Showing papers by "Giuseppe Coppola published in 2017"

Vertically Illuminated, Resonant Cavity Enhanced, Graphene–Silicon Schottky Photodetectors

Abstract: We report vertically illuminated, resonant cavity enhanced, graphene–Si Schottky photodetectors (PDs) operating at 1550 nm. These exploit internal photoemission at the graphene–Si interface. To obtain spectral selectivity and enhance responsivity, the PDs are integrated with an optical cavity, resulting in multiple reflections at resonance, and enhanced absorption in graphene. We get a wavelength-dependent photoresponse with external (internal) responsivity ∼20 mA/W (0.25A/W). The spectral selectivity may be further tuned by varying the cavity resonant wavelength. Our devices pave the way for developing high responsivity hybrid graphene–Si free-space illuminated PDs for optical communications, coherence optical tomography, and light-radars.

PDMS membranes as sensing element in optical sensors for gas detection in water

Abstract: Polydimethylsiloxane (PDMS) has been introduced the first time about 20 years ago. This polymer is worldwide used for the rapid prototyping of microfluidic device through a replica molding process. However, the great popularity of PDMS is not only related to its easy processability, but also to its chemical and physical properties. For its interesting properties, the polymer has been implied for several applications, including sensing. In this work, we investigated how to use functionalized PDMS membranes as sensing elements in optical sensors for gas detection in water samples.

Microfluidic technology for cell hydrodynamic manipulation

Abstract: In the recent years microfluidic technology has affirmed itself as a powerful tool in medical and biological research. Among the different applications, cell manipulation has been widely investigated. Micro-flowcytometers, micromixers, cell sorters and analyzers are only few examples of the developed devices. Various methods for cell manipulation have been proposed, such as hydrodynamic, magnetic, optical, mechanical, and electrical, in this way categorized according to the manipulating force employed. In particular, when cells are manipulated by hydrodynamic effects, there is no needing of applying external forces. This brings to a simplification in the design and fabrication phase, and at the same time undesired effects on the biological sample are limited. In this paper, we will discuss the physics of the relevant hydrodynamic effects in microfluidics, and how they are exploited for cell manipulation.

Volume Holographic Optical Elements as Solar Concentrators

Abstract: In this chapter, we investigate the possibility to realize a holographic solar concentrator by using a new photopolymeric material as recording medium. Therefore, two different configurations of holographic lenses (lenses with spherical and cylindrical symmetry) are described in terms of both recording process and optical response characterization. Finally, we propose the possibility to use this new photopolymer to realize holographic solar concentrator for space applications.

Optical sensors based on photonic crystal: a new route

Abstract: The realization of miniaturized devices able to accumulate a higher number of information in a smallest volume is a challenge of the technological development This trend increases the request of high sensitivity and selectivity sensors which can be integrated in microsystems In this landscape, optical sensors based on photonic crystal technology can be an appealing solution Here, a new refractive index sensor device, based on the bound states in the continuum (BIC) resonance shift excited in a photonic crystal membrane, is presented A microfluidic cell was used to control the injection of fluids with different refractive indices over the photonic crystal surface The shift of very high Q-factor resonances excited into the photonic crystal open cavity was monitored as a function of the refractive index n of the test liquid The excellent stability we found and the minimal, loss-free optical equipment requirement, provide a new route for achieving high performance in sensing applications

EIT-like all-dielectric metamaterials with phase changing layers for all-optical switching applications

Abstract: In this work, we propose the hybridization of all-dielectric metasurfaces based on Si nanoresonators with thin layers of phase change materials (PCM). The concept of all-dielectric metasurfaces is important when one needs to avoid inherent ohmic losses in metal-based nanostructures, e.g. for high Qfactor and figure of merit (FOM). Si nanoresonators can possess electric and magnetic resonances while having low losses in the desired range. On the other hand, chalcogenide PCM have at least two phases with different optical properties, stable at room temperature; switching between these two phases can be reversibly done by a visible laser. If a thin PCM layer is put in contact with Si nanoresonator, its phase-change will change the dielectric environment of the nanoresonator, thus changing the overall resonant response. We numerically investigate the all-optical switching in telecom range of the metasurface based on nanorods and square-like nanorings, namely “bright” and “dark” nanoresonators, respectively. We then experimentally report on the PCM switching metasurface based on nanorods, i.e. “bright” resonators. We strongly believe that this research could lead to new perspectives in all-optical, all-dielectric nanophotonics.

Advanced Label-Free Optical Methods for Spermatozoa Quality Assessment and Selection

Abstract: Current in vitro fertilization (IVF) techniques require a severe selection of sperm, generally based on concentration, morphology, motility, and DNA integrity. Since routinely separation methods may damage the viability of the sperm cell, there is a growing interest in providing a method for noninvasively analyzing spermatozoa taking into account all those parameters. This chapter first reviews the state-of-the-art of label-free sperm cell imaging for IVF, highlighting the limitations of the used techniques. Then, our innovative approach combining Raman spectroscopy and digital holography will be described and its advantages detailed. These include the ability to perform a simultaneous and correlative morphological and biochemical analysis of sperm cells, without labeling, in a fast and reliable way. Finally, the difficulty in reaching clinical use will be discussed, as well as the possible solutions offered by new technological improvements.

Unlabeled Semen Analysis by Means of the Holographic Imaging

Abstract: The morphology, the motility, and the biochemical structure of the spermatozoon have often been correlated with the outcome of in vitro fertilization and have been shown to be the sole parameters of the semen analysis in predicting the success of intracytoplasmic sperm injection and intracytoplasmic morphologically selected sperm injection. In this context, digital holography has demonstrated to be an attractive technique to perform a label-free, noninvasive, and high-resolution technique for characterization of live spermatozoa. The aim of this chapter is to summarize the recent achievements of digital holography in order to show its high potentiality as an efficient method for healthy and fertile sperm cell selection, without injuring the specimen and to explore new possible applications of digital holography in this field.

Introduction to the Issue on Reports From the Invited and Postdeadline Speakers of CLEO 2016

Abstract: The papers from this special section were presented at the CLEO 2016 Conference. The purpose of this issue is to highlight the high impact work from the conference related to Science and Innovations and Fundamental Science/QELS. The papers in this issue highlight the latest leading-edge developments in silicon photonics, fiber and semiconductor lasers, fiber communications, metamaterials, laser material processing, bio-photonics, and ultrafast optical science and technology.