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.

Interferometric measurement of thickness of silicon nitride layer in bi-morph silicon MEMS

Abstract: In this paper is reported a method for measuring the thickness of a silicone nitride layers employed for fabricating silicon MEMS bi-morph structures. The method allows the precise evaluation of layer thickness by adopting Digital Holographic Microscope. The measurement is based on the fact that the silicon nitride layer is transparent to the visible light. The optical phase difference (OPD) between the light beam traveling through the layer and portion of the beam in air is measured exploiting an interferometric technique. The approach is very simple and can be utilized even for inspection of non-planar or stressed structures. Experimental values have been compared with ellipsometric measurements.

How to extend depth of focus in 3D digital holography

Abstract: In microscopy, high magnifications are achievable for investigating micro-objects but the paradigm is that higher the required magnification, the lower the depth of focus. In this paper we show that it is possible to construct an extended focused image (EFI) image by a coherent optical microscope without any mechanical movement but by using the 3D imaging capability of digital holography (DH). In fact, DH has the unique property of allowing direct calculation and management of an amplitude and phase map along the longitudinal direction in front of the digital camera. That constitutes a fundamental feature of DH to construct an EFI image of an object or systems experiencing dynamic evolution since the recording of only one image is needed instead of performing a mechanical scanning and to record several images at different focus planes. In other words, by means of this approach it is possible to obtain an EFI image for studying dynamic objects, such as biological objects, dynamic MEMS.

Method and apparatus for discriminating x and y sperms based upon raman spectroscopy

Abstract: The invention relates to a method based upon the use of Raman spectroscopy to face the problem of the biochemical analysis and of the differentiation of the X sperm and Y sperm in the animal species, in particular bovine species, with approaches which make possible the subsequent use in fecundation techniques. A method addressed to the resolution of this problem is based upon the separation between X sperm and Y sperm before insemination. An apparatus is also described implementing such method which allows to distinguish and characterize the difference between X sperm and Y sperm by acquiring and analyzing Raman spectra noninvasively and in a not destructive way. By means of a statistical approach, such as for example the analysis of the main components and the linear discriminating analysis, the spectroscopic difference between X sperm and Y sperm is evaluated, processed and used to separate the two types of cells. The invention also relates to the development of a cytofluorimeter combining the Raman microscope with a system for trapping optically the sperms and a microfluidic chamber. More precisely, the optical trapping system, equipped with an objective with high numerical aperture, is used to immobilize the cells and, the same objective is used to excite and gather Raman spectra. At last, the microfluidic chamber is used to make the sample to flow, with the final purpose of providing a quick, precise and not invasive separation of X sperm and Y sperm, (figure 5A).

Analysis of bovine sperm cells by a combined holographic and Raman microscopy approach

Abstract: In this work, an approach based on digital holography (DH) combined with Raman spectroscopy (RS) is used for a complete label-free analysis of single bovine spermatozoa. DH allows to obtain high-resolution images of bovine sperm from the reconstruction of a single acquired hologram, highlighting in some cases morphological alterations. Quantitative 3D reconstructions of sperm head, both normal and anomalous, have been studied and an unexpected structure of the post-acrosomal region of the head has been detected. Raman imaging analysis have also confirmed such anomalies, suggesting the protein vibrations as associated Raman marker of the defect.

Design, fabrication and testing of an integrated Si-based light modulator: experimental evidence of plasma redistribution

Abstract: The implementation of efficient Si-based optical functions has attracted a considerable interest in the last years since it would allow the use of the Si technology for the realization of integrated optoelectronic devices. We have fabricated and characterized a novel Si-based light modulator working at the standard communication wavelength of 1.54 micrometers . It consists of a three terminal Bipolar Mode Field Effect Transistor integrated with a silicon RIB waveguide on epitaxial Si wafers. The optical channel of the modulator is embodied within its vertical electrical channel. Light modulation is obtained through the formation of a plasma of carriers, inside the optical channel, that produces an increase of the absorption coefficient. Fast modulation is achieved by moving the plasma inside and outside the optical channel by properly biasing the control electrode. The devices have been fabricated using clean room processing. Detailed electrical characterization and device simulation confirm that strong conductivity modulation and plasma formations in the channel are achieved. The plasma distribution in the device under different bias conditions has been directly derived from Emission Microscopy analysis. The expected device performances in terms of modulation depth and speed will be presented and discussed.

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.