To our knowledge we report the first fabrication of vacuum deposited thin film interferometers with an intermediate layer doped by quantum-confined semiconductor microcrystallites. These filters demonstrate new spectral and optical properties in addition to those typical for samples deposited by conventional thermal evaporation, and, in particular, high-speed optical switching with picosecond on/off time.

the soliton generation and trapping in nonlinear waveguide can be used to implement ultrafast, all-optical switches. In this paper, the phenomenon of the soliton emission from a nonlinear interface of a symmetrical waveguide and of the soliton trapping are analyzed by simulations performed using the beam propagation method. We show the correlation between the input optical power and the length at which the soliton generation occurs, along the propagation direction of the single-mode nonlinear waveguide. Based on these principles, new all-optical switching elements and logical gates can be designed, which exhibit many important advantages on the classical electro-optical devices.

Laser-induced transient gratings generated by picosecond pulses at 1.064 micrometers in GaAs and CdTe samples were used to diffract a picosecond probe pulse in the degenerate-four-wave- mixing geometry. Pulse and probe experiments performed using the same experimental set-up allowed us to measure the free-carrier lifetime. The ambipolar diffusion coefficient D was then determined by using only one laser-material geometrical configuration. In semi-insulating GaAs:Cr and CdTe:W, gratings persisted for more than one nanosecond and could be partially erased using a homogeneous picosecond pulse, the energy of which was one quarter of the writing energy. We present a model which explains these results.

We report measurements of optically induced refractive index changes and their saturation, in an InGaAs single quantum well, centered within a linear multiple quantum well waveguide Fabry-Perot resonator using diode laser sources. A small-signal nonlinear refractive cross- section (sigma) _n equals -8 X 10^-20 cm³ was deduced for probe wavelengths near the TE absorption edge, and (sigma) _n equals -4 X 10^-20 cm³, 100 nm from the bandedge.

Here we report on films of poly-3BCMU obtained with the Langmuir-Blodgett (LB) technique. The study is devoted to the spectroscopic analysis of multilayers, in view of the use in guided wave devices. A hybrid structure consisting of a LB film and a tapered ion exchanged waveguide is also presented and exploited to characterize the waveguiding properties of the organic film.

The high room temperature optical nonlinearity in heavily doped n-InP (n equals 10¹⁸ cm^-3) in the spectral region near the band edge has been investigated. The spectral and energy dependencies of the self-diffraction efficiency have been measured. The energy dependence of the transmission spectrum is also presented. The value of optical bleaching and the self-diffraction efficiency are shown to be strongly dependent on the wavelength of incident radiation. Preliminary estimations show that the nonlinear change of refractive index reaches the value of 0.002.

In this work an analysis of the nonlinear dynamics of an anisotropic dye laser with a saturable absorber has been carried out. Radiationless energy transfer in the absorber was taken into account. It has been shown that a specific type of auto-oscillation appears because of the interaction of the polarization modes caused by the radiationless energy transfer and by the anisotropy in the active medium induced by linearly polarized light pulse. This oscillation is characterized by a half-period shift of the radiation-density maxima of one polarization mode relative to the maxima of the other and is called an anti-symmetric oscillation. It has been noted that in the limit of the high energy migration rate these anti-symmetric oscillations disappear and the anisotropic laser with saturable absorber looks like an isotropic one.

Excitonic processes in CuCl nanospheres of mean radius ranging from 2 to 15 nm embedded in a glass matrix are investigated. Specific features resulting from quantum confinement are analyzed. Correlation between nonlinear-optical and photochemical changes have been revealed. The possibility of application of the same structure in the reversible and irreversible optical memory devices is discussed.

The e-h plasma stimulated luminescence line A₁ red-shifted (25 meV) due to band-gap renormalization is detected. The A₁ emission lasts 100 ps. This peculiarity evidenced that a switching time of 100 ps can be achieved.

The biexciton optical Stark-effect under resonant pumping between the exciton and biexciton levels is studied theoretically. The probabilities of biexciton two-photon absorption of a weak probe light and of one-photon biexciton-exciton transition are calculated. The optical Stark splitting manifests itself in two-photon biexciton absorption through two absorption peaks spaced 2 (Omega) apart. Omega is the Raby frequency. In the luminescence spectrum due to biexciton-exciton one-photon transition three luminescence maxima appear which are shifted with respect to the luminescence maximum in the case without pumping.

A new approach to the photonic switching based on inhomogeneous broadening of vibronic bands of the molecular system, induced by electrostatic interaction of dipole moments of the electronically excited molecules, has been proposed and analyzed.

The influence of the piezoelectric effect and photoelastic properties of cubic photorefractive crystals on simultaneous diffraction of two light waves on the holographic grating has been studied theoretically and experimentally. The possibilities of optimization of light intensity pumping-over have been investigated. It is shown that the piezoelectric effect and the photoelasticity greatly influence the conditions of optimization of the light intensity pumping- over.

A new mechanism of optical switching in dye doped nematics due to the excitation of hydrodynamical instabilities with a light controlled topology is presented for the first time. The optical bistability and self-diffraction effects due to intrinsic multiplicative feedback are observed as well. A single-mode cw laser beam was used in the experiment as a pump radiation.

The electric field effect on the free carrier absorption in semiconductors is considered on the basis of the quantum transport equation. In the quantum limit analyzed this effect is caused by the influence of the electric field on the electron-phonon interaction rather than by the hot carrier effect. Due to the dynamical origin this effect is characterized by the small response time of subpicosecond range.

Dynamics of optical nonlinearity are investigated experimentally in different time scales, from microsecond to nano-, pico-, and femtosecond domains. In addition Z-Scan measurements carried out the competition between permanent photodarkening and electronic nonlinearities in photoinduced absorption and refraction.

To merge the fields of polarization and nonlinear optics opens wide perspectives. The present work aims at investigating some of them. It is shown, on one hand, that if a nonlinear Fabry- Perot resonator filled with an optically isotropic material is addressed by an obliquely incident beam, the transmitted irradiance can switch from an up to a down state (or the reverse) if its polarization is properly modulated. If on the other hand the nonlinear cavity is filled with a linearly birefringent material, polarization optical bistability can occur, even at normal incidence. This polarization bistability can arise both by modulating the incident irradiance and by modulating the incident polarization. Optical bistability of the transmitted irradiance can also be induced by the modulation of the polarization of the incident beam. All these features provide new tools for parallel digital optical information processing.

The conditions of optical multistability in Fabry-Perot interferometer with a two-component resonant medium have been considered. The possibility for realization of the decaying and regular intensity pulsations of a light field has been shown and the conditions of such a realization have been analyzed.

The results are reported of a theoretical analysis of resonatorless optical bistability of the WFC-mirror on the basis of degenerate four-wave mixing in a resonant medium. The conditions set on the fields and parameters of a nonlinear layer leading to an effective nonstationary energy exchange and to the appearance of resonatorless optical bistability are discussed.

A theory of nonlinear resonators is applied to the analysis of the transmission characteristics of the Fabry-Perot etalon possessing linear anisotropic and nonlinear isotropic properties. Two models based on the nonlinearities of the resonant and nonresonant types are considered. Numerical analysis results indicating a possibility of arising polarization switching and bistability (in some cases multistability) under certain conditions are reduced.

We present asymmetric Fabry-Perot quantum well modulators which are overbalanced, so that at zero bias at the exciton wavelength reflectivity is high. As bias is applied and the quantum well absorption decreases the optical cavity balances, nulling reflection. By partially anti- reflection coating, at zero bias the optical cavity is balanced, so that the reflectivity is near zero, and increases with bias. Therefore we can integrate normally-on and normally-off high- contrast modulators by selective AR coating. With 10 volts bias, we obtain 11:1 contrast ratio for the normally-on devices and 8:1 for the normally-off devices. Possible applications include complementary output of optical logic gates.

The transverse nonlinear dynamics of an active system (laser with nonlinear saturable absorber in self-imaging cavity) are considered theoretically. The soliton-like light field structure formation as well as new effects of optical multistability originating from the transverse oscillation phase distribution are shown to be possible.

We report about measurements of optical bistability in hybrid AlAs/GaAs Bragg reflectors. We have estimated an optical switching energy of 0.1 fJmicrometers ^-2, a switching intensity of about 1 Wcm^-2, and an electro-optical modulation of 40% using a voltage swing of 60 V.

In this contribution we focus on thermally induced absorptive optical nonlinearities in II-VI semiconductors. We demonstrate an optical oscillator by introducing the sample into a hybrid ring resonator with long round trip time. In the case of only marginally bistable input-output characteristics (realized with a CdS single crystal) we get the following dynamical behavior: For high input intensities the oscillation period is a multiple of the delay time. When decreasing the input intensity relaxation oscillations that stabilize the system and prevent it from a transition to deterministic chaos become important. Additionally we investigate the spatiotemporal dynamics of the system if a large diameter holding beam is switched by a small and short light pulse. Here we find switching waves and metastable temperature profiles.

A GaAlAs Fabry-Perot device has been grown which displays thermally stable switching with a threshold of 1 mW and a contrast ratio of 10:1. With the help of theoretical analysis and experimentation we probe the issues which are relevant to using this class of device in a practical system context.

Optical and optoelectronic technologies have progressed sufficiently for the emergence of experimental demonstration of simple digital optical processors. For a significant contribution to the development of photonic switching and computation, a sufficiently complete set of components and sub-systems must be put alongside suitable architectures and algorithms. We review these connected factors and also report new results in power sources, modulators, and interconnections.

An asynchronous transfer mode (ATM) switching node consisting of semiconductor laser amplifier (SLA) gates and fiber loop optical buffers is investigated. The requirements on the SLA properties are investigated and BER-measurements are reported.

New all-optical high-bit-rate logic gates are proposed. They are based on the nonlinear propagation of bit pulses in a fiber loop interferometer with an integral asymmetrically located semiconductor laser amplifier. In view of cross-phase modulation effect the bit error rate as a function of input signals on-off ratio is calculated. Some estimations for a semiconductor laser amplifier are considered.

The present work lies within the scope of a general architecture analysis of all-optical cellular automaton involving optical nonlinearities. Here, we present all-optical subnanosecond invertor gates operating in transmission with picosecond pulses [30 ps full width at half height (FWHH)] through Cd_0.96Zn_0.04Te platelets (600 to 800 micrometers thick). The all-optical inversion is based on the induced absorption occurring in the spectral Urbach tail of the material. The temperature of the operation is 80 K. The input and output beams are at the same wavelength which is a critical condition for the cascadability of the device. The switch inversion energy is typically 3 - 5 pJ/micrometers ² around the wavelength (lambda) equals 782 - 783 nm at nitrogen temperature. We add an all-optical amplifier to the invertor in order to obtain for the gate an output level as strong as the input one and demonstrate the stability of the complete invertor-amplifier gate with a contrast between the high and low logical levels better than 2:1. Then, we use microlens arrays and demonstrate the simultaneous and parallel operations of several invertor gates.

A waveguide modulator for far-infrared light, based on the plasma resonance properties of a high density, thin electron sheet in semiconductors, is proposed. Parallel-coupled (uncoupled) waveguides can be uncoupled (coupled) by the presence of the electron gas.

A scheme for control of the transfer function of a nonlinear Fabry-Perot interferometer (F-P) using an independent light beam (optical pumping), tuned in frequency to the absorption band from the excited level of resonant medium, has been suggested. The possibility of switching operating modes of the interferometer (differential amplification, discriminator, optical bistability) has been shown.

A high-contrast optical switch-attenuator was developed on the basis of frustrated total internal reflection. High-attenuation coefficient (90 dB) and high switch speed have been achieved. Experimental characteristics of the optical switch are presented. Employment of the optical switch-attenuator in laser systems is also reported.

For the first time an all-optical fiber recirculating loop memory with a long storage time is demonstrated experimentally. Information is stored in the memory by recirculating optical pulses through a closed fiber loop employing all-optical repeaters operating via the stimulated Raman scattering (SRS) effect. The time during which information storage was observed was 10 min. The number of round trips through the loop was more than 100 million.

It is shown that very effective ERF SEED can be expected for II-VI semiconductor heterostructures with a homogeneous electroabsorptive narrow-gap layer. Some principles for realization of high contrast ERF SEED are presented.

Packet switching architectures which exploit the optical space switching stage are presented. Possible components for the implementation of the photonic space stage are InP devices. The paper discusses the basic principles of semiconductor optical switches and reviews the latest state of the art results on switches and monolithic space switching matrices.

Recently, the optical fiber networks have been developed and widely used. And now, the fiber to the home (FTTH) networks are planned. It is said that the electrical devices have many problems with applying an exchanger system which realizes the FTTH network. In this paper, we describe some application areas of photonic switching which seem like the breakthrough technologies against these problems. In these areas, we selected the distribution switch as an actual application of the photonic switching. Then, we propose a 3D-laminated optical circuit arrays switch (3D-LOCAS) which has functions to be used in the distribution exchanger system. We also are studying the switch size of 3D-LOCAS, and some problems in a real implementation. We describe some hints to solve the problems as well.

A high contrast, low voltage, symmetric self electro-optic effect device (S-SEED) is shown. A way of obtaining increased logical functionality from the S-SEED is proposed and the required functionality for performing optical packet header recognition and self-routing, in the context of an optical packet switch, is demonstrated. Device design and switch optimizations are also discussed.

Novel flexible self-routing optical interconnections for optical bus and optical link are proposed using far-field deflection of beam-scanning laser diodes. Basic experimental results using beam-scanning and fringe-shifting lasers are presented using spatially coded signals.

An optical beam shifter module consisting of liquid-crystal cells and a birefringent plate is investigated for a 1024-input-port switching network. High extinction ratio (> 20 dB) and low insertion loss (0.5 dB) are achieved by optimal device design. Precise optical alignment is obtained without any adjustment mechanism by using assembly baseplate and an optical assembly bench.

Holographic photorefractive gratings in optical waveguides with high photorefractive sensitivity on lithium niobate can be used for an information input in integrated-optical-vector- matrix multiplication devices. An influence of the Fe and Cu additional diffusion on the refractive index profile of LiNbO₃:Ti waveguides and their photorefractive properties has been investigated and a matrix component input in the device with acousto-optical vector component input are demonstrated.

This paper describes a four-channel optical switch module prototype for a reconfigurable optical interconnection network using a polarization-switched architecture and liquid crystal polarization control devices. Compact size and low insertion loss have been achieved by using integrated optical elements. The successful switching of 1 Gbps optical signals with little skew has been demonstrated.

An optical tristable device with optically controlled set and reset functions is developed for the first time. The device structure is a vertical and direct integration of four heterojunction phototransistors and a laser diode. Two HPTs (HPT-A and HPT-B) which are integrated just above the LD stripe are utilized to achieve the set operation, where the internal optical feedback from the LD to the HPTs takes an important role in the operation. On the other hand, an HPT (HPT-C or HPT-D) integrated slightly away from the position for the set operation is used to achieve the reset operation. The optical feedback from the LD to the HPT- A and the HPT-B is suppressed by the current bypass through the HPT-C connected to both ends of the LD.

We describe an ATM switching matrix based on wavelength encoding of cells for space switching. Taking advantage of the encoding scheme, the cells are buffered in a reduced set of fiber delay lines for contention resolution.

Some versions of a fast-acting multichannel polarization switch for use as a basic element of light-flux commutators are discussed. The feasibility of making a DKDP-based (10² X 10² channels and more) polarization switch with improved optical characteristics is demonstrated. In the case of operating the device near the crystal phase transition point at the control signal frequency of 10⁸ Hz, the contrast was not less than 200:1.

The paper presents theoretical analysis of parametrically coupled solitary states developing via codirectional acousto-optical interaction in anisotropic medium. A new fast modulator of the light based on that phenomenon is proposed. Some numerical estimations and feasibilities of such a device for applications are considered and discussed.

Holographic optical switching is demonstrated experimentally using a ferroelectric liquid crystal spatial light modulator. Each of 15 inputs can be switched to any of 23 output ports.

Here we present further development of methods for forming laser beams with uniform output amplitude distribution and present a new intracavity scheme of making them. The resonator we submit for consideration is based on Fourier and Talbot reproduction of the field and therefore is called a Talbot-Fourier Resonator.

Optically addressed liquid crystal light modulators containing photoconductive polymers were investigated in various recording regimes in projection or holographic schemes. Electrically controlled birefringence, optical activity, cholesteric-nematic phase transition, dynamic scattering, and scattering in polymer dispersed liquid crystals were used for light modulation. The best results obtained for the pulse recording holographic regime are the following: limiting resolution up to 1500 mm^-1, sensitivity 10^-8 J/cm²%, and diffraction efficiency 36%. All modulators can be used in optical information processing, holography, and so on.

In the present paper the refractive index N of ferromagnetic semiconductors (FMSC) with superlattices is calculated. It is shown that the presence of superlattice leads to the modulation of the light absorption coefficient of FMSC, which can be detected by the changes of the outgoing intensity of the sensing wave passed through FMSC crystal.

Loss-less 4 X 4 monolithic LD optical matrix switches have been made for the first time using InGaAs/GaAs strained single quantum-well GRIN-SCH wafers. The switching speed of this switch is 0.2 ns.

The results of investigations of avalanche photodetectors based on metal-resistive layer-silicon (MRLS) structures are presented. Consideration is given to a 10 X 10 MRLS photodetector array.

The degradation mechanism in quantum-well lasers has been elucidated.

This paper reviews silica glass waveguide planar lightwave circuit applications in photonic switching systems. Those include space division switching, and coherent optical signal processing in photonic frequency division switching and in asynchronous transfer mode switching.

The availability of optoelectronic components performing modulation and detection in the multigigahertz domain opens new avenues for optical transmission and processing of microwave signals. This paper briefly describes the state of the art in optoelectronic devices and reviews some system considerations, especially in the field of phased array antenna, that can warrant the introduction of optical technologies in radars.

A new cascaded-beam-shifter-type switching network (`diamond-type switch') based on 2 X 2 switch elements is proposed. An experimental 1024-input-256-output optical concentrator based on this switch structure is fabricated and demonstrated.

Because of optical loss variations through different connection paths in LiNbO₃ switch matrices, optical crosstalk in a photonic space division switching network is enhanced. This work theoretically investigates the power penalty due to optical crosstalk in a 128 line photonic space division switching network which employs loss compensating semiconductor amplifiers, and experimentally confirms the suppression of power penalty by employing an automatic power control (APC) scheme. Experiments have shown the successful operation of an APC system in keeping a constant optical power level throughout the system and the obtained negligible power penalty values obtained agree with a calculated model.

A scheme of an optical switch using a matrix of reprogrammable holograms is discussed. The light from each input channel is deflected to an output channel with a separate microhologram. The microholograms are recorded and overrecorded with two acousto-optical deflectors on a bacteriorhodopsin photo medium. The experiments have been carried out on a prototype with 20 X 20 channels. As shown, the capacity of such a switch can be increased up to 10⁴ X 10⁴.

The length of multistage architectures is a crucial design parameter. The compact architectures overcome this problem but raise several others: additional interconnects because of the separation of the switching arrays, and search for the best interconnection scheme.

A novel photonic switching network is reported which exclusively uses frequency switching stages and a shared-medium architecture. It provides point to point and point to multipoint connections without internal blocking. This proposal is compared with similar published networks which also are constructed either solely from frequency switching stages or from frequency and space switching stages. It is shown that the proposed switching network features fewer optical and opto-electronic components, and a highly regular architecture.