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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, a porous silicon-based Bragg grating integrated in an optical waveguide, by using a low-cost and fast technique, direct laser writing, has been obtained.
Abstract: We have designed, fabricated and characterized a porous silicon-based Bragg grating integrated in an optical waveguide, by using a low cost and fast technique, direct laser writing. A periodic optical structure with a pitch of 10 µm, resonant in the near-infrared wavelength region, has been obtained. The simulated transmission spectra, calculated by the transfer matrix method and waveguide modal computation, are in good qualitative agreement with the experimental ones. The waveguide transmission losses have been quantified as 22 dB cm−1.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated a photodetector operating at 1550 nm whose detection mechanism is based on the internal photoemission effect through an Er/Si Schottky junction.
Abstract: In the last two decades there has been growing interest in silicon photonics and in the possibility to integrate new materials to overcome the silicon intrinsic limitations. Erbium has represented a viable solution for the realization of light sources at telecommunications wavelengths opening the path to the investigation of various photonic devices based on rare earth. In this work we investigate a photodetector operating at 1550 nm whose detection mechanism is based on the internal photoemission effect through an Er/Si Schottky junction. The Er/Si junction has been carefully electrically characterized showing a potential barrier and cut-off wavelength of 0.59 eV and 2105 nm, respectively. Moreover, a responsivity of 0.62 mA/W has been measured for a 3 μm-width waveguide at 1550 nm and at reverse voltage of -8 V. Finally, the noise equivalent power of the device has been evaluated as high as 0.53 nW/(Hz)1/2 at -8 V. Even if device responsivity is still low, we believe that our insights may suggest Er/Si as a new platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.

6 citations

Journal ArticleDOI
TL;DR: In this article, the performance of different configurations of a-Si:H-based electro-optical amplitude modulators integrated into passive waveguides is discussed, based on the plasma dispersion effect, a phenomenon that allows them to reach useful performance at the communication wavelength of 1.55m.
Abstract: Hydrogenated amorphous silicon (a-Si:H) has recently emerged as a promising material to provide microchips with passive and active photonic functions through a back-end and CMOS-compatible technological process. In this paper, we discuss the performance achieved with different configurations of a-Si:H-based electro-optical amplitude modulators integrated into passive waveguides. All of the analysed devices are based on the plasma dispersion effect, a phenomenon that allows us to reach useful performance at the communication wavelength of ? ? 1.55??m. The behaviour of the various proposed modulation approaches has been tested by ad hoc interferometric structures, such as Fabry?Perot integrated resonators or integrated Mach?Zehnder interferometer, as well as by multistack devices to enhance the static modulation efficiency. The performance of each modulator has been analysed through several figures of merit.

6 citations

Journal ArticleDOI
TL;DR: It is made the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome.
Abstract: Morphological selection techniques of gametes and embryos are of current interest to clinical practice in ART. Although intracytoplasmic morphologically selected sperm injection (IMSI), time lapse imaging morphometry (TLIM) or quantification of chromosome numbers (PGS) are potentially useful in research, they have not been shown to be of statistically predictive value and, thus, have only limited clinical usefulness. We make the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome. Since previous attempts to identify metabolic markers for embryo quality have failed and there is no evidence that the intrinsic nature of gametes and embryos can be improved in the laboratory, embryologists can only minimize environmental or operator induced damage while these cells are manipulated ex vivo.

6 citations

Journal ArticleDOI
TL;DR: Preliminary gene mapping analysis revealed that the closest loci to these fragile sites contain genes such as RASA1 and CAST, NPR3 and C9, whose mutations are responsible for severe phenotypic malformations and immunodeficiency in humans and mice, and meat quality in pigs.
Abstract: A fragile-site map has been preliminarily established in the standard karyotype of river buffalo (Bubalus bubalis, 2n=50) with the aim of unmasking ‘weak’ chromosomal regions in the karyotype of the species. The majority of the breakages took place in the RBA/RBG-negative bands or at the band-interband regions. The most fragile chromosomes were identified as the inactive X, chromosomes 9 and 8, and the active X, with 42, 32, 31 and 30 breakages, respectively. The 400 breakages were distributed in 106 breaksites (BS), with an average intensity of 4 breaks per chromosomal site; (b) the most fragile bands of the river buffalo karyotype were identified as 9q213 with 24 breaks, band 19q21 with 16; inacXq24 with 15; bands 15q23 and 17q21 with 13; band 13q23 with 12, and so on. Preliminary gene mapping analysis revealed that the closest loci to these fragile sites contain genes such as RASA1 and CAST (9q214), NPR3 and C9 (19q19), OarCP09 (15q24), PLP and BTK (Xq24-q25) and EDNRB (13q22), whose mutations are responsible for severe phenotypic malformations and immunodeficiency in humans and mice, and meat quality in pigs. Further cytogenetic and molecular studies are needed to fully exploit the biological significance of the fragile sites in the karyotypes of domestic animals and their relationships with productive and reproductive efficiency.

5 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
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 …

33,785 citations

Proceedings Article
01 Jan 1999
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and 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.
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.

2,722 citations

Journal ArticleDOI
19 May 2005-Nature
TL;DR: Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures, and here a high-speed electro-optical modulator in compact silicon structures is experimentally demonstrated.
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.

2,336 citations

Journal ArticleDOI
TL;DR: The techniques that have, and will, be used to implement silicon optical modulators, as well as the outlook for these devices, and the candidate solutions of the future are discussed.
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.

2,110 citations

Journal ArticleDOI
12 Feb 2004-Nature
TL;DR: An approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation is described and an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz is demonstrated.
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.

1,612 citations