Showing papers by "Giuseppe Coppola published in 2020"

Roadmap on holography

Abstract: This work was supported by Ministerio de Economia, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015.

Polarization-Sensitive Digital Holographic Imaging for Characterization of Microscopic Samples: Recent Advances and Perspectives

Abstract: Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very fast and does not require labels/markers, it finds application in several fields, from biology to microelectronics and micro-photonics. In this paper, a comprehensive review of the state-of-the-art of PS-DHI techniques, the theoretical principles, and important applications are reported.

Integrated Er/Si Schottky Photodetectors on the end facet of optical waveguides

Abstract: In the last two decades there has been growing interest in silicon photonics and in the possibility to integrate new materials to overcome the silicon intrinsic limitations. Erbium has represented a viable solution for the realization of light sources at telecommunications wavelengths opening the path to the investigation of various photonic devices based on rare earth. In this work we investigate a photodetector operating at 1550 nm whose detection mechanism is based on the internal photoemission effect through an Er/Si Schottky junction. The Er/Si junction has been carefully electrically characterized showing a potential barrier and cut-off wavelength of 0.59 eV and 2105 nm, respectively. Moreover, a responsivity of 0.62 mA/W has been measured for a 3 μm-width waveguide at 1550 nm and at reverse voltage of -8 V. Finally, the noise equivalent power of the device has been evaluated as high as 0.53 nW/(Hz)1/2 at -8 V. Even if device responsivity is still low, we believe that our insights may suggest Er/Si as a new platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.

Silicon Meet Graphene for a New Family of Near-Infrared Resonant Cavity Enhanced Photodetectors

Abstract: In this work we have investigated resonant cavity enhanced (RCE) photodetectors (PDs), exploiting the Internal Photoemission Effect (IPE) through a Single Layer Graphene (SLG) replacing metals in the Silicon (Si) Schottky junctions, operating at 1550 nm. The SLG/Si Schottky junction is incorporated into a Fabry-Perot (F-P) optical microcavity in order to enhance both the graphene absorption and the responsivity. These devices are provided of high spectral selectivity at the resonance wavelength which can be suitably tuned by changing the length of the cavity. We get a wavelength-dependent photoresponse with external responsivity ∼20 mA/W in a planar F-P microcavity with finesse of 5.4. In addition, in order to increase the finesse of the cavity, and consequently its responsivity, a new device where the SLG has placed in the middle of a Si-based F-P microcavity has been proposed and theoretically investigated. We have demonstrated that, in a properly designed device, a SLG optical absorption, responsivity and finesse of 100%, 0.43 A/W and 172 can be obtained, respectively. Unfortunately, the estimated bandwidth is low due to the planarity of the structure where both Ohmic (AI) and Schottky (SLG) contacts are placed in the same plane. In order to improve the PD bandwidth, we have fabricated and characterized a prototype of a vertical RCE SLG/Si Schottky PD where two contacts are both placed at the edges of a high-finesse 200nm-thick Si-based microcavity. Thanks to this innovative structure an increase of the responsivity-bandwidth product is expected. The insights included in this work can open the path for developing of a new family of high-performance photodetectors that can find application in silicon photonics.

Bound-state in the continuum of a photonic crystal metasurface: a platform for ultrasensitive sensing and near field amplification

Abstract: The localization of the electromagnetic field at the nanoscale can play a key role in many applications, such as sensing, spectroscopy and energy conversion. In the last years, great efforts have been performed to study and realize all-dielectric loss-free nanostructures to confine the radiation without the limits imposed by the plasmonic systems. Here we demonstrate that the field enhancement in proximity of a photonic crystal metasurface supporting bound states in the continuum can be explored to boost the light-matter interaction. We design and realize an innovative sensing scheme for bulk and surface measurement with ultra-high figure of merit and apply this new configuration for studying a specific protein-protein interaction. The recognition scheme can be coupled to a fluorescence-based sensing approach, which exploits the capability of the sensor to strongly enhance fluorescence signals. Our results provide new solutions for light manipulation at the nanoscale, especially for sensing and nonlinear optics applications.

A Polarized Digital Holographic Approach in Biological and Medical Research

Abstract: A new, simple digital holography-based polarization microscope for birefringence imaging of biological cells is presented. This approach could open the way to a new class of label-free diagnostic tool in biological and medical research and diagnosis.

Volume Phase Holographic Lenses for Efficient Planar Solar Track-Concentrators

Abstract: Volume transmission phase holographic lenses were designed and recorded to obtain a simple, lightweight, compact and inexpensive planar solar concentrator. To avoid any mechanical movement, a passive solar tracking system is also proposed by using angular multiplexed holographic lenses. Furthermore, these solar concentrators have no overheating problems resulting from the absorption of infrared frequencies, because in this spectral region the proposed volume holographic lenses do not work. Finally, the realized samples were tested and a good efficiency was obtained.