Giuseppe Coppola

Bio: Giuseppe Coppola is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 40, co-authored 256 publications receiving 5489 citations. Previous affiliations of Giuseppe Coppola include Seconda Università degli Studi di Napoli & University of Naples Federico II.

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.

Optical properties of diatom nanostructured biosilica in Arachnoidiscus sp: micro-optics from mother nature.

Abstract: Some natural structures show three-dimensional morphologies on the micro- and nano- scale, characterized by levels of symmetry and complexity well far beyond those fabricated by best technologies available. This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous silica, called frustule. We have studied the optical properties of Arachnoidiscus sp. single valves both in visible and ultraviolet range. We found photonic effects due to diffraction by ordered pattern of pores and slits, accordingly to an elaborated theoretical model. For the first time, we experimentally revealed spatial separation of focused light in different spots, which could be the basis of a micro-bio-spectrometer. Characterization of such intricate structures can be of great inspiration for photonic devices of next generation.

State‐of‐the‐art all‐silicon sub‐bandgap photodetectors at telecom and datacom wavelengths

Abstract: Silicon-based technologies provide an ideal platform for the monolithic integration of photonics and microelectronics In this context, a variety of passive and active silicon photonic devices have been developed to operate at telecom and datacom wavelengths, at which silicon has minimal optical absorption - due to its bandgap of 112 eV Although in principle this transparency window limits the use of silicon for optical detection at wavelengths above 11 μm, in recent years tremendous advances have been made in the field of all-silicon sub-bandgap photodetectors at telecom and datacom wavelengths By taking advantage of emerging materials and novel structures, these devices are becoming competitive with the more well-established technologies, and are opening new and intriguing perspectives In this paper, a review of the state-of-the-art is presented Devices based on defect-mediated absorption, two-photon absorption and the internal photoemission effect are reported, their working principles are elucidated and their performance discussed and compared

Digital self-referencing quantitative phase microscopy by wavefront folding in holographic image reconstruction.

Abstract: A completely numerical method, named digital self-referencing holography, is described to easily accomplish a quantitative phase microscopy for microfluidic devices by a digital holographic microscope. The approach works through an appropriate numerical manipulation of the retrieved complex wavefront. The self-referencing is obtained by folding the retrieved wavefront in the image plane. The folding operation allows us to obtain the correct phase map by subtracting from the complex region of interest a flat area outside the microfluidic channel. To demonstrate the effectiveness of the method, quantitative phase maps of bovine spermatozoa and in vitro cells are retrieved.

PDMS-Based Microfluidic Devices for Cell Culture

Abstract: Microfluidic technology has affirmed itself as a powerful tool in medical and biological research by offering the possibility of managing biological samples in tiny channels and chambers. Among the different applications, the use of microfluidics for cell cultures has attracted much interest from scientists worldwide. Traditional cell culture methods need high quantities of samples and reagents that are strongly reduced in miniaturized systems. In addition, the microenvironment is better controlled by scaling down. In this paper, we provide an overview of the aspects related to the design of a novel microfluidic culture chamber, the fabrication approach based on polydimethylsiloxane (PDMS) soft-lithography, and the most critical issues in shrinking the size of the system.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

Micrometre-scale silicon electro-optic modulator

Abstract: Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.

Silicon optical modulators

Abstract: Optical technology is poised to revolutionize short-reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such an interconnect is the optical modulator. Modulators have been improved dramatically in recent years, with a notable increase in bandwidth from the megahertz to the multigigahertz regime in just over half a decade. However, the demands of optical interconnects are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimizing metrics such as the device footprint and energy requirement per bit, while also maximizing bandwidth and modulation depth, is non-trivial. All of this must be achieved within an acceptable thermal tolerance and optical spectral width using CMOS-compatible fabrication processes. This Review discusses the techniques that have been (and will continue to be) used to implement silicon optical modulators, as well as providing an outlook for these devices and the candidate solutions of the future.

A high-speed silicon optical modulator based on a metal–oxide–semiconductor capacitor

Abstract: Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics1. One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III–V semiconductor compounds2,3,4,5,6 and/or electro-optic materials such as lithium niobate7,8,9. To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only ∼20 MHz (refs 10, 11), although it has been predicted theoretically that a ∼1-GHz modulation frequency might be achievable in some device structures12,13. Here we describe an approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.