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Showing papers by "Amnon Yariv published in 1990"


Journal ArticleDOI
TL;DR: It is shown that the highest ratio is achieved in the limit of a distributed amplifier, but that, alternatively, periodic amplification at intervals of alpha(-1) entails a penalty of less than 2 dB compared with the (ideal) distributed case.
Abstract: The detected signal-to-noise power ratio is evaluated for fiber links with periodic amplification. It is shown that the highest ratio is achieved in the limit of a distributed amplifier (g = α), but that, alternatively, periodic amplification at intervals of α^-1 entails a penalty of less than 2 dB compared with the (ideal) distributed case.

85 citations


Journal ArticleDOI
TL;DR: In this paper, a two-section multiple quantum well laser is passively mode locked without an external cavity at ∼108 GHz, and the pulse widths average 2.4 ps and have a time-bandwidth product of 1.1.
Abstract: A two‐section multiple quantum well laser is passively mode locked without an external cavity at ∼108 GHz. The pulse widths average 2.4 ps and have a time‐bandwidth product of 1.1. Self‐pulsations at frequencies up to 8 GHz are also observed.

70 citations


Journal ArticleDOI
TL;DR: In this paper, a hybrid beam epitaxy and liquid-phase epitaxy technique was used to construct a constrained-layer InGaAs-GaAs single-quantum-well buried-heterostructure laser with a 3-dB modulation bandwidth of 7.6 GHz at low bias current (14 mA).
Abstract: Strained-layer InGaAs-GaAs single-quantum-well buried-heterostructure lasers were fabricated by a hybrid beam epitaxy and liquid-phase epitaxy technique. Very low threshold currents, 2.4 mA for an uncoated laser (L=425 mu m) and 0.75 mA for a coated laser (R approximately 0.9, L=198 mu m), were obtained. A 3-dB modulation bandwidth of 7.6 GHz was demonstrated at low bias current (14 mA). Procedures for material preparation and device fabrication are introduced. >

50 citations


Proceedings ArticleDOI
17 Jun 1990
TL;DR: A report is presented on the design, fabrication, and testing of a neural network integrated circuit with 65536 analog programmable synapses (256 fully interconnected neurons) based on a generic architecture that the authors proposed (1987).
Abstract: A report is presented on the design, fabrication, and testing of a neural network integrated circuit with 65536 analog programmable synapses (256 fully interconnected neurons). The integrated circuit utilizes charge-coupled devices (CCDs) based on a generic architecture that the authors proposed (1987). Preliminary testing of the CCD neural processor indicates that the operating speed is 0.5t109 analog interconnect updates/s. Loading of the synaptic interaction matrix can be accomplished either electrically or optically within 0.5 ms or 1 ms, respectively

26 citations


Proceedings Article
21 May 1990
TL;DR: In this paper, the Langevin-oscillator equation for the phase statistics of the laser field was solved and applied to a statistical noise analysis of the scattering problem in the fiber.
Abstract: Any conceivable configuration which involves the propagation of a laser beam in a (single-mode) fiber results in a mixing between the main beam and the Rayleigh scattering from the thermodynamically frozen inhomogeneities. This mixing converts phase fluctuations in the output of the laser to intensity fluctuations.1 We have solved the laser Langevin-oscillator equation for the phase statistics of the laser field and then applied the result to a statistical noise analysis of the scattering problem in the fiber. The result is a set of expressions for the total scattered power under a variety of experimental configurations and for the spectrum of the intensity fluctuations.

25 citations


Proceedings Article
21 May 1990
TL;DR: In this article, a monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported.
Abstract: A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two‐state optical memory is demonstrated.

25 citations


Patent
19 Mar 1990
TL;DR: In this paper, a neural processor implemented on a VLSI circuit chip is described, which is capable of entering a matrix T into an array of photosensitive devices which may be charge coupled or charge injection devices (CCD or CID).
Abstract: Several embodiments of neural processors implemented on a VLSI circuit chip are disclosed, all of which are capable of entering a matrix T into an array of photosensitive devices which may be charge coupled or charge injection devices (CCD or CID). Using CCD's to receive and store the synapses of the matrix T from a spatial light modulator, or other optical means of projecting an array of pixels, semiparallel synchronous operation is achieved. Using CID's, full parallel synchronous operation is achieved. And using phototransistors to receive the array of pixels, full parallel and asynchronous operation is achieved. In the latter case, the source of the pixel matrix must provide the memory necessary for the matrix T. In the other cases, the source of the pixel matrix may be turned off after the matrix T has been entered and stored by the CCD's or CID's.

24 citations


Patent
14 May 1990
TL;DR: In this paper, a charge domain bit serial vector matrix multiplier for real-time signal processing of mixed digital/analog signals for implementing opto-electronic neural networks and other signal processing functions is presented.
Abstract: A charge domain bit serial vector matrix multiplier for real time signal processing of mixed digital/analog signals for implementing opto-electronic neural networks and other signal processing functions. A combination of CCD and DCSD arrays permits vector/matrix multiplication with better than 10 11 multiply accumulates per second on a one square centimeter chip. The CCD array portion of the invention is used to load and move charge packets into the DCSD array for processing therein. The CCD array is also used to empty the matrix of unwanted charge. The DCSD array is designed to store a plurality of charge packets representing the respective matrix values such as the synaptic interaction matrix of a neural network. The vector multiplicand may be applied in bit serial format. The row or sensor lines of the DCSD array are used to accumulate the results of the multiply operation. Each such row output line is provided with a divide-by-two/accumulate CCD circuit which automatically compensates for the increasing value of the input vector element's bits from least significant bit to most significant bit. In a similar fashion each row output line can be provided with a multiply-by-two/accumulate CCD circuit which automatically accounts for the decreasing value of the input vector element's bits from most significant bit to least significant bit. The accumulated charge packet output of the array may be preferably converted to a digital signal compatible with the input vector configuration by utilizing a plurality of analog-to-digital converters.

19 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that a proper choice of the longitudinal distribution of the gain as well as that of the magnitude of the grating coupling coefficient will lead to a uniform intensity distribution in distributed feedback lasers.
Abstract: Power‐dependent nonuniform longitudinal intensity distribution leading to spectral and spatial instabilities is a major problem in semiconductor lasers. It is shown theoretically that a proper choice of the longitudinal distribution of the gain as well as that of the magnitude of the grating coupling coefficient will lead to a uniform intensity distribution in distributed feedback lasers. We also show that the widely used phase, rather than magnitude, control of the coupling coefficient cannot lead to a uniform intensity distribution when the facet reflectivities are zero.

18 citations


Patent
15 Oct 1990
TL;DR: In this paper, the authors proposed a two-transistor implementation of a neural network, where one of the transistors at each synapse is composed of a floating gate electrode and a control electrode which permits learning upon application of incident ultraviolet light.
Abstract: A synapse for neural network applications providing four quadrant feed-forward and feed-back modes in addition to an outer-product learning capability allowing learning in-situ. The invention, in its preferred embodiment, utilizes a novel two-transistor implementation which permits each synapse to be built in an integrated circuit chip surface area of only 20 by 20 micrometers. One of the two transistors at each synapse of the present invention comprises a floating gate structure composed of a floating gate electrode and a control electrode which permits learning upon application of incident ultraviolet light. During ultraviolet light application, a floating gate electrode voltage may be altered to modify the weight of each synapse in accordance with preselected criteria, based upon the input and output weight change vector elements corresponding to that particular matrix element. The second transistor corresponding to each synapse of the present invention provides a novel method for applying a voltage to the control electrode of the aforementioned floating gate structure of the first transistor. The voltage applied to the control electrode and thus the proportionate change in the floating gate electrode of the first transistor may be made proportional to the product of the corresponding input weight change vector element and the corresponding output weight change vector element, by using slope controllable ramp generators and phase controllable pulse generators, only one set of which must be provided for the entire matrix of synapses herein disclosed.

16 citations


Journal ArticleDOI
TL;DR: It is shown theoretically that the incorporation of a frequency-dependent loss mechanism in a semiconductor laser can lead, in concert with the amplitude-to-phase coupling, to major reductions of the fundamental intensity and phase noise.
Abstract: We show theoretically that the incorporation of a frequency-dependent loss mechanism in a semiconductor laser can lead, in concert with the amplitude-to-phase coupling, to major reductions of the fundamental intensity and phase noise. A loss dispersion of the wrong sign, on the other hand, leads to an increase of the noise and, at a certain strength, to instability.

Journal ArticleDOI
TL;DR: In this article, electron microprobe analysis is used to determine the density of Cu1+ and Cu2+ ions in a photorefractive KTa1−x Nbx O3 :Cu,V sample.
Abstract: Absorption measurements and electron microprobe analysis are used to determine the density of Cu1+ and Cu2+ ions in a photorefractive KTa1−x Nbx O3 :Cu,V sample. Photorefractive measurements are made over a wide range of Cu1+ and Cu2+ concentrations, altered by a series of oxidation and reduction treatments. Diffraction efficiencies were varied by over an order of magnitude while erasure rates were varied by over two orders of magnitude.

Journal ArticleDOI
TL;DR: This first report on the photorefractive properties of Rh-doped Sr(0.6)Ba( 0.4)Nb(2)O(6) and experimental results showing a reduction of the photOREfractive two-beam coupling response time by more than an order of magnitude with an external dc field of 10 kV/cm are presented.
Abstract: We present what is to our knowledge the first report on the photorefractive properties of Rh-doped Sr0.6Ba0.4Nb2O6 and experimental results showing a reduction of the photorefractive two-beam coupling response time by more than an order of magnitude with an external dc field of 10 kV/cm.

Journal ArticleDOI
TL;DR: In this paper, a monolithic InGaAs/AlGaAs double quantum well laser at a wavelength of 985 [angstroms] was generated with a 42GHz repetition rate.
Abstract: Pulse trains with a 42GHz repetition rate were generated by monolithic InGaAs/AlGaAs double quantum well lasers at a wavelength of 985 [angstroms]. The cavity was electrically divided into three regions, one providing gain and the other two providing saturable absorption. The optical modulation has a depth greater than 98% and full-width at half-maximum under 6ps, and bias conditions for sustained mode-locking are determined.

Journal ArticleDOI
TL;DR: In this article, a buried crescent laser on a P-InP substrate was demonstrated with a cavity length of 300μm, a maximum CW power of 130mW at room temperature, and 3dB bandwidth in excess of 12GHz at an output power of 52mW.
Abstract: A simultaneous operation of a semiconductor laser at high power and high speed was demonstrated in a buried crescent laser on a P-InP substrate. In a cavity length of 300μm, a maximum CW power of 130mW at room temperature was obtained in a junction-up mounting configuration. A 3dB bandwidth in excess of 12GHz at an output power of 52mW was observed.

Journal ArticleDOI
TL;DR: In this paper, the effect of dielectric coatings on semiconductor laser performance is investigated and it is demonstrated that the dielectrics are a powerful means of controlling the laser threshold current, external quantum efficiency, maximum output power, longitudinal mode behaviour, lasing wavelength and spectral linewidth.
Abstract: Experimental studies and theoretical analyses on the effect of dielectric coatings on semiconductor laser performance are presented. It is demonstrated that the dielectric coating technique is a powerful means of controlling the laser threshold current, external quantum efficiency, maximum output power, longitudinal mode behaviour, lasing wavelength and spectral linewidth.

Journal ArticleDOI
TL;DR: In this paper, the authors present experimental results of fieldenhanced photorefractive two-beam coupling and gain in Cr•doped strontium barium niobate crystals and its dependence on dopant concentrations.
Abstract: We present experimental results of field‐enhanced photorefractive two‐beam coupling and gain in Cr‐doped strontium barium niobate crystals and its dependence on dopant concentrations. Increases in the exponential gain factor by more than a factor of 2 were observed by applying a field of up to 10 kV/cm. This property has potential applications such as switchable optical phase conjugators, limiters, and thresholding devices.

Patent
07 Jun 1990
TL;DR: In this article, the authors proposed a non-destructive charge domain multiplier and process thereof wherein the unique characteristics of the charge coupled device permits sensing the size of a charge packet as it moves past an electrode and creating a new charge packet proportional to the product of the original packet and an externally applied value.
Abstract: A non-destructive charge domain multiplier and process thereof wherein the unique characteristics of the charge coupled device permits sensing the size of the charge packet as it moves past an electrode and creating a new charge packet proportional to the product of the original packet and an externally applied value. The device non-destructively senses the size of the charge packet and multiplies it with another value using a multiple metering gate variation of the "Fill and Spill" technique. The present invention therefore constitutes a unique CCD configuration which creates as an output, a charge packet proportional to the product of the charge in an input packet and an externally applied value. Thus, the present invention enables the performance of non-linear operations by CCD integrated circuits.

Proceedings ArticleDOI
04 Jan 1990
TL;DR: In this article, the growth of doped Potassium Tantalate Niobate (KTN) crystals and the characterization of their photorefractive properties L. the paraelectric region were reported.
Abstract: We report the growth of doped Potassium Tantalate Niobate (KTN) crystals, and the characterization of their photorefractive properties L. the paraelectric region. First the Top Seeded Solution Growth Method is reviewed and the growth process of a KTN:Cu,V crystal is described. Results of diffraction efficiency measurements of photorefractive gratings in these crystals at the paraelectric phase, are then presented. These experiments show high diffractio- efficiencies, and indicate the possibility of amplitude modulation of the gratings by an external field. Results showing fixation of the gratings when the sample is close to the phase transition temperature are also described.

Book ChapterDOI
01 Jan 1990
TL;DR: Asimple circuit architecture in standard CMOS technology for the optoelectronic implementation of analog continuous-time neural networks (NN) is presented, which enables the implementation of recurrent NN models with analog synapses and neurons, with continuous dynamics.
Abstract: Asimple circuit architecture in standard CMOS technology for the optoelectronic implementation of analog continuous-time neural networks (NN) is presented. The circuit enables the implementation of recurrent NN models with analog synapses and neurons, with continuous dynamics. The basic cell consists of a synapse coupled with a distributed neuron, where synaptic linear superposition and neuron nonlinear thresholding are combined together, using only five MOS transistors and one phototransistor per synapse. The synaptic interaction matrix is imaged continuously on the chip from a spatial light modulator, thus allowing fast reprogramming of the connections. The performance of the proposed system is illustrated by some measurements of synapse and neuron characteristics on a 16 neuron (256 synapse) prototype fabricated in MOSIS CMOS technology. The expected performance and limitations of a scaled up system are discussed.

Proceedings ArticleDOI
22 May 1990
TL;DR: A generic architecture for realizing neural networks is presented in which the synaptic interaction matrix is loaded in parallel into an electronic integrated circuit from a SLM.
Abstract: A generic architecture for realizing neural networks is presented in which the synaptic interaction matrix is loaded in parallel into an electronic integrated circuit from a SLM. Three types of the electronic processors are described using CCD, CID and CMOS technologies respectively. The pros and cons of currently existing SLMs for this architecture are pointed out.

Journal ArticleDOI
TL;DR: In this article, a double-carrier InGaAsP-InP laser with two active layers was fabricated to study the temperature behavior of the doublecarrier-confinement structure and an anomalously high characteristic temperature T/sub 0/ was measured, and optical switching behavior was observed.
Abstract: A buried crescent InGaAsP-InP laser with two active layers was fabricated to study the temperature behavior of the double-carrier-confinement structure An anomalously high characteristic temperature T/sub 0/ was measured, and optical switching behavior was observed A mode analysis and numerical calculation using a rate equation approach explained qualitatively very well the experimental results It was revealed that both the Auger recombination in this special double-active-layer configuration and the temperature-dependent leakage current, which leads to uniform carrier distribution in both active regions, are essential to increase T/sub 0/ >

Proceedings ArticleDOI
04 Jan 1990
TL;DR: The photorefractive effect in Cr-doped strontium barium niobate (SBN:60) and SBN:75 was investigated in this article.
Abstract: Cr-doped strontium barium niobate has shown significant reduction in the time of response compared to previously grown Ce-doped crystals, with room temperature response times as short as 0.2 sec. The experimental photorefractive two-beam coupling gain and response time of 1% and 1.6% Cr-doped SBN:60 and 1% Cr-doped SBN:75 will be presented and compared to results in Ce-doped SBN:60. The photorefractive effect in Cr-doped SBN:60 has also shown a strong temperature dependence, with gain increasing by a factor of two when the crystal was cooled from 40 to -20° C. Significant gain enhancement was also predicted and obtained by applying a DC electric field of up to 10 kV/cm.

01 Jul 1990
TL;DR: In this paper, the authors used radiometric, density of states (material), and thermal considerations to obtain the figure of merit of the quantum-well GaAs/GaAlAs infrared detectors described by Smith et al.
Abstract: Radiometric, density of states (material), and thermal considerations are used to obtain the figure of merit of the quantum-well GaAs/GaAlAs infrared detectors described by Smith et al The results are compared with HgCdTe, the present industry standard, as well as with recent experiments at other laboratories

Proceedings ArticleDOI
01 May 1990
TL;DR: In this paper, the spectral tunability of properly designed quantum well lasers is demonstrated to equal the range of dye lasers, and theoretical and measured gain spectra are presented to support this statement.
Abstract: The spectral tunability of properly designed quantum well lasers is demonstrated to equal the range of dye lasers. Theoretical and measured gain spectra are presented to support this statement, and stepwise wavelength tuning over a 125 nm span in GaAs/AlGaAs lasers and 175 nm in InGaAs/AlGaAs lasers are shown.

Proceedings ArticleDOI
23 Jan 1990
TL;DR: In this article, a detailed design for a 5 Gbit s-1 transmission rate, suppression of pattern effects, and a system power supply of approximately 25 mW per laser is presented.
Abstract: Optical computer interconnects appear very attractive when integration of state of the art technology of quantum well GaAs/GaA1As lasers is considered These ultralow threshold lasers provide the very high transmission rates and the inherent simplicity required for such systems A detailed design is presented for a 5 Gbit s-1 transmission rate, suppression of pattern effects, and a system power supply of approximately 25 mW per laser Existing experimental data show that little extrapolation is required to reach that kind of performance from state of the art technology