giovanardi, F.; Cucinotta, A.; Rozzi, A.; Corradini, R.; Benabid, F.; Vincetti, L.
abstract

In this work we report how tubular lattice hollow core fibers can be successfully used as sensors for proteins such as streptavidin. After a functionalization of the silica surface, a layer of biotin was deposited on the fiber core inner surface. The fiber was than infiltrated with a solution containing streptavidin and a red shift of the fiber transmission spectrum was experimentally observed.

2018 - Thermally-driven mode coupling in multi-core optical fibers [Relazione in Atti di Convegno]
Rosa, L.; Mckee, H.; Poli, F.; Selleri, S.; Vincetti, L.; Cucinotta, A.
abstract

We present results on multi-core fibers (MCFs) for optical amplification/lasing obtained by combined thermal-optical finite-element method (FEM) simulations. Refractive index variation due to quantum defect caused heating is simulated to evaluate thermal dissipationinduced index gradients.

2017 - Experimental optimization of curvature and silica thickness core contour of inhibited-coupling Kagome fibers [Relazione in Atti di Convegno]
Debord, B; Maurel, M; Amsanpally, A; Adnan, M; Gorse, A; Beaudou, B; Blondy, J-M; Vincetti, L; Gérôme, F; Benabid, F
abstract

The dramatic progress in power-scaling of ultra-short pulse (USP) lasers and their continuous expansion use in industrial applications call for flexible and robust beam delivery systems (BDS) over several meters. Recently, a new branch of hollow-core photonic crystal fiber (HC-PCF) based on inhibited coupling (IC) mechanism has been proposed and successfully applied to demonstrate the delivery of milliJoule 600 femtosecond pulses in a several meter long piece and in robustly single-mode fashion. Despite this breakthrough, it is desirable to reduce further the attenuation and enlarge the operating bandwidth of such fiber to increase the capability of the BDS whilst keeping the same delivery performances. In this context, a carefully optimization of the geometrical parameters of the core contour (i.e., the curvature b and the silica thickness t) is studied resulting in the fabrication of new state-of-the-art IC Kagome HC-PCF combining losses less than 10 dB/km for the first time and associated to an enlarged transmission bandwidth able to cover all the entire industrial spectral range.

2017 - Inhibited coupling guiding hollow fibers for label-free DNA detection [Articolo su rivista]
Giovanardi, Fabio; Cucinotta, A.; Vincetti, Luca
abstract

The potentialities in using hollow core tube lattice fibers based on inhibited coupling wave-guiding for label-free DNA detection are numerically investigated and discussed here. The proposed sensing approach does not require any additional transducer component such as Bragg gratings, amplifying techniques such as nanoparticles nor coherent sources. It simply consists of the measurement of the transmittance of a piece of fiber some ten centimeters long. In case of matching DNA sequence, an additional bio-layer is laid down the dielectric-air interface causing a red shift of the transmission spectrum of the fiber. Results show a spectral sensitivity on the bio-layer with shift as high as 42 nm for every 10 nm of bio-layer and robustness against imperfect fiber coupling. The proposed approach can be easily applied to sensing of other complex molecular structures where the presence/absence of analyte can generate or not an additional layer.

2017 - Ultra-low loss (8.5 dB/km @ Yb-laser wavelength range) inhibited-coupling Kagome HC-PCF for laser beam delivery applications [Relazione in Atti di Convegno]
Debord, B.; Maurel, M.; Amsanpally, A.; Adnan, M.; Beaudou, B.; Blondy, J. M.; Vincetti, Luca; Gã©rã´me, F.; Benabid, F.
abstract

The dramatic progress in power-scaling of ultra-short pulse (USP) lasers and their growing use in industrial applications call for flexible and robust beam delivery systems (BDS) over several meters with no temporal or modal distortions. Inhibited coupling (IC) hypocycloid Kagome hollow-core photonic crystal fiber (HC-PCF) has recently proved to be an excellent solution for guiding these USP. In order to reduce further the attenuation of such fiber and then to increase the BDS capabilities, we report on an optimized IC Kagome HC-PCF exhibiting record loss level (8.5dB/km at 1030nm) associated with a 225nm wide 3-dB bandwidth and low bend sensitivity.

2017 - Ultralow transmission loss in inhibited-coupling guiding hollow fibers [Articolo su rivista]
Debord, B.; Amsanpally, A.; Chafer, M.; Baz, A.; Maurel, M.; Blondy, J. M.; Hugonnot, E.; Null, F. Scol; Vincetti, Luca; Gérôme, F.; Benabid, F.
abstract

Attenuation in photonic bandgap guiding hollow-core photonic crystal fiber (HC-PCF) has not beaten the fundamental silica Rayleigh scattering limit (SRSL) of conventional step-index fibers due to strong core-cladding optical overlap, surface roughness at the silica cladding struts, and the presence of interface modes. Hope has been revived recently by the introduction of hypocycloid core contour (i.e., negative curvature) in inhibited-coupling guiding HCPCF. We report on several fibers with a hypocycloid core contour and a cladding structure made of a single ring from a tubular amorphous lattice, including one with a record transmission loss of 7.7 dB/km at ~750 nm (only a factor ~2 above the SRSL) and a second with an ultrabroad fundamental band with loss in the range of 10-20 dB/km, spanning from 600 to 1200 nm. The reduction in confinement loss makes these fibers serious contenders for light transmission below the SRSL in the UV-VIS-NIR spectral range and could find application in high-energy pulse laser beam delivery or gas-based coherent and nonlinear optics.

2017 - 7.7 dB/km transmission loss at 750 nm inhibited-coupling guiding hollowcore photonic crystal fibers [Relazione in Atti di Convegno]
Debord, B.; Amsanpally, A.; Chafer, M.; Baz, A.; Maurel, M.; Blondy, J. M.; Hugonnot, E.; Scol, F.; Vincetti, L.; Ge´roˆme, F.; Benabid, F.
abstract

The last few years have seen the emergence of a new class of hollow-core photonic crystal fibers (HC-PCF) no longer relying on photonic bandgap guidance but on inhibited-coupling (IC) mechanism. The first specie of this fiber family took the form of Kagome-lattice [1]. The guiding rule for enhancement of such a guidance (minimizing the coupling between the core mode and cladding mode, i.e (φclad |Δn2| φcore) → 0) led to the introduction in 2010 of hypocycloidal (or negative curvature) core contour [2] in Kagome HC-PCFs where record loss values (8.5 dB/km at 1 μm [3]) have been demonstrated. Thanks to this design, three reasons explain the reduction of such a criterion: i) the HE11 mode field spatial overlap with silica is reduced to the tangent sections of the inner cups of the hypocycloid contour, ii) the larger perimeter of the hypocycloid contour results in a higher azimuthal-like number in the silica core-surround modes and hence, stronger transverse phase-mismatch with the core mode. iii) the spatial overlap between the core-mode with connecting nodes supporting low azimuthal number modes is strongly reduced. Recently, another hollow-core fiber design has been proposed that fully fulfils the mentioned features for IC guidance, relying on a tubular lattice with a one ring of isolated (with no connecting nodes) thin glass tubes [4]. Here, we report on the fabrication and characterization of ultra-low loss single-ring tubular lattice HC-PCFs (SR HC-PCF) guiding m the UV-VIS-NIR with absolute record loss value for HC-PCF at 750 nm with 7.7 dB/km, supplanting bandgap fiber performances in this spectral range.

2016 - Empirical formulas for calculating loss in hollow core tube lattice fibers [Articolo su rivista]
Vincetti, Luca
abstract

In this paper scaling laws governing loss in hollow core tube lattice fibers are numerically investigated and discussed. Moreover, by starting from the analysis of the obtained numerical results, empirical formulas for the estimation of the minimum values of confinement loss, absorption loss, and surface scattering loss inside the transmission band are obtained. The proposed formulas show a good accuracy for fibers designed for applications ranging from THz to ultra violet band.

2016 - Fusion splice between tapered inhibited coupling hypocycloid-core Kagome fiber and SMF [Articolo su rivista]
Zheng, Ximeng; Debord, Benoît; Vincetti, Luca; Beaudou, Benoît; Gérôme, Frédéric; Benabid, Fetah
abstract

We report for the first time on tapering inhibited coupling (IC) hypocycloid-core shape Kagome hollow-core photonic crystal fibers whilst maintaining their delicate core-contour negative curvature with a down-ratio as large as 2.4. The transmission loss of down-tapered sections reaches a figure as low as 0.07 dB at 1550 nm. The tapered IC fibers are also spliced to standard SMF with a total insertion loss of 0.48 dB. These results show that all-fiber photonic microcells with the ultra-low loss hypocycloid corecontour Kagome fibers is now possible.

2016 - PLASMONIC NANOANTENNA FOR POSSIBLE CMOS INTEGRATION [Poster]
Polemi, Alessia; Vincetti, Luca
abstract

Plasmonic nanoantennas have gained interest in several environments like integrated photonics, biosensing, microscopy and solar cells, due to their capability in collecting and conveying the electromagnetic radiation in the visible and in the near visible regions. However, examples of antennas applied to integrated circuits are conspicuously rare even if they are able to provide a solution to the bandwidth shortage problem. In this work I have developed a new plasmonic nanoantenna configuration able to be easily coupled with a transmission line in order to enable the direct connection with plasmonic modulators and demodulators. Furthermore, the antenna shows a tunable double resonance that allows for bidirectional communications without the use of complex TDD techniques. The size of the antenna and the materials employed are all suitable for future CMOS integration.

2016 - 7.7 dB/km losses in inhibited coupling hollow-core photonic crystal fibers [Relazione in Atti di Convegno]
Debord, B.; Amsanpally, A.; Chafer, M.; Baz, A.; Vincetti, Luca; Blondy, J. M.; Gérôme, F.; Benabid, F.
abstract

Several UV-VIS-NIR guiding HC-PCFs are fabricated. One exhibits a loss of 7.7 dB/km at ∼750 nm and guides down to 220 nm. A second exhibits ultra-broad fundamental-band with losses < 20 dB/km over 600-1200 nm.

2015 - Fano Resonance in Inhibited Coupling Kagome Fiber [Relazione in Atti di Convegno]
Amsanpally, Abhilash; Debord, Benoît; Alharbi, Meshaal; Ilinova, Ekaterina; Vincetti, Luca; Gérôme, Frédéric; Benabid, Fetah
abstract

We report on the first experimental observation of Fano resonances in inhibitedcoupling guiding Kagome fiber. A high-spectral resolution fiber-transmission showed the typical Fano asymmetric feature and a high dynamic-range near-field imaging resolved the core-cladding coupling.

2015 - Fano resonance in inhibited coupling Kagome fiber [Relazione in Atti di Convegno]
Amsanpally, A.; Debord, B.; Alharbi, M.; Ilinova, E.; Vincetti, L.; Gerome, F.; Benabid, F.
abstract

We report on the first experimental observation of Fano resonances in inhibited-coupling guiding Kagome fiber. A high-spectral resolution fiber-transmission showed the typical Fano asymmetric feature and a high dynamic-range near-field imaging resolved the core-cladding coupling.

2015 - Inhibited Coupling Kagome Fibers with Ultra-large Hollow-core Size for High Energy Ultrafast Laser Applications [Relazione in Atti di Convegno]
Debord, Benoît; Amsanpally, Abhilash; Alharbi, Meshaal; Vincetti, Luca; Blondy, Jean Marc; Gérôme, Frédéric; Benabid, Fetah
abstract

We report on enlarged hollow-core diameter inhibited coupling Kagome fibers with record loss of 100 dB/km and ppm power overlap with silica surround, suitable for high energy ultrafast laser handling.

2015 - Reconfigurable RF Energy Harvester with Customized Differential PCB Antenna [Articolo su rivista]
Bertacchini, Alessandro; Larcher, Luca; Maini, Moreno; Vincetti, Luca; Scorcioni, Stefano
abstract

In this work, a RF Energy harvester comprised of a differential RF-DC CMOS converter realized in ST130nm CMOS technology and a customized broadband PCB antenna with inductive coupling feeding is presented. Experimental results show that the system can work with different carrier frequencies and thanks to its reconfigurable architecture the proposed converter is able to provide a regulated output voltage of 2 V over a 14 dB of RF input power range. The conversion efficiency of the whole system peaks at 18% under normal outdoor working conditions.

2015 - Scaling Laws in Tube Lattice Fibers [Relazione in Atti di Convegno]
Masruri, Masruri; Cucinotta, Annamaria; Vincetti, Luca
abstract

Scaling laws of confinement loss and dielectric overlap in circularly arranged tube lattice fibers are numerically analyzed. Confinement loss scales as the 4.5 power of wavelengthcore size ratio whereas dielectric overlap dependence is weaker.

2015 - Scaling laws in tube lattice fibers [Relazione in Atti di Convegno]
Masruri, M.; Cucinotta, A.; Vincetti, L.
abstract

Scaling laws of confinement loss and dielectric overlap in circularly arranged tube lattice fibers are numerically analyzed. Confinement loss scales as the 4.5 power of wavelength-core size ratio whereas dielectric overlap dependence is weaker.

2015 - Splicing Tapered Inhibited-coupling Hypocycloid-core Kagome Fiber to SMF Fibers [Relazione in Atti di Convegno]
Ximeng, Zheng; Debord, Benoît; Alharbi, Meshaal; Vincetti, Luca; Gérôme, Frédéric; Benabid, Fetah
abstract

We report on tapered inhibited coupling Kagome-fiber with a down-ratio as large as 2.4 while maintaining the hypocycloid-core shape. The insertion-loss of SMF spliced to tapered Kagomefiber was measured with minimum of 0.48dB at 1550nm.

2015 - Splicing tapered inhibited-coupling hypocycloid-core Kagome fiber to SMF fibers [Relazione in Atti di Convegno]
Zheng, X. M.; Debord, B.; Alharbi, M.; Vincetti, L.; Gerome, F.; Benabid, F.
abstract

We report on tapered inhibited coupling Kagome-fiber with a down-ratio as large as 2.4 while maintaining the hypocycloid-core shape. The insertion-loss of SMF spliced to tapered Kagome-fiber was measured with minimum of 0.48dB at 1550nm.

2015 - Triple-cup hypocycloid-core inhibited coupling Kagome hollow-core photonic crystal fiber [Relazione in Atti di Convegno]
Vincetti, L.; Debord, B.; Alharbi, M.; Gerome, F.; Benabid, F.
abstract

We report on design and fabrication of a new hypocycloid core-contour Kagome HC-PCF based on a triangular-like shaped core exhibiting smaller effective area and comparable confinement loss than previous hypocycloid core-contour Kagome fibers.

2015 - Triple-cup Hypocycloid-Core Inhibited-Coupling Kagome Hollow-Core Photonic Crystal Fiber [Relazione in Atti di Convegno]
Vincetti, Luca; Debord, Benoît; Alharbi, Meshaal; Gérôme, Frédéric; Benabid, Fetah
abstract

We report on design and fabrication of a new hypocycloid core-contour Kagome HCPCF based on a triangular-like shaped core exhibiting smaller effective area and comparable confinement loss than previous hypocycloid core-contour Kagome fibers.

2015 - Ultra-Large Core Size Hypocycloid-Shape Inhibited Coupling Kagome Fibers for High-Energy Laser Beam Handling [Articolo su rivista]
Debord, Benoit; Amsanpally, Abhilash; Alharbi, Meshaal; Vincetti, Luca; Blondy, Jean Marc; Gerome, Frederic; Benabid, Fetah
abstract

We report on the fabrication and characterization of 19-cell hypocycloid-shape Kagome fibers with core size larger than 100 μm. These inhibited coupling fibers present low propagation loss (100 dB/km) over broad transmission range with low chromatic dispersion combined with ultra-low power overlap with silica surround, making them an efficient solution for ultra-high power laser handling, ultra-fast laser delivery, and plasma photonics applications.

2014 - Circular Tube lattice fibers for terahertz applications [Relazione in Atti di Convegno]
Masruri, Masruri; Cucinotta, Annamaria; Selleri, Stefano; Vincetti, Luca
abstract

The development of low loss, broadband, small size and flexible waveguides has become a key issue in terahertz (THz) research due to the poor characteristics of both dielectrics and metals in this frequency range. Hollow core circular tube lattice fibers (HC-CTLFs) have been recently proposed and experimentally demonstrated to match many of these conditions. They are composed of a hollow core surrounded by a circular arrangement of dielectric tubes. CTLFs guide via Inhibited Coupling (IC) which doesn't rely on photonic bandgap and the confinement depends on a strong reduction of the coupling between core modes and cladding modes. The losses in CTLF can be divided into the confinement loss and the absorption loss. Both of them can be reduced by enlarging the fiber core size, but this makes the fiber big and hardly flexible. For an optimized design of the fiber, scaling law analysis plays an important role in determining the best trade-off between low loss and small size. Here the dependence of the confinement and absorption loss on frequency and core radius are numerically investigated. Results show that confinement loss exhibits a stronger dependence of core size and frequency with respect to other hollow core fibers proposed for THz waveguiding such as Kagome, Bragg, and Tube fibers as well as to dielectric absorption loss.

2014 - Confinement loss scaling law analysis in tube lattice fibers for terahertz applications [Relazione in Atti di Convegno]
Masruri, M.; Vincetti, Luca; Molardi, C.; Coscelli, E.; Cucinotta, A.; Selleri, S.
abstract

The development of low loss, small size and flexible waveguides is one of the most challenging issues of THz research due to the poor characteristics of both metal and dielectrics in this frequency range. Hollow core tube lattice fibers (HC-TLFs) have been recently proposed and experimentally demonstrated to overcome this problem. However, they require very large hollow core size leading to big and hardly flexible fibers. Scaling law analysis plays an important role in determining the best trade-off between low loss and small fiber diameter. The dependence of the confinement on frequency and core radius are here numerically investigated. Results show that confinement loss exhibits a stronger dependence on core size and frequency with respect to other hollow core fibers proposed for THz waveguiding, such as Bragg, Tube, and Kagome fibers.

2014 - Inhibited coupling hollow-core photonic crystal fiber [Relazione in Atti di Convegno]
Benabid, F.; Gérôme, F.; Vincetti, Luca; Debord, B.; Alharbi, M.; Bradley, T.
abstract

We review the recent progress on the enhanced inhibited coupling in kagome hollow-core photonic crystal fiber by introducing negative curvature in the fiber-core shape. We show that increasing the hypocycloid contour curvature leads to a dramatic decrease in transmission loss and optical overlap with the silica surround and to a single modedness. Fabricated hypocycloid-core hollow-core photonic crystal fibers with a transmission loss in the range of 20-40 dB/km and for a spectral range of 700 nm-2000 nm have now become typical.

2014 - Integrated RF-DC converter and PCB antenna for UHF wireless powering applications [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, M.; Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro; Tacchini, Alessandro
abstract

In this work, a broadband differential RF-DC CMOS converter realized in CMOS 130 nm technology with a customized PCB antenna with inductive coupling feeding for RF energy scavenging is presented. Experimental results show that output DC voltage higher than 1V from 800MHz to 970MHz can be obtained with a load of 1kohm.

2014 - Lamb-Dicke spectroscopy of atoms in a hollow-core photonic crystal fibre [Articolo su rivista]
Okaba, S.; Takano, T.; Benabid, F.; Bradley, T.; Vincetti, Luca; Maizelis, Z.; Yampol'Skii, V.; Nori, F.; Katori, H.
abstract

Unlike photons, which are conveniently handled by mirrors and optical fibres without loss of coherence, atoms lose their coherence via atom-atom and atom-wall interactions. This decoherence of atoms deteriorates the performance of atomic clocks and magnetometers, and also hinders their miniaturization. Here we report a novel platform for precision spectroscopy. Ultracold strontium atoms inside a kagome-lattice hollow-core photonic crystal fibre are transversely confined by an optical lattice to prevent atoms from interacting with the fibre wall. By confining at most one atom in each lattice site, to avoid atom-atom interactions and Doppler effect, a 7.8-kHz-wide spectrum is observed for the 1S0-3 P1 (m=0) transition. Atoms singly trapped in a magic lattice in hollow-core photonic crystal fibres improve the optical depth while preserving atomic coherence time.

2014 - Multi-meter fiber-delivery and pulse self-compression of milli-Joule femtosecond laser and fiber-aided laser-micromachining [Articolo su rivista]
Debord, B.; Alharbi, M.; Vincetti, Luca; Husakou, A.; Fourcade Dutin, C.; Hoenninger, C.; Mottay, E.; Gérôme, F.; Benabid, F.
abstract

We report on damage-free fiber-guidance of milli-Joule energylevel and 600-femtosecond laser pulses into hypocycloid core-contour Kagome hollow-core photonic crystal fibers. Up to 10 meter-long fibers were used to successfully deliver Yb-laser pulses in robustly single-mode fashion. Different pulse propagation regimes were demonstrated by simply changing the fiber dispersion and gas. Self-compression to ̃50 fs, and intensity-level nearing petawatt/cm2 were achieved. Finally, free focusingoptics laser-micromachining was also demonstrated on different materials.

2014 - Ultra low-loss hypocycloid-core Kagome hollow-core photonic crystal fiber for green spectral-range applications [Articolo su rivista]
Debord, B.; Alharbi, M.; Benoît, A.; Ghosh, D.; Dontabactouny, M.; Vincetti, Luca; Blondy, J. M.; Gérôme, F.; Benabid, F.
abstract

We report on the development of a hypocycloidal-core Kagome hollow-core photonic crystal fiber guiding, with low transmission loss in the 450-650 nm visible spectral range. Transmission loss records have been achieved with 70 dB/km at 600 nm, and 130 dB/km at 532 nm. As a demonstration of the fiber potential applications, we report on a compact 600 THz wide Raman comb generator, centered around 532 nm, and on a 10 W average power frequency-doubled Yb-fiber picosecond laser beam delivery, along with its use for organic material laser microprocessing.

2013 - An Integrated RF Energy Harvester for UHF Wireless Powering Applications [Relazione in Atti di Convegno]
Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro; Vincetti, Luca; Maini, Moreno
abstract

A RF energy harvester comprised of an integrated differential RF-DC converter and a differential PCB custom antenna is presented for wireless powering applications in the UHF band. The RF-DC converter, based on a reconfigurable voltage rectifier directly connected to a matched PCB antenna, is designed for high efficiency and sensitivity. Prototypes of the RF-DC converter realized in CMOS 130nm technology show a -16dBm sensitivity and a 60% peak efficiency. The RF-DC converters operate within the -16dBm÷0dBm input power range with an efficiency which remains above the 40% for more than 10dB. The RF energy harvester operates on the 840MHz÷975MHz band thanks to the ad-hoc designed wide-band differential antenna.

2013 - Cladding effect on confinement and bend losses in hypocycloid-core Kagome HC-PCF [Relazione in Atti di Convegno]
M. l., Alharbi; T., Bradley; B., Debord; C., Fourcade Dutin; D., Ghosh; Vincetti, Luca; F., Gérôme; F., Benabid
abstract

We report on numerical and experimental results on the influence of cladding ring number in hypocycloid-core Kagome HC-PCF. The number of rings has moderate effect on confinement loss whereas strong reduction in bend loss is demonstrated.

2013 - Cups curvature effect on confinement loss in hypocycloid-core Kagome HC-PCF [Relazione in Atti di Convegno]
B., Debord; M., Alharbi; T., Bradley; C., Fourcade Dutin; Y., Wang; Vincetti, Luca; F., Gérôme; F., Benabid
abstract

We report on numerical and experimental results showing the influence of cups curvature of hypocycloid-core Kagome HC-PCF on the confinement loss. Fabricated fibers with circular cups demonstrate record loss-level of 40 dB/km at 1064 nm.

2013 - Elliptical hollow core tube lattice fibers for terahertz applications [Articolo su rivista]
Vincetti, Luca; Setti, Valerio
abstract

Hollow core microstructured fibers whose cladding is composed by an elliptical arrangement of circular dielectric tubes are numerically investigated. Birefringence, differential group delay, and polarization dependent loss are evaluated for different values of ellipticity in order to quantify its effect on the two polarizations of the fundamental core mode. All these parameters have a minimum at the center of each transmission window and they assume maximum values at the edges. In particular, the birefringence goes always to zero irrespective of ellipticity. This proves that tube lattice fibers are strongly immune against unwanted core shape deformation, in particular when the working frequency is close to the center of the transmission windows. On the other hand they are not suitable to obtain polarization maintaining fibers.

2013 - Flexible tube lattice fibers for terahertz applications [Articolo su rivista]
V., Setti; Vincetti, Luca; A., Argyros
abstract

In this paper a flexible hollow core waveguide for the terahertz spectral range is demonstrated. Its cladding is composed of a circular arrangement of dielectric tubes surrounded by a heat-shrink jacket that allows the fiber to be flexible. Characterization of straight samples shows that the hollow core allows the absorption caused by the polymethylmethacrylate tubes of the cladding to be reduced by 31 times at 0.375 THz and 272 times at 0.828 THz with respect to the bulk material, achieving losses of 0.3 and 0.16 dB/cm respectively. Bending loss is also experimentally measured and compared to numerical results. For large bending radii bending loss scales as R−2b, whereas for small bending radii additional resonances between core and cladding appear. The transmission window bandwidth is also shown to shrink as the bending radius is reduced. An analytical model is proposed to predict and quantify both of these bending effects.

2013 - Hypocycloid-shaped hollow-core photonic crystal fiber Part I: Arc curvature effect on confinement loss [Articolo su rivista]
B., Debord; M., Alharbi; T., Bradley; C., Fourcade Dutin; Y. Y., Wang; Vincetti, Luca; F., Gérôme; F., Benabid
abstract

We report on numerical and experimental studies showing the influence of arc curvature on the confinement loss in hypocycloid-core Kagome hollow-core photonic crystal fiber. The results prove that with such a design the optical performances are strongly driven by the contour negative curvature of the core-cladding interface. They show that the increase in arc curvature results in a strong decrease in both the confinement loss and the optical power overlap between the core mode and the silica core-surround, including a modal content approaching true single-mode guidance. Fibers with enhanced negative curvature were then fabricated with a record loss-level of 17 dB/km at 1064 nm.

2013 - Hypocycloid-shaped hollow-core photonic crystal fiber Part II: Cladding effect on confinement and bend loss [Articolo su rivista]
M., Alharbi; T., Bradley; B., Debord; C., Fourcade Dutin; D., Ghosh; Vincetti, Luca; F., Gérôme; F., Benabid
abstract

We report on numerical and experimental studies on the influence of cladding ring-number on the confinement and bend loss in hypocycloid-shaped Kagome hollow core photonic crystal fiber. The results show that beyond the second ring, the ring number has a minor effect on confinement loss whereas the bend loss is strongly reduced with the ringnumber increase. Finally, the results show that the increase in the cladding ring-number improves the modal content of the fiber.

2013 - Milli-Joule femtosecond laser-pulse delivery and compression in hypocycloid core Kagome HC-PCF [Relazione in Atti di Convegno]
C., Fourcade Dutin; B., Debord; M., Dontabactouny; C., Hönninger; E., Mottay; Vincetti, Luca; F., Gérôme; F., Benabid
abstract

Milli-Joule energy and 600-femtosecond Yb-laser pulses were delivered in several meter Kagome hollow-core-photonic-crystal-fibers in robustly single-mode fashion. Self-compression to 50fs, and intensity-level of petawatt/cm2 were achieved. Free focusing-optics laser-micromachining is demonstrated.

2013 - Multi-meter fiber-delivery and compression of milli-joule femtosecond laser and fiber-aided micromachining [Relazione in Atti di Convegno]
Debord, B.; Dontabactouny, M.; Alharbi, M.; Fourcade-Dutin, C.; Honninger, C.; Mottay, E.; Vincetti, L.; Gerome, F.; Benabid, F.
abstract

Up to 10 meter-long Kagome hollow-core-photonic-crystal-fibers were used to successfully deliver Yb-laser pulses with milli-Joule energy-level and 600-femtosecond pulsewidth in robustly single-mode fashion. Self-compression to ~50fs, and intensity-level nearing petawatt/cm2 were achieved. Free focusing-optics laser-micromachining is demonstrated on different materials. © OSA 2013.

2013 - Single-Ended Broadband Antenna for Radiofrequency Energy Harvesting [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, M.; Bompani, M.; Larcher, Luca; Scorcioni, Stefano; Bertacchini, Alessandro; Grossi, D.; Tacchini, Alessandro
abstract

A single-ended broadband UHF antenna with high inductive input impedance for radiofrequency energy harvesting is here presented. It consists of a small feeding loop and a conical radiating monopole. A prototype has been fabricated on a FR4 substrate and tested. Experimental results show a -3dB power transmission bandwidth of about 130MHz (860MHz−990MHz).

2012 - Analysis of the Confinement Loss in Kagome Fibers [Abstract in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

Hollow-core Inhibited Coupling Fibers (ICFs) have been widely analyzed in these years in order to minimize their Con¯nement Loss (CL).

2012 - Bending loss in tube lattice fibers for terahertz applications [Relazione in Atti di Convegno]
V., Setti; Vincetti, Luca; A., Argyros
abstract

Spectral properties of straight hollow core Circular Tube Lattice Fibers in the THz regime are analyzed both numerically and experimentally. Good agreement between simulated and manufactured fibers is found proving that these fibers have high potential for THz applications. Finally, bending properties are investigated with FEM simulations, showing that low-order transmission windows are strongly robust against extra losses due to the bending.

2012 - Birefringence in Elliptical Tube Fibers [Abstract in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

The dispersion and loss properties of elliptical hollow core tube fibres are analyzed.

2012 - Broadband Printed Antenna for Radiofrequency Energy Harvesting [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; E., Pinotti; Larcher, Luca; S., Scorcioni; Bertacchini, Alessandro; D., Grossi; A., Tacchini
abstract

In this work a broadband UHF antenna with high inductive input impedance for radiofrequency energy harvesting is presented. It consists of a small feeding loop and a biconical radiating dipole. A prototype has been fabricated on a FR4 substrate and tested. Experimental results show a - 3dB power transmission bandwidth of about 135MHz (840MHz−975MHz).

2012 - Componenti Ottici e Fotonici [Monografia/Trattato scientifico]
S., Selleri; Vincetti, Luca; A., Cucinotta
abstract

La Fotonica, come disciplina di ricerca, nasce negli anni sessanta con l’invenzione e la produzione dei primi laser. Lo sviluppo di queste sorgenti fu seguito negli anni 70 dall’utilizzo su larga scala delle fibre ottiche come mezzo per trasmettere l’informazione tramite fasci di luce. Negli anni successivi la ricerca scientifica e il continuo progresso tecnologico nel settore portarono ad una vera e propria rivoluzione nelle telecomunicazioni. L’incontro tra la fotonica ed altre discipline ha poi aperto orizzonti nuovi, qualche decina di anni fa semplicemente inimmaginabili. Questo testo, pur raccogliendo materiale pensato per i futuri ingegneri delle telecomunicazioni ed ingegneri elettronici che dovranno affrontare la progettazione di componenti e sottosistemi su portante ottica, introduce nozioni base per avvicinarsi anche a discipline diverse con cui la fotonica possa proficuamente interagire.

2012 - Confinement Loss in Kagome and Tube Lattice Fibers: Comparison and Analysis [Articolo su rivista]
Vincetti, Luca; Setti, Valerio
abstract

In this paper, a thorough numerical analysis of the confinement loss in kagome and tube lattice fibers is presented. The results show that the confinement loss strongly depends on the shape of the struts composing the core boundary and the cladding. This explains why confinement loss in kagome fibers is much higher than in tube lattice ones. In fact, the closer to a perfectly circular arc the struts, the lower the confinement loss. For this reason, struts shape must be carefully controlled during the fabrication process.

2012 - Electromagnetic Analysis of PD Detection in GIS Systems [Relazione in Atti di Convegno]
A., Tacchini; D., Grossi; Vincetti, Luca; Maini, Moreno; S., Serra; M., Fattori; L., Sandrolini
abstract

In this work the radiation of the electromagnetic field due to partial discharges throughout the insulation spacer of Gas Insulated Switchgears is investigated. Radiation can be described in terms of resonant modes of the slot between the metallic bolts. Moreover other resonant modes due to the spacer flanges are observed and investigated for the first time.

2012 - Electromagnetic analysis of the radiated field by Gas Insulated Switchgears for fault detection [Relazione in Atti di Convegno]
A., Tacchini; D., Grossi; Vincetti, Luca; Maini, Moreno; S., Serra; M., Fattori; L., Sandrolini
abstract

In this work a broadband UHF antenna with high inductive input impedance for radiofrequency energy harvesting is presented. It consists of a small feeding loop and a biconical radiating dipole. A prototype has been fabricated on a FR4 substrate and tested. Experimental results show a - 3dB power transmission bandwidth of about 135MHz (840MHz−975MHz).

2012 - Elliptical hollow tube waveguides [Relazione in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

Dispersion and loss properties of hollow core tube fibers with elliptical cross section are numerically investigated. Results show unusual characteristics. For example, the birefringence always goes to zero in the middle of the low loss region irrespectively of the ellipticity and it always assume opposite sign approaching the two edges of the low loss region.

2012 - Extra loss due to Fano resonances in inhibited coupling fibers based on a lattice of tubes [Articolo su rivista]
Vincetti, Luca; Setti, Valerio
abstract

Confinement loss of inhibited coupling fibers with a cladding composed of a lattice of tubes of various shapes is theoretically and numerically investigated. Both solid core and hollow core are taken into account. It is shown that in case of polygonal shaped tubes, confinement loss is affected by extra loss due to Fano resonances between core modes and cladding modes with high spatial dependence. This explains why hollow core Kagome fibers exhibit much higher confinement loss with respect to tube lattice fibers and why hypocycloid core cladding interfaces significantly reduce fiber loss. Moreover it is shown that tube deformations, due for example to fabrication process, affect fiber performances. A relationship between the number of polygon sides and the spectral position of the extra loss is found. This suggests general guide lines for the design and fabrication of fibers free of Fano resonance in the spectral range of interest.

2012 - Fano resonances in Kagome fibers [Relazione in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

Confinement Loss of microstructured fibers whose cladding is composed by a triangular arrangement of tubes of various shapes is theoretically and numerically investigated. Kagome Fibers belong from this family of fibers with cladding tubes with hexagonal shape. The shape of the cladding tubes is proved to strongly affect the performance of the microstructured fiber. In order to understand the reasons for this behavior, the spectral properties of the tubes that constitute the cladding are investigated first. It is proved that also these tubes suffer from additional Fano Resonances when they are given a polygonal shape. It is proved that, by using the analytical model developed for the stand alone polygonal tubes, it is possible to predict the spectral position of Fano Resonances also in microstructured fibers. This is extremely important since it suggest new ways to reduce confinement loss in kagome fibers and microstructured fibers in general.

2012 - Fano Resonances in Polygonal Tube Fibers [Articolo su rivista]
Vincetti, Luca; Setti, Valerio
abstract

In this paper, the dispersion and the confinement loss properties of polygonal tube fibers are investigated. Fano resonances between the hollow core modes and the high order dielectric modes are found inside transmission bands. A theoretical model based on the approximation of the polygonal tube as a perturbed circular one is proposed. The model is able to predict number and spectral position of the Fano resonances. It is shown that there always is a lower bound condition on the number of sides of the polygonal fiber which guarantees the absence of Fano resonances in a given frequency range. Numerical results are given in order to support the model.

2011 - Confinement Loss of Tube Lattice and Kagome Fibers [Relazione in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

Confinement loss of two kinds of broad band hollow core fibers, the tube lattice fibers and the kagomé fibers, are numerically investigated and compared.

2010 - Analysis of the Waveguiding Mechanism in Tube Lattice Fibers [Relazione in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

In this paper, waveguiding mechanism and modal characteristics of hollow core ber made of a regular arrangement of dielectric tubes is investigated. A simply analytical model to predict dispersion curves and low loss regions is proposed and numerically validated.

2010 - Fibre ottiche a nucleo cavo con simmetria ottagonale per applicazioni Terahertz [Relazione in Atti di Convegno]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

A new hollow core fiber for THz applications consisting of dielectric tubes arranged with a octagonal symmetry is presented. Numerical results show that this fiber exhibits an effectively single mode propagation with lower propagation loss with respect to fiber with hexagonal symmetry previously proposed.

2010 - Numerical Analysis of Propagating and Radiating Properties of Hollow Core Photonic Band Gap Fibres for THz Applications [Articolo su rivista]
Vincetti, Luca; Polemi, Alessia
abstract

Hollow core photonic bandgap fibres (HC-PBGFs) are numerically investigated in order to obtain low loss wave-guiding and good aperture field distribution in the terahertz region (0.1-10 THz) of the electromagnetic spectrum. The purity of the aperture field distribution at the HC-PBGF section combined with low loss propagation and high coupling efficiency with free-space propagating Gaussian beams suggest a possible employment of such a structure as aperture antennas, for possible feed systems in THz applications and in THz wireless sensing.

2010 - Octagonal Large-Mode-Area Leakage Channel Fiber with Reduced Bending Loss [Relazione in Atti di Convegno]
Rosa, Lorenzo; K., Saitoh; M., Koshiba; F., Poli; A., Cucinotta; S., Selleri; Vincetti, Luca; M., Pal; M., Paul; D., Ghosh; S., Bhadra
abstract

We investigate a novel design for high-power large-modearea leakage channel fibers (LCFs) with a single octagonal dual-diameter air-hole ring encircling a nine-cell pure-silica core, having a tenfold differential mode loss and increased resistance to bending.

2010 - Octagonal large-mode-area leakage channel fiber with reduced bending loss [Relazione in Atti di Convegno]
Rosa, L.; Saitoh, K.; Koshiba, M.; Poli, F.; Cucinotta, A.; Selleri, S.; Vincetti, L.; Pal, M.; Paul, M.; Ghosh, D.; Bhadra, S.
abstract

We investigate a novel design for high-power large-mode-area leakage channel fibers (LCFs) with a single octagonal dual-diameter air-hole ring encircling a nine-cell pure-silica core, aving a tenfold differential mode loss and increased resistance to bending. © 2010 Optical Society of America.

2010 - Propagating and radiating properties of Broadband Hollow Core fibers in Terahertz spectral region [Relazione in Atti di Convegno]
Setti, Valerio; Vincetti, Luca; Polemi, Alessia
abstract

In this paper Hollow Core Microstructured Fibers consisting of a regular arrangement of dielectric tubes of Teflon are numerically investigated in order to obtain efficient and highly directive aperture antennas for Terahertz applications. The good aperture field distribution allow to obtain high power coupling coefficient with freely propagationg gaussian beams, narrow beamwidth and low side lobe level over a wide range of frequencies as wide as 1.5THz centered at 2.25 THz. Antenna performances are not affected by fiber dimension allowing a more flexible design in order to better meet the requirements of a particular application. An array configuration of fibers arranged in a hexagonal lattice have been also investigated.

2010 - Realistic squared-rods circular F-doped large-mode-area leakage channel fibers with low bending loss [Relazione in Atti di Convegno]
Rosa, Lorenzo; Saitoh, K.; Koshiba, M.; Pal, M.; Paul, M.; Ghosh, D.; Mahanty, T.; Bhadra, S.; Vincetti, Luca; Selleri, S.
abstract

We investigate realistic all-glass large-mode-area leakage channel fibers (LCFs) with a single down-doped-silica circular flattened-rod ring, engineering the silica bridge width for effectively single-mode behavior and reduced bending loss.

2010 - Single-mode propagation in triangular tube lattice hollow-core terahertz fibers [Articolo su rivista]
Vincetti, Luca
abstract

The mode properties of hollow-core fibers with a cladding formed by a periodic arrangement of dielectric tubes in a triangular lattice for THz applications are numerically investigated. The fiber supports a high number of modes. Effectively single-mode operation can be obtain by reducing the core size, but at the expense of high fundamental mode propagation loss. Single-mode propagation can be obtained by exciting the fiber with a linear polarized gaussian beam with proper spot size.

2010 - Terahertz Tube Lattice Fibers With Octagonal Symmetry [Articolo su rivista]
Vincetti, Luca; Setti, Valerio; Zoboli, Maurizio
abstract

A new hollow core fiber for terahertz applications consisting of dielectric tubes arranged with an octagonal symmetry is presented. Simulation results have shown that this fiber exhibits an effectively single-mode propagation with lower propagation loss with respect to hollow core fibers with a hexagonal symmetry. The suppression of higher order modes is due to a better phase-matching condition with cladding modes propagating into the hollow core of tubes. In particular, by using tubes with 44-μm thickness and outer diameters as low as 0.5 mm, a rejection of high order modes higher than 20 dB/m and fundamental mode propagation loss lower than 5 dB/m from 2.30 to 2.85 THz can be obtained.

2010 - Waveguiding mechanism in tube lattice fibers [Articolo su rivista]
Vincetti, Luca; Setti, Valerio
abstract

Waveguiding mechanism and modal characteristics of hollow core fibers consisting of a single or a regular arrangement of dielectric tubes are investigated. These fibers have been recently proposed as low loss, broadband THz waveguides. By starting from a description in terms of coupling between air and dielectric modes in a single tube waveguide, a simple and useful model is proposed and numerically validated. It is able to predict dispersion curves, high and low loss spectral regions, and the conditions to ensure the existence of low loss regions. In addition, it allows a better understanding of the role of the geometrical parameters and of the dielectric refractive index. The model is then applied to improve the tradeoff between low loss and effectively single mode propagation, showing that the best results are obtained with a heptagonal arrangement of the tubes.

2009 - Fibre microstrutturate a nucleo cavo per applicazioni nella gamma dei Terahertz [Relazione in Atti di Convegno]
Vincetti, Luca; Polemi, Alessia; Zoboli, Maurizio
abstract

Propagation characteristics of a hollow core microstructured fibre in the THz regime are numerically investigated. The fibre cladding consists of a triangular lattice formed by a periodic arrangement of Teflon dielectric tubes. Low loss and low dispersion frequencyranges can be tuned out just by changing the tubes thickness, irrespectively of their diameter.

2009 - Hollow core fibre for THz applications [Relazione in Atti di Convegno]
Vincetti, Luca; Polemi, Alessia
abstract

This work is focused on the analysis of hollow core photonic band gap fibres (HC-PBGFs) for THz applications. Waveguide design in this spectral region is a major challenge due to the high conductivity losses of metals and high absorption of the dielectrics. HC-PBGFs are dielectric waveguides in which the power fraction propagating in the dielectric is very low, and losses due to material absorption are dramatically reduced. HC-PBGFs have been proposed and developed from the end of 90's for applications in visible and near infrared (NIR) spectrum, and in few years propagation losses have been dramatically reduced from tens of dB/m to few dB/Km.

2009 - Hollow core photonic band gap fiber for THz applications [Articolo su rivista]
Vincetti, Luca
abstract

In this article, a hollow core photonic band gap fiber is numerically investigated to obtain low-loss waveguiding in the terahertz region (0.1-10 THz) of the electromagnetic spectrum. Waveguide design in this spectral region is an arduous challenge due to the high-conductivity losses of metals and high-absorption of the dielectrics. Numerical results show the possibility to reach propagation loss two decades lower than the bulk absorption losses of the material used to fabricate the fiber, and low dispersion over a wide range of wavelength.

2009 - Numerical analysis of plastic hollow core microstructured fiber for Terahertz applications [Articolo su rivista]
Vincetti, Luca
abstract

Propagation loss and dispersion characteristics of a hollow core microstructured fiber in the THz regime are numerically investigated. The fiber cladding consists of a triangular lattice formed by a periodic arrangement of dielectric tubes of Teflon. Numerical results show that guidance mechanism is the sameof kagome and square lattice fibers. Low loss and low dispersion frequency ranges can be tuned just by changing the thickness of the tubes irrespectively of their diameter. Propagation loss four decades lower than the bulk absorption and dispersion lower 0.03 ps/(nm km) can be obtained over a band of about 1.7 THz centered at 2.1 THz.

2008 - Fibre a nucleo cavo per applicazioni nella gamma dei THz [Relazione in Atti di Convegno]
Vincetti, Luca; Polemi, Alessia; Zoboli, Maurizio
abstract

In this paper a hollow core photonic band gap fiber is numerically investigated in order to obtain low loss waveguiding in the terahertz region (0.1-10 THz) of the electromagnetic spectrum. Waveguide design in this spectral region is a major challenge due to the high conductivity losses of metals and high absorption of thedielectrics. Numerical results show the eventuality to reach propagation loss two decades lower than the bulk absorption losses of the material used to make the fiber, over a wide range of wavelength.

2008 - Fibre large mode area leakage channel poligonali a dispersione modale ridotta [Relazione in Atti di Convegno]
F., Poli; D., Passaro; A., Cucinotta; S., Selleri; Rosa, Lorenzo; Vincetti, Luca
abstract

In the context of high-power fiber laser applications, effectively single-mode large-mode-area leakage channel fibers employing a single air-hole ring are presented according to a novel design with hole polygonal symmetry around a solid core. Octagonal and decagonal symmetries are studied with attention to penalties arising in bending conditions, aiming for low mode distortion characteristics with respect to hexagonal-lattice fibers.

2008 - Fundamental and high-order mode bending loss in leakage channel fibers [Relazione in Atti di Convegno]
F., Poli; Vincetti, Luca; D., Passaro; A., Cucinotta; S., Selleri; Rosa, Lorenzo; K., Saitoh; Y., Tsuchida; S. K., Varshney; M., Koshiba
abstract

Penalties induced by bending are investigated in large mode area polygonal leakage channel fibers for high-power applications. Fundamental and high-order mode losses are reduced considering decagonal symmetry fibers.

2008 - Ku-Band Radiometer Antenna Characterization in University Test Facilities [Relazione in Atti di Convegno]
Manni, G; Polemi, Alessia; Borgarino, Mattia; Vincetti, Luca
abstract

2008 - Numerical Modeling of S Band EDFA based on Distributed Fiber Loss [Articolo su rivista]
Vincetti, Luca; M., Foroni; F., Poli; Maini, Moreno; A., Cucinotta; S., Selleri; Zoboli, Maurizio
abstract

A numerical model for the analysis and the designof S band erbium-doped fiber amplifiers has been developed. Themodel is able to accurately predict the amplifier performancesby taking into account the ASE suppression due to the bending,as well as leakage losses of the fiber used as active medium.The model has been validated by comparing numerical andexperimental data of bending loss, amplifier gain and noise figureof a S band optical amplifier based on a depressed-claddingerbium-doped fiber. A good agreement has been verified byvarying fiber bending radius, input signal power and wavelength.The model has been then applied to the optimization of theamplifier performances for WDM applications. The numericalresults show that 20 − 25 dB gain can be achieved over a25 − 30nm range centered in different part of the S band from1460nm to 1525nm, just by changing the bending radius andthe length of a depressed-cladding fiber.

2008 - Polygonal Large-Mode-Area Leakage Channel Fibers with Reduced Mode Distortion [Relazione in Atti di Convegno]
Poli, F; Passaro, D; Cucinotta, A; Selleri, S; Vincetti, Luca; Rosa, Lorenzo; Saitoh, K; Tsuchida, Y; VARSHNEY S., K; Koshiba, M.
abstract

2008 - Single-Mode Large-Mode-Area Leakage Channel Fibers with Octagonal Symmetry [Relazione in Atti di Convegno]
Rosa, Lorenzo; Saitoh, K.; Tsuchida, Y.; Varshney, S. K.; Koshiba, M.; Poli, F.; Passaro, D.; Cucinotta, A.; Selleri, S.; Vincetti, Luca
abstract

A novel design for large-mode-area leakage channel fibers with a single ring of air-holes organized with octagonal symmetry has been proposed, obtaining lower bending loss and guided mode distortion with respect to hexagonal symmetry fibers.

2008 - Transponder antenna for SAW sensors [Relazione in Atti di Convegno]
Polemi, Alessia; Vincetti, Luca; Zoboli, Maurizio
abstract

In this paper, the design of an antenna for Radio Transponders (Tag) in wireless systems is presented. In particular, the antenna is part of a sensor unit based on the employment of a Surface Acoustic Wave (SAW) device. The matching between the SAWand the antenna on the Tag is a critical issue of the design, if no matching network are used in order to maintain the costs low. Moreover, the antenna efficiency must be taken under control, and in particular its gain pattern, to guarantee omnidirectionality and to improve the radio activation distances.

2007 - Microstrip Array Antenna for Fire-Detection Applications [Articolo su rivista]
Vincetti, Luca; Polemi, Alessia; Zoboli, Maurizio
abstract

In this paper, a first investigation on critical issues for a fire-detection ground-based Ku-band radiometer antenna design is addressed. A printed technology with standard dielectrics has been employed, to reach low cost, simplicity in realization, and easy integrability with the electronic front-end. The antenna has been designed as an array of patches, where number of elements, spacings, and feeding currents has been optimized to fulfill requirements of low side lobe level and good crosspolarization. For the radio frequency front-end, the receiver architecture is a direct-conversion topology, because it is well suited to be monolithically integrated in a single chip.

2007 - Microstrip Array Antenna for Fire-Detection Applications [Relazione in Atti di Convegno]
Vincetti, Luca; Polemi, Alessia; Zoboli, Maurizio
abstract

Radiometers are widely employed on satellite/aircraft installations for remote sensing of the earth. Furthermore, they have also been recently employed as passive devices which, by measuring the radiation intensity from electromagnetic signals, can detect thermal emissions of real bodies. Thus, passive radiometers operating in the microwave range have started to be used also for fire monitoring and detection.

2007 - Modello numerico di EDFAs per banda S basato su fibre ottiche con cladding depresso [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; Zoboli, Maurizio; M., Foroni; F., Poli; A., Cucinotta; S., Selleri
abstract

A model of a S-band depressed cladding EDFA (Erbium Doped Fiber Amplifier) has been developped. The model is able to predict the ASE suppression due to

2006 - Confinement loss and nonlinearity analysis of air-guiding modified honeycomb photonic bandgap fibers [Articolo su rivista]
Vincetti, Luca; F., Poli; S., Selleri
abstract

Air-guiding photonic bandgap fibers based on a modified honeycomb lattice have been numerically investigated through the finite element method. Results confirm that an extra hole in the unit cell of a honeycomb lattice can be exploited to enlarge the photonic bandgap, allowing air-guiding with confinement losses lower than 0.1 dB/km and nonlinear coefficient lower than 3.5 (.) 10(-3) (W (.) km)(-1) at 1.55 um.

2006 - Fibra a cristallo fotonico con doppio cladding per EDFA operante in banda S [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; Borsari, Gian Paolo; Zoboli, Maurizio
abstract

A compact S-band erbium-doped fiber amplifiers based on a double cladding photonic crystal fiber is presented. ASE suppression in C-band is obtained by mean of leakage loss due to coupling of fundamental mode and outer cladding modes

2006 - Fibre a cristallo fotonico Solid-Core e Air-Guiding: analisi e progetto tramite il metodo degli elementi finiti [Relazione in Atti di Convegno]
Rosa, Lorenzo; M., Foroni; F., Poli; A., Cucinotta; S., Selleri; Maini, Moreno; Vincetti, Luca; Borsari, Gian Paolo; Zoboli, Maurizio
abstract

The finite element method has proved to be a powerful and reliable tool for the analysis and the design of photonic crystal fibers, new and exciting waveguides which can be exploited to enhance proper characteristics of the light for a huge range ofapplications, for example in telecommunications, sensing or biophotonics, unthinkable with standard optical fibers.

2006 - Microstrip Array Antenna Design for a Radiometric Ground-Based Fire Detection Application [Relazione in Atti di Convegno]
Vincetti, Luca; G., Borsari; Maini, Moreno; Polemi, Alessia; Borgarino, Mattia
abstract

In this paper, a first investigation on critical issues for a fire-detection ground-based Ku-band radiometer design is addressed. A printed technology with standard dielectrics has been employed, in order to reach low cost, simplicity in realization and easy integrability with the electronic front-end. The antenna has been designed as an arrays of patches, where number of elements, spacings and feeding currents have been optimized to fulfill requirements of low side lobe level and good crosspolarization.For the radio frequency front-end, the receiver architecture is a direct-conversion topology, because it is well suited to be monolithically integrated in a single chip.

2006 - Modello numerico di EDFAs per banda S basati su fibre ottiche con cladding depresso [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; Zoboli, Maurizio; S., Selleri; A., Cucinotta; F., Poli; M., Foroni
abstract

Viene proposto un modello numerico in grado di prevedere la riduzione o la soppressione della ASE per effetto delle perdite per curvatura.

2006 - Modified Honeycomb Photonic Bandgap Fiber Effectively Single-Mode Regime: A Numerical Analysis [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; Rosa, Lorenzo; Poli, F; Foroni, M; Cucinotta, A; Selleri, S.
abstract

An accurate analysis of the single-mode properties of modified honeycomb photonic bandgap fibers with different geometric characteristics has been carried out by calculating the confinement losses of the fundamental and the higher-order modes. Simulation results have shown that confinement loss lower than 0.1 dB/km and an effectively single-mode behaviour over a wavelength range of about 150 nm can be achieved with a 8 air-hole ring fiber.

2006 - Numerical Analysis of Hollow Core Photonic Band Gap Fibers with Modified Honeycomb Lattice [Relazione in Atti di Convegno]
Gazzetti, C; Maini, Moreno; Vincetti, Luca; Selleri, S; Cucinotta, A; Poli, F.
abstract

Hollow core photonic band gap fibers with a modified honeycomb lattice are investigated by a full vector complex modal solver based on the finite element method. Simulations show that confinement loss lower than 0.1 dB/Km and nonlinear coefficient lower than 5 10-3 (WKm)-1 can be obtained over S, C and L band of the third telecom window.

2006 - Numerical analysis of hollow core photonic band gap fibers with modified honeycomb lattice [Articolo su rivista]
Vincetti, Luca; Maini, Moreno; F., Poli; A., Cucinotta; S., Selleri
abstract

An accurate analysis of the air-guiding in hollow core photonic bandgap fibers with a modified honeycomb air-hole lattice has been carried out. The influence of the hollow core dimension, as well as of the cladding geometric parameters on the confinement loss, the nonlinear coefficient and the single-mode behaviour of the fibers has been investigated through a full-vector modal solver based on the finite element method. Simulation results have shown that confinement loss lower than 0.1 dB/km, a nonlinear parameter lower than 0.01 (W.km)(-1) and an effectively single-mode behaviour over a wavelength range of about 150 nm can be achieved with eight air-hole ring modified honeycomb fibers.

2006 - Numerical Model of a S-band depressed cladding EDFA [Relazione in Atti di Convegno]
S., Selleri; A., Cucinotta; F., Poli; M., Foroni; Maini, Moreno; Vincetti, Luca
abstract

A model of S-band depressed cladding EDFAs (Erbium Doped Fiber Amplifiers) which is able to predict the ASE suppression due to the bending loss has been developed. The comparison of numerical and experimental results has demonstrated the validity of the model.

2005 - Air-guiding photonic crystal fibers with modified honeycomb lattice [Relazione in Atti di Convegno]
Selleri, S; Vincetti, Luca; Poli, F; Cucinotta, A; Foroni, M.
abstract

Air-guiding has been demonstrated in a modified honeycomb photonic crystal fiber. The confinement losses and dispersion properties are numerically investigated by means of the finite element method (FEM). A guided mode with more than 98% of power propagating in air has been found over a wavelength range of about 200 nm. By means of a proper design, confinement losses lower than 0.1 dB/Km at λ = 1.55 μm can be obtained with ten cell rings and an air filling fraction of 74.4%.

2005 - Wide bandgap air-guiding modified honeycomb photonic crystal fibers [Relazione in Atti di Convegno]
Vincetti, Luca; Poli, F; Cucinotta, A; Selleri, S.
abstract

Air-guiding in a photonic crystal fiber with a modified honeycomb lattice has been demonstrated for the first time. A guided mode confined in the hollow core has been found in a wavelength range wider than 200 nm.

2004 - Confinement losses in honeycomb fibers [Articolo su rivista]
Vincetti, Luca
abstract

The confinement losses in honeycomb photonic bandgap fibers are numerically investigated by means of the finite element method. Honeycomb fibers with both an extra hole and a low refractive index region as defects are considered. It is shown that by means of a proper design, confinement losses lower than 0.1 dB/km at λ=1.55 μm can be obtained with four hole rings.

2003 - Amplification properties of Er3+-doped photonic crystal fibers [Articolo su rivista]
A., Cucinotta; F., Poli; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

The amplification properties of different photonic crystal fibers have been studied by means of a full vector finite-element modal formulation combined. with a population and propagation. rate equation solver. A honeycomb as well as a cobweb photonic crystal fiber have been considered. The consequences of the defect dimension and the dopant radius on the field intensity distribution as well as the. overlap integrals have been analyzed. Results demonstrate that a proper photonic crystal fiber design can be usefully exploited in order to obtain active fibers with superior characteristics. compared to standard step index ones. In particular, photonic crystal fibers open no the possibility of a gain medium with highly flexible geometric, dispersion, and amplifying characteristics.

2003 - Characterization of microstructured optical fibers for wideband dispersion compensation [Articolo su rivista]
F., Poli; A., Cucinotta; S., Selleri; M., Fuochi; Vincetti, Luca
abstract

Microstructured optical fibers (MOFs) with small hole-to-hole spacing and large airholes are designed to compensate the anomalous dispersion and the dispersion slope of single-mode fibers. The geometrical parameters that characterize triangular MOFs are chosen to optimize the fiber length and the compensation over a wide wavelength range. A proper design of the photonic crystal fiber geometry allows us to achieve dispersion values of approximately -1700 ps nm(-1) km(-1) at 1550 nm and to compensate the dispersion of standard fibers within +/-0.5 ps nm(-1) km(-1) over a 100-nm range. The MOF dispersion properties have been studied by means of a numerical simulator for modal analysis based on the finite-element method.

2003 - Comparison of the Jones Matrix Analytical Models Applied to Optical System Affected by High-Order PMD [Articolo su rivista]
A., Orlandini; Vincetti, Luca
abstract

Abstract—The analytical models for the Jones matrix of anoptical fiber affected by high-order polarization-mode dispersion(PMD) are studied in an original comparative analysis with thepurpose of finding a useful, precise, and stable tool for the systemperformance evaluation. First, a preliminary deterministic studyis done to explain how the conceptual difference among the modelsreflects onto their representation of the fiber PMD effects interms of Jones matrix coefficients and dispersion vector. Then, theanalytical models with PMD up to third order are exploited forthe calculation of the outage probability on the sensitivity penaltyat the receiver, and the results obtained are compared with thoseof the discrete random wave-plate numerical model, assumed as afaithful description of the real fiber. Two different approaches areused for the outage probability evaluation: an analytical method,which is precise and faster but can only be used with PMDparameters up to second order, and a semi-analytical methodthat allows a comparison of the numerical and analytical resultswith homogeneity, when the statistics of high-order PMD arenot known. The analytical model, which describes the dispersionvector as rotating on a circumference in the Stokes space, is foundto be the most accurate in the system performance computation.

2003 - Dispersion and Non-Linear Properties of Triangular Photonic Crystal Fibers with Large Air-Hole and Small Pitch [Relazione in Atti di Convegno]
F., Poli; A., Cucinotta; M., Fuochi; S., Selleri; Vincetti, Luca
abstract

Triangualr PCFs with large air-holes and a small pitch are successfully designed through the finite element method in order to compensate the signal dispersion over wide bandwidths and to enhance fiber non-linearity

2003 - Finite Element analysis of Optical Notch Filters Based on Photonic Crystals [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; M., Zoboli
abstract

A photonic crystal based notch filter is analyzed by means of Finite element Method. Simulation results show that the filter exhibits a a notch with very narrow bandwidth and its position can be easily tuned with high accuracyover a wide range of wavelengths.

2003 - Leakage Losses in Photonic Band Gap Fibers [Relazione in Atti di Convegno]
Vincetti, Luca; D., Ferrarini; A., Cucinotta; F., Poli; S., Selleri
abstract

Leakage losses are investigated in fibers where the guididng is based on photonic band gap. This kind of fibers exhibits higher losses and lower sensitivity to holes number than fibers based on total internal reflection.

2003 - Leakage Losses in Photonic Crystal Fibers [Relazione in Atti di Convegno]
D., Ferrarini; Vincetti, Luca; Zoboli, Maurizio; A., Cucinotta; F., Poli; S., Selleri
abstract

The reduction of leakage losses is a key issue for PCF optical applications. The finite elements provide a powerful tool for low loss fiber design and foresee losses of the same order of standard fibers.

2003 - Overview on finite-element time-domain approaches for optical propagation analysis [Articolo su rivista]
A., Bertolani; A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Several finite-element based time-domain approaches for the analysis of photonic devices are discussed in details. Narrowband and different kinds of wideband formulations are derived highlighting strengths and weaknesses related to the initial analytical equation and to the numerical implementation through the finite element method. A formulation which directly implements the unknown field without separating the envelope and the fast varying carrier is also presented. Performances and limits of the various algorithms are discussed by analyzing the simple and clear case of time and space evolution of gaussian beams propagating in a homogeneous medium. Comparison of the modules and arguments of the spectral response is also provided.

2003 - Raman Amplification Properties of Silica and Tellurite Photonic Crystal Fibers [Relazione in Atti di Convegno]
M., Fuochi; F., Poli; A., Cucinotta; S., Selleri; Vincetti, Luca
abstract

Raman properties of silica and tellurite photonic crystal fibers are investigated and compared. A significant increase in Raman gain coefficient is possible by tailoring the triangular lattice holes.

2003 - Study of Raman amplification properties in triangular photonic crystal fibers [Articolo su rivista]
M., Fuochi; F., Poli; S., Selleri; A., Cucinotta; Vincetti, Luca
abstract

In this paper, the Raman properties of triangular photonic crystal fibers (PCFs) are analyzed in order to design a fiber for Raman amplification with enhanced performances. By casting the Raman intensity propagation equations, the Raman effective area and the Raman gain coefficient are introduced-two meaningful parameters that take into account the overlap between the pump and signal profiles. The behavior of these two parameters is examined in silica PCFs as a function of the geometrical characteristics of the triangular lattice. The numerical results show that a proper design of the hole diameter and the spacing between air holes can minimize the Raman effective area and maximize the Raman gain coefficient. The paper then focuses on the PCFs with germania-doped core. It is found that, for a given PCF cross section and dimension of the doped region, the Raman gain coefficient increases linearly with the germania concentration. Moreover, by enlarging the doped region, it is discovered that a PCF with a germania-doped area internally tangent to the first ring of air holes has a maximum Raman gain coefficient. Finally, the calculated values of the Raman gain coefficient are compared with those of other highly nonlinear fibers presented in literature, showing that a well-designed triangular PCF can significatively improve the Raman gain performances.

2002 - Amplification Properties of Erbium Doped Photonic Crystal Fibers [Relazione in Atti di Convegno]
S., Selleri; A., Cucinotta; F., Poli; Vincetti, Luca; Zoboli, Maurizio
abstract

Photonic crystals can be used in order to efficiently exploit amplification properties of doped optical fibers. The mode areas for pump and signals can be easily controlled, in particular reduced with respect to standard step index fibers, giving rise to a gain improvement of more than 10 dB for a fixed dopant concentration.

2002 - Analisi delle Proprietà di Amplificazione di Fibre a Cristallo Fotonico Drogate con Erbio [Relazione in Atti di Convegno]
A., Cucinotta; F., Poli; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

2002 - Holey fiber analysis through the finite-element method [Articolo su rivista]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A holey fiber (HF), having very complex hole geometry, is studied by means of a numerical simulator for modal analysis based on the finite-element method (FEM). Polarization and dispersion properties as well as the full vector field distribution of the fundamental mode are investigated. The obtained numerical results show a good agreement with experimental ones reported in literature.

2002 - Leakage properties of photonic crystal fibers [Articolo su rivista]
D., Ferrarini; Vincetti, Luca; Zoboli, Maurizio; A., Cucinotta; S., Selleri
abstract

An analysis of the confinement losses in photonic crystal fibers due to the finite numbers of air holes is performed by means of the finite element method. The high flexibility of the numerical method allows to consider fibers with regular lattices, like the triangular and the honeycomb ones, and circular holes, but also fibers with more complicated cross sections like the cobweb fiber. Numerical results show that by increasing the number of air hole rings the attenuation constant decreases. This dependence is very strong for triangular and cobweb fibers, whereas it is very weak for the honeycomb one.

2002 - Mesh Truncation in Finite Element Modal Analysis of Dielectric Waveguides [Articolo su rivista]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Anisotropic layers with real permittivity and permeability tensors are used to enclosethe computational domain for vectorial modal analysis of dielectric waveguidesthrough the finite element method. The approach does not require any iterative procedure.It is computationally efficient and reliable, it can directly calculate many modesat the same time, and it is very accurate in providing both the vectorial field distributionand the propagation constant. Analysis of performances is provided for differentdielectric waveguides by varying the constituent parameters of the layers.

2002 - Perturbation analysis of dispersion properties in photonic crystal fibers through the finite element method [Articolo su rivista]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Perturbations to the ideal cross section of photonic crystal fibers (PCFs) are introduced in order to investigate their performances as a function of the structural fluctuations which may occur during fabrication. The effects of the cross-section geometry perturbations on the dispersion characteristics like dispersion parameter and differential group delay are presented and discussed. The analysis has been performed through the finite element method, which assures high flexibility and high solution accuracy.

2002 - Photonic Crystal Fibers: Perturbation Analysis of Polarization and Dispersion Properties [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Dispersion properties of photonic crystal fibers are analyzed by introducing perturbations to the ideal cross-section geometry in order to investigate their performances as a function of the structural fluctuations which may occur during fabrication. Results and effects related to the variation of the dispersion parameter and the differential group delay are presented and discussed.

2002 - Studio di un Filtro Notch a Cristallo Fotonico Mediante il Metodo degli Elementi Finiti [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A photonic crystal based notch filter is analyzed by mean of Finite element Method both in time and in frequency domain. simulation results show that the filter exhibits a notch with very narrow bandwidth and its position can be easily tuned with high accuracy over a wide range of wavelengths

2002 - Truncation of finite-element mesh for modal analysis of dielectric waveguides [Articolo su rivista]
S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A new approach,for mesh truncation in the finite-element vectorial modal analysis of dielectric waveguides is presented. It is based on layers with real anisotropic permittivity and permeability tensors. The approach does not require any iterative procedure, can directly calculate many modes at the same time, and is very accurate in providing both the vectorial field distribution and the propagation Constant. The resulting matrices for the eigenvalue problem are still sparse and real, thus limiting the computational effort. Mode cutoff conditions can be easily studied with high precision.

2001 - A Simple and Useful Model for Jones Matrix to Evaluate Higher Order Polarization Mode Dispersion Effects [Articolo su rivista]
A., Orlandini; Vincetti, Luca
abstract

Starting from the differential equation that relatesthe Jones matrix of a polarization-mode dipersion (PMD) fiber toits output dispersion vector, the analytical expressions of the matrixcoefficients are determined in the case of a dispersion vectorrotating on a circonference in the Stokes space. This model, thatneeds only few parameters with known statistics, is applied to evaluatethe performance of an optical system. The results obtainedwith it and with other models proposed in literature are comparedto those evaluated by numerical simulations with all-order PMDeffects, showing that our model gives an accurate representation ofreal system performances.

2001 - Analytical evaluation of optical system impairments caused by high-order polarization-mode dispersion effects [Articolo su rivista]
A., Orlandini; Vincetti, Luca
abstract

The differential equation that relates the Jones matrix of a polarization-mode dispersion fiber to its output dispersion vector is solved for a dispersion vector that moves on a circumference in the Stokes space, It yields a new simple model that can be usefully exploited to calculate the pulse-broadening analytical expression and to evaluate the system performance in terms of outage probability. A comparison among the results obtained with it, with other models proposed in literature, and with the numerical DRW model show its best accuracy.

2001 - Caratterizzazione di Vetri Tellurati per Amplificatori Ottici in Banda L [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca
abstract

2001 - Comparative Study among Analytical and Nomerical Models for the Performance Evaluation of Optical Systems Affected by Polarization Mode Dispersion [Relazione in Atti di Convegno]
A., Orlandini; Vincetti, Luca; E., Forestieri
abstract

In the present work the analytical models are applied to calculate the system performance for different fibre polarisation mode dispersion (PMD) conditions and for varying system parameters and the results obtained with them are compared to those obtained using the discrete random waveplate numerical model (DRW) model, assumed as a faithful description of the real fiber with all order PMD effects. Through this comparative analysis, never done before in literature to the authors knowledge, the accuracy of the analytical models in the approximation of high-order PMD effects is studied, and, among them, a precise analytical tool for the system impairments evaluation is found.

2001 - Comparison among first order PMD compensation techniques [Relazione in Atti di Convegno]
Orlandini, A.; Vincetti, L.; Fiorone, R.
abstract

A comparision among three different first order polarization mode dispersion compensation techniques was done in terms of outage probability. This probability was calculated for a fixed value of sensitivity penalty at the reciever with the purpose of evaluating their impact on 10 Gbit/s communication system performance for different conditions of polarization mode dispersion and for varying compensation parameters. A numerical approach was applied looking for the best operating point of compensation © 2001 SPIE · 0277-786X/01/$15.00.

2001 - Complex FEM modal solver of optical waveguides with PML boundary conditions [Articolo su rivista]
S., Selleri; Vincetti, Luca; A., Cucinotta; Zoboli, Maurizio
abstract

A full-wave modal analysis of two-dimensional, lossy and anisotropic optical waveguides using the finite element method (FEM) is presented. In order to describe the behavior of radiating fields, anisotropic perfectly matched layer boundary conditions are applied for the first time in modal solvers. The approach has been implemented using high order edge elements. The resulting sparse eigenvalue algebraic problem is solved through the Arnoldi method. Application to an antiresonant reflecting optical waveguide is reported.

2001 - Exact Evaluation of the Jones Matrix of a Fiber in the Presence of Polarization Mode Dispersion of Any Order [Articolo su rivista]
E., Forestieri; Vincetti, Luca
abstract

This paper describes how to evaluate exactly in arecursive manner the Jones transfer matrix of a fiber for anyorder of polarization mode dispersion (PMD) and derives for ita second-order accurate analytical approximation. The secondorderapproximation is then compared against the exact result aswell as with other models found in the literature.

2001 - Impact of the cell geometry on the spectral properties of photonic crystal structures [Articolo su rivista]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Photonic-crystal-based devices are expected to perform many of the functionalities of standard integrated optics devices used in optical communication systems. Their reliability and the reliability of fabrication technologies in achieving acceptable geometrical tolerance are still to be demonstrated. In this work an analysis of the effects of the cell geometry is presented, showing how small variations can cause hundreds of GHz shifts in the spectral response. A wide-band, finite-element time-domain approach and a frequency-domain formulation have been used for this kind of analysis. The ability of the finite-element method in coping with any kind of geometry has been successfully exploited to investigate the effect of the cell shape.

2001 - Photonic Crystals: Analysis and Design Approaches Based on the Finite Element Method [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

To investigate light propagation in photonic crystal structures, the finite element method is employed starting from different analytical formulations, both in time and harmonic regime. Application to integrated waveguides and optical fibers are presented.

2000 - Analisi numerica di guide magneto-ottiche [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

2000 - Anisotropic and Magnetooptic Waveguide Numerical Analysis [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Anisotropic and magnetooptics waveguides have important applications as integrated optics polarization dependent devices.Their functionalities and performances are analysed by means of ananisotropic finite element full vectorial beam propagation method.The polarization dependence and the coupling due to both the material and the geometric effects are considered.

2000 - Comparison among First Order PMD Compensator Techniques [Relazione in Atti di Convegno]
A., Orlandini; Vincetti, Luca; R., Fiorone
abstract

Three different first order polarization mode dispersion compensation techniques are compared in terms of outage probability, calculated for a fixed value of sensitivity penalty at the receiver, with the purpose of evaluating their impact on 10 Gbit/s communication system performance. A numerical approach is followed for different conditions of polarization mode dispersion and for varying compensation parameters, looking for the best operating point of compensation.

2000 - Full-vector finite-element beam propagation method for anisotropic optical device analysis [Articolo su rivista]
S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A finite-element full-vectorial beam-propagation method is presented,for the first time, for the analysis of 3-D anisotropic optical waveguides, Full 3 x 3 permittivity and permeability tensors are considered. The formulation takes into account the polarization dependence and the component coupling due to the waveguide geometry and the medium anisotropy without any analytical approximations. The perfectly matched anisotropic absorber is introduced to eliminate the influence of the computational border on the numerical solutions. The correctness of the proposed approach is verified by analyzing several kinds of anisotropies. For the first time, a full vectorial finite-element propagation analysis is presented for diffuse waveguides and magnetooptic devices.

2000 - Jones Transfer Matrix for Polarization Mode Dispersion Fibers [Relazione in Atti di Convegno]
A., Orlandini; Vincetti, Luca
abstract

With the advent of long distance high bit rate optical systems, polarization mode dispersion (PMD) has become an important source of limitation for the system performance. In a first order approximation, PMD, that is described by a differential group delay (DGD) between two orthogonal states of polarization (PSPs), causes an undesired output pulse broadening; the frequency dependence of DGD and PSPs produces other distorting effects, considered as higher order PMD effects. A useful theoretical means of predicting the overall distortion of the transmitted signal is the evaluation of the Jones transfer matrix of the fiber but, unfortunately, the statistics of its coefficients are not available up to now. On the other hand, the statistical behavior of the three-dimensional dispersion vector, that characterizes the PMD of the fiber in the Stokes space and can be measured, is known up to a second order PMD approximation. Consequently, finding the analytical relationship between the PMD vector and the coefficients of the Jones matrix is mandatory. In the work, the tight methodology of calculating the Jones matrix, starting from the knowledge of the PMD vector, is shown. This new method is used to determine the output temporal pulse expression in a second order PMD approximation and it is applied to evaluate the performance of a system affected by PMD. The results obtained with the present model are compared to the performance evaluated by numerical simulations, where all order PMD effects are taken into account; our model gives a performance curve that is more accurate in the approximation of all order PMD effects

2000 - Open Waveguide Boundary Conditins for Finite Element Analysis [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Mesh truncation in finite element vectorial modal analysis of dielectric waveguides is performed by means of layers with anisotropic permittivity and permeability tensors. The approach is very accurate, does not require iterative procedures, directly calculates many modes at the same time. The resulting matrices for the eigenvalue problem are still sparse and real.

2000 - Open Waveguide Boundary Conditions for Finite Element Modal Analysis [Relazione in Atti di Convegno]
Cucinotta, A.; Selleri, S.; Vincetti, L.; Zoboli, M.
abstract

Mesh truncation in finite element vectorial modal analysis of dielectric waveguides is performed by means of layers with anisotropic permittivity and permeability tensors. The approach is very accurate, does not require iterative procedures, directly calculates many modes at the same time. The resulting matrices for the eigenvalue problem are still sparse and real.

2000 - Three-dimensional finite-element beam propagation method: Assessments and developments [Articolo su rivista]
VINCETTI, Luca; A., Cucinotta; S., Selleri; ZOBOLI, Maurizio
abstract

In recent years the finite-element method (FEM) has been widely applied to three-dimensional beam propagation analysis, and several FEM propagators have been presented. Up to now, as far as we know, an exhaustive, deep, and comparative analysis of these formulations and of the related algorithms has never been presented. We critically analyze and numerically compare, to our knowledge for the first time, different vectorial, semivectorial, and scalar formulations in order to check their performances, point out weaknesses, and suggest future developments. The results obtained highlight once more the inadequacy of scalar approaches in dealing with actual photonics devices and suggest vector formulations worthy of further development and future research.

1999 - Active Nonlinear Integrated Optical Devices: a Numerical Analysis [Articolo su rivista]
Cucinotta, ; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A finite element beam propagation method to analyze nonlinear active optical waveguides ispresented. The model takes into account the mutual coupling among the equations describing the elec-tromagnetic field propagation and the ones governing the signal amplification due to a doped medium.The approach is able to distinguish the different behavior of Ex (quasi-TE) and Ey (quasi-TM) polariza-tions. The performances of nonlinear and doped couplers are analyzed in detail by varying the inputpower, the field polarization and the pumping scheme.

1999 - Nonlinear Finite-Element Semivectorial Propagation Method for Three-Dimensional Optical Waveguides [Articolo su rivista]
A., Cucinotta; S., Selleri; Vincetti, Luca
abstract

A nonlinear semivectorial beam propagation methodbased on the finite element method is presented. It applies tothree-dimensional optical waveguides and accounts for polarizationeffects. To show the usefulness of this approach numericalresults regarding both Ex (quasi-TE) and Ey (quasi-TM) wavesare presented for directional couplers with nonlinear cores. Thelimits of scalar formulations are highlighted especially whenworking near and above the coupler threshold power.

1999 - Perfectly Matched Anisotropic Layers for Optical Waveguides Analysis through the Finite Element Beam Propagation Method [Articolo su rivista]
Cucinotta, ; G., Pelosi; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

Perfectly matched anisotropic absorbers are introduced in two- and three-dimensional beam propagation methods. The anisotropic perfectly matched layer does not require the modification of Maxwell's equations, and can be easily implemented in codes which deal with anisotropic materials. Finite-element semivectorial and full-vectorial formulations have been considered to prove the efficiency of the proposed approach.

1998 - Finite Element Method Resolution of Non-Linear Helmholtz equation [Articolo su rivista]
S., Selleri; Vincetti, Luca; A., Cucinotta
abstract

A non-paraxial beam propagation method for non-linear media is presented. It directlyimplements the non-linear Helmholtz equation without introducing the slowing varyingenvelope approximation. The finite element method has been used to describe the fieldand the medium characteristics on the transverse cross-section as well as along thelongitudinal direction. The finite element capabilities as, for example, the non-uniformmesh distribution, the use of adaptive mesh techniques and the high sparsity of thesystem matrices, allow one to obtain a fast, versatile and accurate tool for beampropagation analysis. Examples of spatial soliton evolution describe phenomena notpredicted in the frame of the slowing varying envelope approximation.

1998 - Finite-element full-vectorial propagation analysis for three dimensional z-varying optical waveguides [Articolo su rivista]
E., Montanari; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A finite-element-based full-vectorial beam propagationmethod (BPM) for the analysis of the electromagneticfield evolution in three-dimensional (3-D) dielectric waveguides ispresented. The approach has been derived in order to be suitablefor the numerical discretization through finite elements and tofully account for the vectorial nature of the electromagnetic field.To this aim the problem related to the permittivity derivativeat dielectric interface has been addressed and overcome. Theadvantages and the potentialities of the finite elements usageare discussed. The precision and the correctness of the proposedapproach is demonstrated through numerical examples. Typicalintegrated optics structures, as a tapered waveguide and a Y -junction, are analyzed to assess the applicability of the method.

1998 - Finite-Element semivectorial Beam Propagation Method for Nonlinear Integrated Optical Devices [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca
abstract

A semivectorial beam propagation method based on finite elements for nonlinear waveguides is presented. Due to its semivectorial nature the approach accounts for polarization effects and highlights the limits of scalar formulations.

1998 - Finite-elements semivectorial beam propagation method for nonlinear integrated optical devices [Relazione in Atti di Convegno]
Cucinotta, A.; Sellen, S.; Vincetti, L.
abstract

1998 - Nonlinear Heimholtz equation resolution through the finite element method [Relazione in Atti di Convegno]
Cucinotta, A.; Selleri, S.; Vincetti, L.
abstract

1998 - Nonlinear Helmholtz Equation Resolution through the Finite Element Method [Relazione in Atti di Convegno]
A., Cucinotta; S., Selleri; Vincetti, Luca
abstract

A fast and accurate full-FEM-based propagation method that directly implement the nonlinear Helmholtz equation is presented.The analysis of spatial soliton evolution confirms phenomena not described in the frame of the slowing varying envelope approximation.

1998 - Numerical and Experimental Analysis of Erbium Doped Fiber Linear Cavity Laser [Articolo su rivista]
Cucinotta, ; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A numerical and experimental analysis of an erbium-doped linear cavity laser is presented. In particular a numericalmodel for the laser continuous wave and multiwavelength operation has been developed. In the proposed approach,according to the spectral model, the propagation rate equations have been used to predict the evolution of forward andbackward signals and amplified spontaneous emission in the doped waveguide and properly boundary conditions have beenimposed to describe the resonant etalon. The performances of the erbium-doped linear cavity laser are investigated in detailand the best parameters to optimize the laser design as, for example, the mirror or grating reflectivities, the cavity length andthe pump power are investigated. Comparisons with experimental data confirm the validity of the approach. Numericalresults point out the model usefulness for device design.

1997 - Finite-Element Formulation for Full-Vectorial Propagation Analysis in Three-Dimensional Optical Waveguides [Articolo su rivista]
E., Montanari; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

A three-dimensional (3-D) full-vectorial beam propagationmethod based on finite elements is presented. A newformulation suitable for the numerical discretization through thefinite elements and able to take into account both polarizationdependence and field component coupling has been derived.Advantages and potentialities of the finite elements usage are discussed.The precision of the proposed approach is demonstratedthrough numerical examples.

1997 - Finite-Element Full-Vectorial Propagation Analysis for Three Dimensional Anisotropic Waveguides [Relazione in Atti di Convegno]
A., Cucinotta; E., Montanari; S., Selleri; Vincetti, Luca; Zoboli, Maurizio
abstract

The Beam Propagation Method (BPM) has been extensivelyemployed to study the properties of various guided wave optic structures such as optical fibers and integrated optical waveguides.In these photonic devices anisotropic materials are often used as guiding media so that full vectorial BPMs result mandatory in order to perform a reliable electromagnetic analysis.In this work, for the first time to author's knowledge, a full-vectorial beam propagation method based on the Finite Elements (FE-VBPM) has been developed for three dimensional optical waveguides with anisotropic materials.