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.

Characterization of an electrically induced refractive index change in a hydrogenated amorphous silicon multistack waveguide

Abstract: Electrically induced phase modulation is characterized for the first time in a waveguide-integrated Fabry-Perot (FP) resonating cavity based both on an index- and conductivity high-contrast amorphous silicon/amorphous silicon carbide (a-Si:H/a-SiC:H) multistack.

Lateral shearing interferometer for measuring refractive index of silicon

Abstract: A simple lateral shearing interferometer is proposed for measuring refractive index of thin parallel plate silicon sample. The rotating sample works as lateral shearing element. As the sample rotates a continuous lateral shearing is obtained owing to the change of the optical path difference (OPD) between the transmitted beam and that first reflected by the surface sample. The recorded interferometric signal is Fourier-transform analyzed and the phase change is determined as a function of the rotating angle. If the thickness of the silicon sample is known the method provides accurate measurement of the refractive index. ( Summary only available )

A novel interferometric spectrometer obtained by imaging Talbot effect in digital holography

Abstract: We present here the observation of the Talbot effect in digital holography (DH). A self-imaging phenomena is observed by reconstructing the amplitude of the object wavefield by using different distances and different illumination wavelengths. The numerical reconstruction allows to determine the complex field amplitude at different wavelengths while maintaining constant the reconstruction distance. We investigate on the possibility to build a spectrometer based on the Talbot effect. In particular, the spectrometer proposed in this work can cover the whole visible spectrum ranging from 350 nm to 750 nm and, from the FWHM of the spectrograms with a resolution of about 20 nm

Detecting vibrations by fiber Bragg sensor interrogated with a bipolished silicon sample

Abstract: In this paper a new method for reading out Bragg wavelength shifts experienced by fiber Bragg gratings is described. The system is based on a bi-polished silicon sample acting like a Fabry-Perot filter. The spectral response of the Silicon Fabry-Perot filter allows to convert the Bragg wavelength shift into a variation of the light intensity, which can be read by a photodiode. The method efficacy is proved monitoring dynamic strain characteristics of a simple structure. So, the vibration mode of an aluminium cantilever has been sensed by means a FBG sensor attached on the surface of the cantilever itself. In proposed demodulation method the sensitivity and accuracy depend on the spectral band width of the filter. The filter can be designed according to the range of the amplitude vibrations, assuring linear response of system, as function of the thickness of the silicon sample. Moreover, thank to great tuning capability of the Silicon Fabry-Perot filter, it is possible to place Bragg grating spectral response on the central portion of the linear region of the FP response.

Thermo-opto-electrical analysis of an optical modulator integrated in a silicon planar structure

Abstract: Interest in silicon as a material for optoelectronics has increased year after year. We propose numerical analysis of an integrated waveguide-vanishing-based modulator realized by ion implantation in SOI wafer. The active region is 3u 3 µm 2 and the lateral confinement is guaranteed by two highly-doped As (8×10 19 cm -3 ) and B (2×10 19 cm -3 ) implanted regions 1-µm -deep. This type of structure allows to obtain a planar device, avoiding structural steps which are harmful for photolithography processes. The resulting channel waveguide shows single mode operation and propagation losses of about 1.8 dB/mm , which are acceptable for short structures. The modulation is based on a lateral p-i-n diode, which injects free carriers into the rib volume between the doped regions. We have optimized the device for maximum injection efficiency for a given applied voltage. The resulting optical behavior can be explained by the lateral confinement vanishing that transforms the rib waveguide in a slab waveguide, once the rib is full of free carriers. This phenomenon occurs at driving voltage of about 1.0 V , with electrical power consumption below 1 mW , and implies a rapid variation of the propagating characteristics, and as consequence an optical beam lateral redistribution into the structure. Results show that an optical modulation depth close to 100 % can be reached with a switching time of about 30 ns . A set of numerical simulations has been performed in order to evaluate the thermal response of the device and thus to estimate the ther mo-optic effect related to the biasing of the device itself. The main advantages of this device are the low cost and fu ll integrability with electronic devices; thus the device can be suitable in many application fields. Keywords: Optoelectronic devices, integrated optics, optical modulators.

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.