bluuebunny/crossref_metadata_2025 huggingface dataset:
Limitations of the Impulse Response of GaAs MSM-Photodetectors
Authors: Kuhl J. , Klingenstein M. , Lambsdorff M. , Moglestue C. , Rosenzweig J. , Axmann A. , Schneider Jo. , Hülsmann A.
Published: February 2023

Interdigitated Metal-Semiconductor-Metal (MSM) Schottky diodes fabricated on GaAs and other III-V compounds are sensitive high speed photodetectors for multigigabit optical data processing systems. The compatibility of the fabrication process with the process technology of planar high speed electronic devices like FET's makes them extremely attractive for ultrafast integrated optoelectronic circuits. Narrow Schottky contact spacing permitting rapid carrier extraction after photoexcitation and a small active area in order to minimize the parasistic capacitance are the key design features of these diodes. First attempts to model the intrinsic transport of photoexcited carriers in MSM-diodes by a one-dimensional Monte Carlo simulation predict temporal separation of the electron and hole current /1,2/ and durations of electron and hole pulse of a few picoseconds and several ten picoseconds, respectively. Although frequency bandwidths in excess of several ten GHz for such detectors have been reported by several groups /3,4/ a direct comparison of theoretical and experimental results and a definite identification of the performance-limiting factors is still missing, so far.
Tunnelling and Relaxation in Coupled Quantum Wells
Authors: Deveaud B. , Chomette A. , Clérot F. , Regreny A. , Gurvitz S. , Joseph I. Bar
Published: February 2023

In a double barrier resonant tunnelling diode, the lifetime of the electrons in the well is governed by the coupling of the confined states to the continuum of states outside the barriers. The well states are broadened by the interaction with the continuum on each side of the structure and are thus metastable, even without any relaxation mechanism such as phonon emission. If an electron is injected into the structure as in the experiment of Tsuchyia et al [1], it will leak out with a time constant given only by the barrier thickness.
Transient Simulation of Ultra-Small GaAs MESFET Using Quantum Moment Equations
Authors: Zhou J. , Kriman A. M. , Ferry D. K.
Published: February 2023

Since the advent of the integrated circuits in the late 1950’s, the number of devices contained on a single chip has approximately doubled every three years and this process has caused semiconductor devices to be made smaller and smaller. However, little is understood about the physical limitations that will determine whether or not these devices are practical. These questions have opened a new field for semiconductor research and technology in which a great opportunity is provided to study many new physical phenomena, some of which have been described in [1-4], and exploring a new generation of device structures and system architectures for the potential application of Ultra Large Scale Integrated (ULSI) system in the near future.
Comparison of Oxygen Ion and Proton Implanted GaAs Photoconductive Switches
Authors: Huang Sheng-lung L. , Chauchard Eve A. , Lee Chi H. , Smith Thane , Lee Timothy T. , Joseph Thomas R.
Published: February 2023

On-wafer characterization of MMIC’s performed by optoelectronic techniques such as photoconductive sampling or electro-optic sampling is currently investigated by several groups1. For photoconductive sampling, pulse generation and/or waveform sampling are done by illuminating a photoconductive gap with short laser pulses. In order to integrate monolithically the photoconductive gaps and the device under test, the gaps have to be fabricated with a technology compatible with GaAs MMIC’s fabrication technology. In this work, we characterized and compared two such MMIC-compatible photoconductive gaps. For the photoconductive sampling technique, ultrafast carrier lifetime in the gap is required. A number of approaches2,3 have been tried to reduce carrier lifetime and achieve a higher bandwidth - sensitivity product. Radiation damaged material is commonly used but a major drawback for this approach is the poor sensitivity due to fewer carriers reach the contact and reduced mobility. An O+ implanted switch4,5, which is annealed at 410°C for 10 minutes after implantation to reduce defects has been developed to improve carrier mobility. The implantation was performed at two energies, 140 keV with a dose of 5 × 1011cm−2 and 360 keV with a dose of 1.3 × 1012cm−2. This process is compatible with TRW’s MMIC fabrication process. We characterized the O+ implanted GaAs switch and make a comparison with H
+
implanted GaAs switch.
Electro-Optic Sampling for the Measurement of the Response of Fast Oscillosopes
Authors: Henderson D , Roddie A G , Smith A J A
Published: February 2023

Several new sampling oscilloscopes (CRO) have been introduced in recent years, the fastest claiming step rise times of about 5 ps. Development of these CROs has been driven by rapid developments in areas such as optical fibre communications where they are often the limiting instrument in a measurement. Since these instruments are able to output waveforms to computers, knowledge of the impulse response can be used to increase the speed and accuracy of the CRO measurement (1). The purpose of this paper is to describe the techniques that we have applied to derive the temporal responses of fast sampling CROs.
Photonic Switching Devices Based on Multiple Quantum Well Structures
Authors: Miller D. A. B.
Published: February 2023

Quantum well (QW) structures consist of alternate thin (e.g. 100 Å) layers of two different semiconductors such as GaAs and AlGaAs. Electrons and holes tend to be confined in the semiconductor with the narrower band gap (e.g. GaAs). New physical properties result from this confinement, and these properties can be engineered through choice of layer thicknesses and compositions. One specific consequence of confinement is that the optical absorption spectrum is changed significantly compared to conventional semiconductors, acquiring a steplike structure and also relatively sharp and strong absorption peaks at the edges of the steps even at room temperature. These peaks are called exciton absorption resonances, and they are normally only seen at low temperatures in conventional semiconductors.[1]
Picosecond optical beam coupling in photorefractive GaAs
Authors: Valley George C. , Smirl Arthur L. , Bohnert Klaus , Boggess Thomas F.
Published: February 2023

We recently reported observations of the photorefractive effect in GaAs using beam coupling with 40-picosecond pulses.1 In these observations, several effects interact to modify the transmission of a weak probe pulse in the presence of a strong pump pulse from that experienced by the weak probe pulse alone. The photorefractive effect transfers energy from one beam to the other in a direction controlled by the crystallographic axes.2 Transient energy transfer due to the free-carrier grating transfers energy from the strong pump to the weak probe.3 Two-photon absorption due to the presence of the strong pump causes enhanced probe loss. In addition, effects of lesser importance such as saturation of the donor and acceptor absorption at the EL2 and EL2+ levels, absorption gratings, and free-carrier absorption modify the probe transmission in the presence of the pump.
Wave-Mixing in Non Linear Photorefractive Materials Applications to Dynamic Beam Switching and Deflection
Authors: Huignard Jean-Pierre
Published: February 2023

The exchange of informations at high data rates between optoelectronic transducers is an important task encountered in all advanced architectures of high capacity parallel optical processors and optical transmission links. For these purposes, the use of all-optical techniques for large scale and very broad-band switching is currently the object of active researchs. For a limited number of input-ouput signals, integrated optical technologies using ligth propagation in electro-optic waveguides offer attractive performances. However, for the much larger switching capacities which will be required in the future, for example 1024 x 1024, the most attractive switch architecture should exploit the 2-D parallel space transmission of the optical beams (1-3). Because of the high degree of parallelism of this approach a switching time constant of few milliseconds would be convenient. The potentiel capabilities of such a switching technique are therefore very large, in particular if the connection between any light emitter and receiver can be reconfigured in real-time. The aim of the lecture is to show that the principle of reconfigurable interconnections can be demonstrated on the basis of wave mixing experiments with photorefractive crystals. The operating mode, of a 2-D optical switch is schematically shown in Figure 1. The point to point connection is established through the angular deflection of the beams emerging from the 2-D input light emitter array (semiconductor lasers, single mode fibers...).
The Dynamics of Photonic Switching in Indium Antimonide
Authors: MacKenzie H.A. , Young J. , Al-Attar H.A.
Published: February 2023

To obtain the full data processing potential of optical computing, the practical system may well evolve in the form of fast switching arrays of bistable elements which exploit the innate parallelism of optics. Such arrays will be required to operate efficiently with low incident powers, high switching speed, gain, good tolerance to noise and minimal cross talk between channels. An investigation of these competing criteria has been undertaken with an Indium Antimonide etalon using low power c.w. CO lasers, lead-salt diode lasers and other sources of switching signal.
4 Gb/s Optical Time-Division Multiplexed System Experiments using Ti:LiNbO3 Switch/Modulators
Authors: Tucker R. S. , Korotky S. K. , Eisenstein G. , Koren U. , Raybon G. , Veselka J. J. , Buhl L. L. , Kasper B. L. , Alferness R. C.
Published: February 2023

Optical time-division multiplexing (OTDM) is potentially a useful technique for increasing the bit rate of lightwave systems beyond the bandwidth capabilities of drive electronics. We report here a novel optical multiplexing and demultiplexing scheme using mode-locked extended cavity injection lasers and Ti:LiNbO3 waveguide switch/modulators. An OTDM experiment is described in which two separate lasers are mode-locked and externally modulated at 2 GHz, and then optically multiplexed to a bit rate of 4 Gb/s. The 4Gb/s multiplexed signal is transmitted over 8 km of fiber, demultiplexed with a Ti:LiNbO3 optical directional coupler switch, and received at low error rate. The experiments reported here extend our previous work on external modulation [1], OTDM using gain-switched lasers [2], and our work on mode-locking of extended-cavity injection lasers [3]. The mode-locked lasers provide an excellent means of generating short pulses at high repetition rates, using only narrow-band electronics. In addition, they offer the potential of good spectral purity - a key requirement for low distortion, high bit-rate transmission over long fiber lengths.
Ultrafast All-Optical Switch
Authors: Friberg S. R. , Silberberg Y. , Oliver M. K. , Andrejco M. J. , Saifi M. A. , Smith P. W.
Published: February 2023

The importance of ultrafast all-optical switching devices stems both from their sub-picosecond switching time, which is faster than that feasible with electronic devices, and their compatibility with all-optical fiber data-transmission systems. Much of the work on such devices has been concentrated on optical bistable switches, which require optical materials with large nonlinearities if devices are to be small enough to respond at sub-picosecond speeds. However, waveguide devices such as the nonlinear optical coupler1 or the birefringent fiber polarization switch2 can operate at ultrafast switching rates even when fabricated from glass, a material with a small, fast electronic nonlinearity and a very low absorption.3,4
A Digital Electrooptic Switch
Authors: Silberberg Y. , Perlmutter P.
Published: February 2023

We propose and analyze a new 2X2 electrooptic switch structure that exhibits a step-like response to the switching voltage. This response eliminates the need for precise voltage control for switching, and it therefore enables the operation of many such elements by a single voltage source, as required for switching arrays. Moreover, because this characteristic applies to both polarizations in a lithium niobate device, it can be made polarization independent, and it should be insensitive to the wavelength of light.
Low drive voltage 4X4 Ti:LiNbO3 switch
Authors: Sawaki I. , Yamane T. , Nakajima H.
Published: February 2023

An optical matrix switch is one of the most important components in constructing photonic switching systems. Previously, several strictly non-blocking matrix switches fabricated on Ti:LiNbO3 have been reported[1]-[3]. However, drive voltages of less than 10 V have not been obtained in a matrix larger than 4X4 for 1.3 um wavelength. In this paper, we overcame this problem by a new configuration for the waveguide network.
Optical Broadband Communications Network Architecture Utilizing Wavelength-Division Switching Technologies
Authors: Suzuki Syuji , Nagashima Kunio
Published: February 2023

Substantial needs for broadband communications networks have been increasing with the advent of new technology and growing interest in visual information services. Optical switching systems and optica1-fiber transmission systems will be indispensable to realize future broadband communications networks. In particular, wavelength-division (WD) switching system and wavelength-division multiplexed (WDM) transmission systems, making full use of extremely high optical carrier frequencies and enjoying widely ranging bit-rate independency for individual channels, have potential capability for extension to wide-area broadband networks. This paper proposes optical broadband network architecture using WD switching systems and WDM transmission systems.
Dilated Networks for Photonic Switching
Authors: Padmanabhan Krishnan , Netravali Arun
Published: February 2023

Wideband optical signals can be switched under electical control using directional couplers between Ti:LiNbO3 waveguides on a planar LiNbO3 crystal [1]. The basic switching element is a directional coupler with two active inputs and two active cutouts. Depending on the control voltage at the junction of the two waveguides, either of the two inputs can be coupled to either of the two outputs. Several architectures have been proposed to construct an NxN (N > 2) switch with the 2 x 2 directional coupler as the basic element [2-4]. These architectures are analogs of similar architectures known in electronic switching [5]. However, due to the difference in characteristics of the electronic and optical switching elements, performance and optimization of the optical architectures is significantly different.
Self-Routing Optical Switch with Optical Processing
Authors: Prucnal P. R. , Blumenthal D. J. , Perrier P. A.
Published: February 2023

Self-routing switching architectures can reduce the propagation delay of data through a switching network. In the self-routing process, the data is encoded with a destination address which accompanies it through the switching network. This destination address may be contained in each bit, or in the packet header. Each switching node processes this destination information to route the data through the switch. Propagation delay is reduced by processing the destination address in real time, rather than prior to transmission.
An All-Fibre Routeing Switch
Authors: Mallinson S R , Wright J V , Millar C A
Published: February 2023

A key functional element for advanced single-mode optical fibre networks is a 2x2 crosspoint switch for routeing optical signals (1). Such a switch would be used to configure an optical system and would not necessarily need to have a fast switching characteristic. An all-fibre device would be attractive because of the low transmission loss and ease of coupling to system fibre, and a basic building block for many fibre-based devices is the polished fibre coupler (2).
4×4 Ti:LiNbO3 Switch Array with Full Broadcast Capability
Authors: Bogert G. A.
Published: February 2023

Recently, Tr:LiNbO3 optical switch arrays have received significant attention with several NxN arrays reported in the past year [1,2,3]. While there has been considerable improvement in the performance and complexity of the arrays, all have been of the crossbar architecture. The crossbar architecture, while providing nonblocking point-to-point operation, does not allow for the broadcast function, a highly desirable characteristic for an array.
System Considerations for the Lithium Morate Photonic Switching Technology
Authors: Payne W. A. , Hinton H. S.
Published: February 2023

This paper discusses several system areas that require development prior to the successful implementation of the lithium niobate technology for photonic switching. The paper first describes several components required in a photonic switching system as well as the status of their development. It then discusses the system architectural areas that either require development or resolution. The final area discussed is the need for viable applications for photonic switching.
Analytic Expressions for Switching Irradiances of Bistable and Multistable Nonlinear Fabry–Perots
Authors: Thienpont H. , Van de Voorde I. , Verbesselt I. , Veretennicoff I.
Published: February 2023

A procedure is developed to obtain analytic expressions for the switching irradiances characterizing the bistable and the multistable behaviour of a non linear Fabry-Perot, filled with a lossless, Kerr-type medium. Based on approximating the Airy-curve with a parabola near the commutation points, this procedure brings forward a set of analytic expressions allowing for a fast and easy determination of both up- and downswitching irradiances. These expressions are derived and the results are highlighted because of their accuracy, conciseness and ease of applicability. Finally a few practical examples are shown and some applications are discussed.
New Direction in Photonic Switching: A Collapsed-Network Space-Division Switching Architecture
Authors: Prucnal Paul R. , Perrier Philippe A.
Published: February 2023

A novel photonic switching architecture is proposed which can provide extremely high dimensionality. The proposed architecture, which resembles a collapsed network, avoids the difficulties associated with the use of optical crosspoints. This is accomplished by providing a dedicated path for all input- and output-port connections on a common transmission medium. This eliminates the restrictions imposed by 2x2 switching elements in classical space-division switching architectures.
Efficient Clock Distribution in a High-Speed Time-Multiplexed-Switched Optical Network
Authors: Korotky S. K. , Azizi A.
Published: February 2023

We demonstrate an efficient method for clock distribution in time-multiplexed-switched optical local area networks. The local clock of a 4 Gb/s terminal on an experimental network is synchronized to the switch master clock located 5 km from the terminal.
Frequency-Division-Multiplex Coherent Optical Switch Experiment with Monolithic Tunable Lasers Covering a 1000-GHz Range
Authors: Eng K. Y. , Santoro M. , Koch T. L. , Snell W. W. , Stone J.
Published: February 2023

Considerable progress has been made in coherent optics for local network applications whereby a star coupler is used to combine various Frequency-Division-Multiplex (FDM) channels from the inbound lines for broadcasting onto each of the outbound lines [1-4]. Many practical challenges in such FDM networks (e.g. synchronization, control of the FDM comb, polarization maintenance etc.) can be minimized when we shrink the entire network inside a "box" so as to build an optical switch capable of cross-connecting many high-speed circuits carried in multi-Gb/s fibers [5], We describe here results of an on-going experiment aimed at exploring the technical feasibility of this approach, and our laboratory demonstration is believed to be the first one done with monolithic tunable lasers covering 1,000 GHz at 700 Mb/s and with a novel tuned, balanced coherent receiver design, yielding a potential switch size as large as 125×125.
Polarization Independent GaAs/AlGaAs Electro-Optic Guided-Wave Directional Coupler Switch Using (111)-Oriented GaAs Substrate
Authors: Komatsu K. , Hamamoto K. , Sugimoto M. , Kohga Y. , Suzuki A.
Published: February 2023

The interest in guided-wave optical switches made of III-V semiconductor compounds for photonic switching application is growing, because of their large scale integration capability and their ability to be integrated with other semiconductor devices. Therefore, several kinds of optical switch, such as a carrier injection type switch[1], a gain guide type switch[2] and a directional coupler type switch[3], have been investigated. Among them, a GaAs/AlGaAs electro-optic directional coupler (EODC) is attractive, because of its low absorption loss at long wavelength region[4], fast switching speed, low electric power consumption and wavelength independent operation capability. Therefore, a GaAs/AlGaAs EODC is promising as a cross-point element in an integrated matrix switch. Actually, 4×4 GaAs/AlGaAs matrix switches with quite uniform device characteristics have already been realized[5] by the authors. However, all of reported semiconductor directional coupler switches, so far using electro-optic effect, have been polarization sensitive. Polarization independent semiconductor EODCs, compatible with standard single-mode fibers, are desired for practical use. Although some polarization independent LiNbO3 switches have been recently reported[6],[7], no attempt to realize polarization independent semiconductor EODC has been made yet.
Studies on a 128 Line Photonic Space Division Switching Network Using LiNb03 Switch Matrices and Optical Amplifiers
Authors: Burke C. , Fujiwara M. , Yamaguchi M. , Nishimoto H. , Honmou H.
Published: February 2023

Photonic space division (SD) switching systems are particularly promising and most practical for providing the necessary broad-band services for future telecommunication needs. A 32 line SD switching system employing polarization independent LiNbO3 8×8 switch matrices [1] has already been demonstrated for use in a Local-Area-Network [2]. Application expansion of such a switching system requires further increasing the line capacity to greater than 100 lines. Introducing semiconductor Traveling Wave Amplifiers (TWAs) to the switching network would be a very effective method for achieving such an increase [3]-[5].
All-Optical Control Circuits for Photonic Switching
Authors: Himeno Akira , Shimazu Yoshihiro
Published: February 2023

Future communication services will require intelligent and high-speed control circuits as well as broadband information switching equipment. For the switching equipment, optical switches, such as space-, time-, and frequency division switches, are attractive because of their inherently wide bandwidth and immunity to induction. For the control circuits, required functions fall into two categories, high-speed simple functions and low-speed intelligent functions. Optical new technologies will be demanded for the former functions, though electronics will play an important role for the latter as it does today.
Surface-Emitting Laser Logic
Authors: Olbright G. R. , Bryan R. P. , Brennan T. M. , Lear K. , Poirier G. E. , Fu W. S. , Jewell J. L. , Lee Y. H.
Published: February 2023

Here we describe our efforts to build an ideal optical switch based on the monolithic integration of a heterojunction phototransistor (HPT) with a vertical-cavity surface-emitting laser (VCSEL) diode. To date we have demonstrated high optical gain (> 20 overall, > 200 differential) with the discrete components connected in series. Our devices are ideally suited for parallel optical signal processing which is currently regarded as the most promising research area for achieving significant increases in computational throughput relative to purely electronic based information processing. Parallel optical processing has been severely hampered by the lack of several basic "building block" devices such as optical switching devices that exhibit low-switching energy, high optical gain (fanout capability) and high contrast. Devices should be: easy to fabricate (use of self-aligned VLSI technology), microscopic in size, and readily integrable with other optoelectronic components without being adversely affected by external optical feedback.
S-SEED-based photonic switching network demonstration
Authors: McCormick F. B. , Tooley F. A. P. , Cloonan T. J. , Brubaker J. L. , Lentine A. L. , Morrison R. L. , Walker S. L. , Hinterlong S. J. , Herron. M. J.
Published: February 2023

The demonstration of a digital, free-space switching fabric will be described[l,2]. It consists of three cascaded 16x8 arrays of Symmetric Self Electro-Optic Effect devices (S-SEEDs)[3]. The first array of bistable devices implement the input interface. The other two arrays operate as two-input logic gates with a fan-out of two. Crossover interconnects are implemented between the arrays[4]. The correct operation of the circuit results in the implementation of an array of 32 independent 2x2 nodes.
Mobility-lifetime product of photoexcited electrons in GaAs
Authors: Valley George C. , Rajbenbach H. , von Bardeleben H.J.
Published: February 2023

Application of large DC and AC fields to undoped semi-insulating GaAs to enhance its photorefractive performance leads to improvement compared to no applied field, but the improvement is not nearly as large as predicted theoretically when zero-field values of the mobility-lifetime product are used in the calculations. For example, Fig. 1 shows the gain coefficient as a function of grating period when an AC electric field is applied to the sample.1 The dashed lines are theoretical predictions based on a mobility of 5000 cm2/V-sec (from the Hall mobility of an adjacent sample) and a carrier lifetime of 30 nanoseconds (based on literature values for the recombination cross section of electrons to the EL2* level2). The solid lines are based on a mobility lifetime product four orders of magnitude smaller.
Kinetics of induced nanosecond absorption in photorefractive InP:Fe
Authors: Halter P.U. , Fabre J.C. , Roosen G.
Published: February 2023

For understanding and optimization of the photo refractive gain it is important to know the basic parameters of photo-ionization and recombination processes. In the nanosecond regime the pulse energies required for maximum coupling gain in semiconductors easily reach the limit for saturation of the deep centers. especially if one of the recombination times is larger than the pulse duration. In that case, induced absorption (or bleaching) will appear due to a redistribution of the population of the different levels of the deep center and counterbalance photorefractive amplification. The present simultaneous study of the kinetics of the induced absorption and the photocurrent in an InP:Fe sample reveals a number of interesting parameters like electron and hole recombination times, ionization cross sections and Fe2+/Fe3+ concentrations.
Direct measurements of charge carrier mobilities in photorefractive sillenite crystals
Authors: Pauliat G. , Villing A. , Launay J.C. , Roosen G.
Published: February 2023

The charge carrier mobility*recombination time product (μτ) is an important photorefractive parameter. In the band transport model [1], this product is one of the three crystal parameters (with Na the deep trap density and τdi the dielectric recombination time) which govern the kinetics of the photorefractive effect. Usual photorefractive measurements of μτ are lengthy and give uncertain results for some samples in which the band transport model is not detained enough to completly describe the photorefractive effect.
Characterization of Cooper Doped BGO Application to Double Phase Conjugate Mirror
Authors: Wolffer N. , Gravey P. , Moisan J.Y. , Laulan C. , Launay J.C.
Published: February 2023

In order to improve the properties of photorefractive (PR) sillenite crystals, different dopants are currently being investigated. In this paper, we present some of the characteristics of two cooper doped Bi12GeO20 (BGO) crystals.
Photoluminescence Spectroscopy of Doped and Undoped BaTiO3
Authors: Mullen Ruth Ann , Schumacher Kimberly L. , Wechsler Barry , Klein Marvin B.
Published: February 2023

Despite the many important potential applications for photorefractive BaTiO31, the precise nature and the depth of the photorefractive trapping centers has yet to be positively identified. In one study2, a correlation was noted between the iron concentration as measured with EPR, the photorefractive trap density determined by two-beam coupling versus grating wavevector measurements, and the optical absorption coefficient. This tentatively identified iron as the photorefractive center in commercially-grown, nominally undoped crystals. More recently, high photorefractive gains were reported in nominally iron-free BaTiO3 crystals3, and evidence was presented3,4 that, in purposely iron-doped crystals, the most common valence states for iron are Fe+3 and Fe+4.
On the Temperature-Dependent Photorefractive Effects in BaTiO3
Authors: Blanchard D.M. , Brost G.A. , Motes R.A.
Published: February 2023

In a recent letter Rytz et al[1] reported results of two-wave mixing experiments performed on BaTiO3 crystals in the temperature range between 20° and 120°C. They observed a large decrease in the density of empty traps as well as a significant decrease in the response time at elevated temperatures. The physical mechanism for the observed effects was not well understood. In this paper we show that the temperature variation in the empty trap concentration is accounted for by secondary photorefractive centers and discuss the possible influence of these traps on the hole mobility.
Optic and spectroscopic investigation in photorefractive BaTiO3 crystals
Authors: Maillard A. , Jullien P.
Published: February 2023

To characterize BaTiO3 by optical measurements it is necessary to know spectroscopic results from the same sample. We propose datas from EPR, Mass spectroscopy, absorption and conclude about the diversity of samples.
Light Diffraction by Holographic Gratings in Optically Active Photorefractive Piezocrystals
Authors: Mandel A.E. , Shandarov S.M. , Shepelevich V.V.
Published: February 2023

A number of cubic photorefractive crystals (CPC) have piezoelectric properties and natural gyrotropy simultaneously. It is known 1−3 that while recording holographic gratings (HG) in photorefractive piezocrystals there has been existed the secondary contribution to the disturbances of optical properties of the medium. It depends on joint action of piezoelectric and photoelastic effects. The secondary contribution can be taken into account by introducing effective electrooptic constants r'mnp 1−3. The account of gyrotropic properties of CPC in terms of approximation of coupled waves for arbitrary orientation of the grating vector k in the plane (110) has been carried out in the paper4.
Mode Degradation by Photorefractive Damage in Planar Optical Waveguides
Authors: Jariego F. J. , Agulló-Lóoez F.
Published: February 2023

Electrooptic materials, particularly LiNbO3, are used to fabricate optical waveguides and a variety of integrated optics devices1. However, the performance of this devices is hampered by the light-induced change in refractive index which leads to mode degradation. This damage or photorefractive effect (PRE) has been extensively investigated2 for LiNbO3 and a number of experiments have dealt with mode degradation in waveguides3,4,5. However, the theoretical description of these phenomena is in a very preliminary and insatisfactory stage.
The Properties of Phase-Conjugate In Photorefractive SBN:Cu Crystal
Authors: Xu Keibin , Yu Youlong , Xu Haiying , Yuan Yang , Chen Huanchu , Zhang Qinglun , Xu Yuhuan , Zhu Derui
Published: February 2023

The phase-conjugate reflectivities are measured relating with the incident angle in SBN:Cu crystal. The signal intensity dependence of the crystal response time and phase-conjugate reflectivity is given. The decay time of phase-conjugate is proved varying with the applied electric field.
Planar Hologram Arrays in Photorefractive Waveguides in LiNbO3
Authors: Itkin I.I. , Shandarov V.M. , Shandarov E.S. , Shandarov S. M.
Published: February 2023

The dynamics of hologram recording in optical waveguides on the basis of photorefractive crystals is determined by a number of factors, and among them there are types and indices of interacting modes [1-3], correlation between the periods of the array and thickness of the waveguide layer h, orientation of the substrate and array vector
K→ relative to the crystallophysic axes [4]. The results of investigations of planar hologram array recording by the waveguide TE-modes in the structures on the basis of lithium niobate have been cited in the given report.
An Analytic Expression for the Photorefractive Two Beam Coupling Response Time
Authors: Vachss Frederick
Published: February 2023

Among the most widely used properties of photorefractive materials is their ability to couple energy between two beams overlapping within the medium. This property allows for a weak information carrying beam to be amplified at the expense of a strong pump beam and thus provides a fundamental building block in a variety of applications of practical interest including optical interconnection and computing, image processing and laser hardening. In engineering such optical systems involving a photorefractive amplifier, accurately predicting the speed at which the amplifier will respond becomes a necessary facet of system design. As a result, the temporal response of the photorefractive effect has been the subject of extensive investigation. In the absence of two beam coupling, these investigations have resulted in explicit expressions for the photorefractive response time as a function of various relevant material and environmental parameters. While similar expressions valid when beam coupling is present have not yet been presented, and indeed are the subject of this paper, substantial progress toward their development has been made previously by other workers.
Nonequilibrium Charge Transfer and other Low-Temperature Photorefractive Effects
Authors: Nolte D. D. , Glass A. M.
Published: February 2023

A dramatic quenching of the photorefractive effect at low temperatures has been observed. We will also demonstrate that optical quenching in GaAs during four-wave mixing produces a direct modulation of the Fermi level in the material.
Time Resolved Investigation of Photorefractive Gratings in KNbO3
Authors: Biaggio I. , Zgonik M. , Günter P.
Published: February 2023

Electrochemical reduction1 leads to faster recording and decay times in KNbO3 crystals. In the simplest model the only photorefractive centers considered are iron impurities in two valence states Fe2+ and Fe3+. Reduction of the crystals reduces a great majority of these impurities to the Fe2+ state and increases the electrical conductivity. In this work we study gratings written with short pulses in such crystals.
Investigation of photorefractive gratings induced in BSO crystals by picosecond pulses
Authors: Brotons E. , Pauliat G. , Roosen G.
Published: February 2023

Sillenites crystals are the subject of intense investigations in view of either studying their basic properties or realizing devices.
Transient Photorefractive Effect in Graded Gap Superlattices
Authors: Ralph Stephen E. , Capasso Federico , Malik Roger J.
Published: February 2023

We report a new type of photorefractive effect which does not rely on traps, requires only a single illumination beam and is inherently fast The effect is efficient enough to cause significant polarization rotation of a probe beam via the electro-optic effect, using only a short (2µm) interaction length. Furthermore, the temporal response can be easily controlled by changing either the intrinsic or photo-induced carrier density. The effect can also be used to examine the transport of free carriers in graded gap structures.
Thin Epitaxial Films of Photorefractive Materials
Authors: Gower M C , Vainos N
Published: February 2023

Provided they can be satisfactorily fabricated, the use of thin films of photorefractive material as four wave mixing media for real time holographic application is an extremely attractive alternative to the use of the bulk crystal. For example, because guided wave intensities in the film can be very high-even when using lowered cw laser sources, the response time for holographic recording can be very fast. For example, ~100 mW of power coupled in a ~1 cm wide 1µm thick stripe of BaTiO3 film should reduce the response time from ~1 sec at 100 mW/cm2 in the bulk crystal to ~100 µsec in the film. Furthermore, with thin photorefractive films large area real time phase conjugate mirror operation with low powered laser sources can be contemplated.
UV-Induced Refractive Index Changes in Germanosilicate Fibres
Authors: Hand D.P. , Russell P.St.J. , Wells P.J.
Published: February 2023

Photorefractivity in germanosilicate fibres was first reported by Hill and co-workers over a decade ago1. They were able to produce holographic gratings 60 cm long by interfering counterpropagating modes at 488 and 514.5 nm. Further measurements by Lam and Garside2 indicated that reflection efficiencies approached 100% for interaction lengths of l-2cm implying refractive index modulations of the order of 10-5. They were unable to estimate the spectral variation of the index change Δn(λ) because the reflection band was restricted to the recording wavelength. It is clear that, for distributed reflectors at communications wavelengths, the effect is only useful if i) a substantial index change, extends out to beyond 1 μm and ii) a satisfactory method of side-writing gratings can be found.
Theoretical Modelling of the Fixing and Developing of Holographic Grtings in LiNbO3
Authors: Carrascosa M. , Agulló-López. F.
Published: February 2023

Two wave mixing can be used (1) to write volume phase holograms and therefore, store information in photorefractive materials such as LiNbO3. However, the written holographic gratings suffer from light-induced erasure leading to loss of stored information during read-out. To avoid unwanted optical erasure, one possibility is to stabilize the grating by thermal fixing, which has been investigated in detail for LiNbO3 (2–3). More recently, thermal fixing in other materials is being studied (4), although the physical mechanism are less understood.
Optical Implementation of Perceptrons Using Photorefractive Media
Authors: Hong John H. , Campbell Scott , Yeh Pochi
Published: February 2023

While volume holograms offer a powerful means for providing interconnections for many information processing tasks, the adaptable interconnection capability necessary for implementing learning algorithms for neural networks finds an almost ideal realization in photorefractive crystals. The dynamic holograms in which gratings are built up in real time without the need for separate development cycles make them appealing for neural implementations [1-3]. This, coupled with the highly dense information storage capability that is inherent in volume holograms (e.g.,~1012 interconnections in ~1 cm3 [4]) make photorefractive implementations unique among many neural implementation technologies.
Reconfigurable Optical Interconnection Using Photorefractive Media
Authors: Chiou Arthur , Yeh Pochi
Published: February 2023

Optical interconnection between VLSI circuits, computing chips or boards plays an essential role on parallel computing. Such an approach utilizes the fast switching speed of electronics and the massive parallelism and wide bandwidth of optics for communication and provides the potential of achieving extremely high speed [1,2,3]. A generalized optical crossbar switch [4] which can provide a reconfigurable and arbitrary interconnection between an array of N lasers and an array of N detectors can be implemented using a parallel matrix-vector multiplication scheme [5]. The N2 parallelism of this scheme is accompanied with an intrinsic fan-out energy loss [6]. The fan-out leads to an energy efficiency of 1/N.
Angular selectivity of multibeam coupling in photorefractive BaTiO3
Authors: Klees L. , Denz C. , Tschudi T.
Published: February 2023

The angular dependence of simultaneous multibeam coupling in photorefractive BaTiO3 is studied theoretically and experimentally.

It is found out that the amount of gain that each signal receives depends strongly on the angular configuration of the incoming beams relative to the c-axis and relative to each other. The competitive interaction of. the gratings from different signals causes some signals to receive larger energy increments as others. Moreover, crosstalk between the signals can be modified by changing the incoming angles.
Energy Transfer between Speckle-Waves in Photorefractive Crystals
Authors: Mamaev A.V. , Shkunov V.V.
Published: February 2023

Theoretical and experimental results on two-waves mixing with speckle-beams in photorefractive crystals are presented.
Semilinear Double Phase Conjugate Mirror
Authors: He Qi-Chi , Duthie J. Graeme
Published: February 2023

Photorefractive double phase conjugation has been an interesting subject in recent years [1] [2] [3]. The interaction process can self-generate a pair of phase conjugate replicas from two mutually incoherent beams without spatial and temporal modulation cross talks [1] [4]. This unique characteristic has drawn a great interest in many potential applications such as optical communication, information processing, laser beam steering and phase-locking etc. In this work we introduce another configuration of double phase conjugation: Semilinear Double Phase Conjugate Mirror (SDPCM). Experimental studies show that this configuration has high phase conjugate reflectivity, wide acceptence angle, good phase conjugate fidelity and resonably fast response time. Over 250% phase conjugate reflectivity is obtained in this single-crystal passive phase conjugation device.
Phase-Conjugate Fiber-Optic Gyros
Authors: McMichael Ian , Christian Bill , Beckwith Paul , Khoshnevisan Monte , Yeh Pochi
Published: February 2023

Phase-conjugate fiber-optic gyros (PCFOG’s) use phase conjugation to compensate for reciprocal phase changes due to thermal and mechanical effects on the fiber, while at the same time. allowing for the measurement of the nonreciprocal phase shift produced by rotation.1,2 Where the best standard fiber-optic gyros require polarization-preserving fibers and couplers to avoid polarization scrambling that is a source of noise and signal fading, the PCFOG can avoid this problem by using polarization-preserving phase conjugation.3 This has the advantage of allowing for the use of inexpensive nonpolarization preserving, and even multimode fibers and components.3-5 Our first objective was to demonstrate that the PCFOG is sensitive to the nonreciprocal phase shift produced by the Sagnac effect and can be used to sense rotation. A proof of concept experiment was set up for this objective using an externally-pumped crystal of barium titanate as the phase conjugator. This experiment, reported in Ref. 6, provided the first demonstration of rotation sensing with a PCFOG. In this proof of concept demonstration the length of the fiber-optic coil, and therefore the sensitivity of the gyro, was limited by the coherence length of the laser. To solve this problem we set up a PCFOG consisting of a Michelson interferometer in which the light beams from two arms travel as clockwise and counterclokwise beams respectively, in the same fiber optic coil and reflect from the same self-pumped phase-conjugator. We reported the demonstration of rotation sensing with this PCFOG in Ref. 7. Again, since phase conjugation can correct for modal scrambling, a PCFOG can use multimode fibers. However, complete correction of modal scrambling requires a polarization-preserving conjugator,5 and the corresponding experimental setup of a PCFOG is complicated. To solve this problem we set up a PCFOG using a multimode fiber coil, a nonpolarization-preserving conjugator,4 and a spatial filter to discriminate against the portion of the light reflected by the conjugator that does not correct for modal scrambling. This experiment, reported in Ref. 8, provided the first demonstration of rotation sensing with a PCFOG using multimode fiber.
Photorefractive Crystal Fe:KNbO3 and High Efficiency Self-pumping Phase Conjugation Mirror
Authors: Shen Dezhong , Jiang Daya , Tong Xiaolin
Published: February 2023

Potassium niobate (KNbO3) crystal is not only a ferroelectric with strong nonlinear optical properties, but also a very good electro-optical material. Its electro-optical coefficient Γ42=380pm/v, and related dielectric constant ε and refractive index n are 240 and 2.3 respectively, therefore the photorefractive figure of merit Q (=n3 Γ42/ε) =19.3 (pm/v) [1] is the largest one comparing with BaTiO3, SBN, BSO, LiNbO3, LiTaO3 and GaAs.
Two Wave Mixing Using Dual Frequency Signals in BaTiO3 - Application to the Amplification of Microwave Signals
Authors: Dolfi D. , Forestier B. , Loiseaux B. , Rajbenbach H. , Huignard J.P.
Published: February 2023

We analyze and experimentally demonstrate a new two wave mixing interaction using dual frequency signal beams and its application to the amplification of microwave signals. A differential gain γΔ = 17 is obtained in BaTiO3 when the signal beam frequencies are separated by fO = 2.2 GHz.
Phase conjugate interferometric measurement of thin film parameters
Authors: Cronin-Golomb M. , Shamir J.
Published: February 2023

We describe here a self-aligning interferometric device for the measurement of the thickness, refractive index and absorption coefficient of optical thin films.
Contrast Manipulation and Controllable Spatial Filtering Via Photorefractive Four Wave Mixing and Two-Beam Coupling
Authors: Hussain G. , Eason R.W. , Khoury J.A.
Published: February 2023

Spatial filtering, which relies on the insertion of masks, slits or other objects such as stops in the Fourier transform plane of an optical imaging system, is a well established technique for optical image processing, These conventional methods, however, suffer from serious drawbacks such as the possibility of updating or renewing these Fourier masks at the speeds required for real-time processing.
Photorefractive effects in the organic crystal 2-cyclooctyIamino-5-nitropyridine (COANP) doped with 7,7,8,8-tetracyanochinodimethane (TCNQ)
Authors: Sutter K. , Hulliger J. , Günter P.
Published: February 2023

Photorefractive effects (due to electro-optic index change driven by photoinduced space-charge fields) have been found in a wide range of inorganic materials such as LiNbO3, KNbO3, Bi12SiO20, BaTiO3, GaAs, InP:Fe and others. To our knowledge, no such effects have been reported yet for an organic crystal. In this paper we report the observation of photoinduced gratings in an electro-optic molecular crystal which has been intentionally doped to induce photorefractive properties.
Photorefractive Effects in Ferromagnetic Semiconductors with Superlattice Formed by Coherent Light Beams
Authors: Semchuk A. Yu.
Published: February 2023

Let us consider a wide-gap donor-type a ferromagnetic semiconductor (FMSC) with mean carrier density nOin the spin wave temperature range placed in an external constant electric field
F→O//OZ, magnetic field
H→O//F→O and variable weak magnetic field
h→/H→O. Its face surface is subjected to several coherent light beams (CLBs), whose frequencies satisfe the inequality
ε¯≪ℏω≪ε
g
(ε
g
is the energy-gap width). In this case, as a result of the interference phenomena, there appear new regularities in the character of the high-frequency CLB field influence on free carriers and magnons. Thus, for example, the spatial modulation of collision integrals and high-frequency light waves pressure force on electrons leads to the formation of superlattices of the carrier density, electron and magnon temperatures, electric field strength, and magnetization intensity in the system of non-equilibrium electrons and magnons of FMSC.