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FEDERICO MELLI

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Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Azimuthal Fourier decomposition for loss analysis of hollow-core tube lattice fibers part I: Ideal fibers [Articolo su rivista]
Melli, F.; Vasko, K.; Rosa, L.; Benabid, F.; Vincetti, L.
abstract

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.

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 - 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 - 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 - 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

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.

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.

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.