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.

3D visualization and biovolume estimation of motile cells by digital holography

Abstract: For the monitoring of biological samples, physical parameters such as size, shape and refractive index are of crucial importance. However, up to now the morphological in-vitro analysis of in-vitro cells has been limited to 2D analysis by classical optical microscopy such as phase-contrast or DIC. Here we show an approach that exploits the capability of optical tweezers to trap and put in self-rotation bovine spermatozoa flowing into a microfluidic channel. At same time, digital holographic microscopy allows to image the cell in phase-contrast modality for each different angular position, during the rotation. From the collected information about the cell’s phase-contrast signature, we demonstrate that it is possible to reconstruct the 3D shape of the cell and estimate its volume. The method can open new pathways for rapid measurement of in-vitro cells volume in microfluidic lab-on-a-chip platform, thus having access to 3D shape of the object avoiding tomography microscopy, that is an overwhelmed and very complex approach for measuring 3D shape and biovolume estimation.

Digital holographic self-referencing quantitative phase microscopy

Abstract: A numerical method to easily obtain a quantitative phase map of objects flowing in micro-fluidic devices using a digital holographic microscope is shown. The presented technique is called digital self-referencing because the retrieved wavefront is folded in order to subtract the area outside the micro-fluidic channel from the area where the sample is.

Fabrication and Characterization of a Back-Illuminated Resonant Cavity Enhanced Silicon Photo-Detector Working at 1.55 μm

Abstract: In this article, the realization and characterization of a new kind of resonant cavity enhanced photo-detector, fully compatible with silicon microelectronic technologies and working at 1.55 μm, are reported. The detector is a resonant cavity enhanced structure incorporating a Schottky diode, and its working principle is based on the internal photo-emission effect. A comparison between a Schottky diode (Al/Si or Cu/Si) and the Schottky diode fed on a high-reflectivity Bragg mirror is carried out. Considering Al as Schottky metal, no difference in responsivity is obtained; considering Cu as Schottky metal, a three-fold responsivity improvement is experimentally demonstrated.

Fiber Bragg Grating sensor monitoring with thermally-tuned Fabry-Perot cavity integrated in an all-silicon rib waveguide

Abstract: Fiber Bragg Gratings (FBG) sensors are a very promising solution for strain and/or temperature monitoring in hostile or hazardous environments. In particular, their typical immunity to EMI and the absence of electrical signals and cables, encourage the use of FBG sensors in aerospace structure. Moreover, FBG sensors can be embedded in composite materials, allowing the fabrication of the so-called smart-materials. In this paper we experimentally demonstrate that a Fabry-Perot cavity, integrated in a low-loss all-silicon rib waveguide, and realized by standard dry etching technique, is suitable for FBG monitoring. The reflected signal for the sensor passes through the cavity which is tuned by means of thermo-optic effect. The optical circuit ends with a photodetector that, for each tuning step, produces a photocurrent proportional to the convolution integral between the FBG and the FP spectral response. Because the finesse of a silicon FP cavity in air is not so high (about 2.5), it is advantageous an extended tuning over a wavelength range longer than the cavity free spectral range, that is convolving the FBG response with more than one FP transmission peak. The photodetector output signal, once acquired, is elaborated using standard FFT algorithm and pass-band filtered, in order to extract the main harmonic. After a final I-FFT step, a fitting procedure returns the FBG reflection peak position. The experimental accuracy, using as reference the peak wavelength measure made with a commercial high-performance Optical Spectrun Analizer, is in the order of few tenths of picometers.

Pyroelectric effect Investigation on LiNbO 3 crystal under humidity conditions using microheater

Abstract: Pyroelectric effect (PE) under humidity conditions from the −Z surface of Lithium Niobate (LiNbO 3 ) crystal was investigated using a Fan shape microheater fabricated on the +Z surface of the crystal. Thermal analyses of the microheater were performed using COMSOL multiphysics and thermal sensor respectively. A resistive Aluminum (Al) sensor was integrated along the microheater in order to control the temperature variation effect from the microheater.

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.