Hard amorphous hydrogenated carbon (a-C:H) films are tested as a potential active write-once medium for optical data storage. The recording mechanism is based on blister (bubble) formation due to film/substrate adhesion failure. Using an Ar+ laser beam the micron-sized bubbles with a high optical contrast were created in a-C:H/glass system.

Photochromic films with a natural protein bacteriorhodopsin as a light-sensitive material have been known. Information storage in such films is no more than one minute. We have developed films in which photodecomposition of the protein-chromophore complex takes place during photoinduced hydroxylaminolysis. The spectral product is retinaloxime with the absorption band maximum at 380 nm. The irreversibility of retinaloxime formation permits this process to be used for production of memory systems based on the write-once optical records with storage times of more than one year. The diffraction efficiency in these films reached 0.2 - 0.3%, the lifetime of grating being equal to several days. The photosensitivity depended on the history of the sample. The films permit simultaneous recording and readout of both dynamic and so-called `semiconstant' holograms in the same region of the sample.

Refractive index variation due to photothermoinduced crystallization of polychromatic glass has been found. This effect is used for 3-D phase hologram recording. Optical properties of holograms are stable in the wide spectral and temperature range. Holograms have high diffraction efficiency and angle selectivity.

A brief review of the original results of investigations and development of light-sensitive organic materials for optical discs is presented. The photopolymers may be used as substrate materials, clear protective coatings of optical discs, and for their replication. Photoanisotropic organic materials are used as light-sensitive media for recording optical information.

The possibility of data recording in alkaline-earth phosphors doped with rare-earth ions is demonstrated. The results of experimental studies of optical, electronic, and structural properties of SrS and CaS alkaline-earth sulfides activated by Eu (Ce) and Sm ions are reported.

The influence of duration of laser radiation impulses on the mechanisms of thermomagnetic recording on thin amorphous films of alloys with perpendicular anisotropy is considered. Examples of these alloys are TbFe, DyFe, TbCo, and DyCo, which currently are under investigation for recording applications. For duration of impulses (tau) >= 10-7s the process of stable domain structures formation is considered under the inhomogeneous heating in the presence of weak external magnetic field. For (tau) -8s it is shown that at a slight heating of the exposed area large pressures are developed in the film. Optical recording with higher energy sensitivity than in the thermomagnetic method is realized in these films.

In this work the latest achievements in the molecular design of high-resolution and high- photosensitive photothermoplastic (PTP) heterostructures, the fundamental limitations of real- time information recording and new devices for information registering, and optical processing storage and protection on the base of the PTP heterostructures are considered.

In this paper the results of the investigation of the image formation process on photothermoplastic recording media with a photosensitive layer of arsenic chalcogenides are reported. It is shown that photoresponse peculiarities of these materials allow different effects to be used for optical information recording. The results of the investigation of the reciprocity law and image characteristics, obtained in a still mode of recording, are given. The great possibilities of a prime raster formation on a thermoplastic layer surface for sensitometric characteristics improvement are shown.

Optical interconnections in optoelectronic integrated circuits are considered a promising way to solve the multiple connection problem for neural networks. Three-dimensional interconnections between integrated circuits with optical inputs and outputs are proposed, with optical modulators as output elements and multilayer integrated optics waveguide blocks as interconnections. Experimental results on waveguide technology and characteristics, as well as on multiple quantum well modulators, are shown.

Optical interconnections employing waveguides and total internal reflection holograms as a basic element are discussed. Methods of waveguide holography (WGH) allows the technology of VLSI systems to be matched with the optical interconnection conception. It is shown that WGH has an extremely high efficiency, it forms high resolution and wide view image, and it permits the signal-to-noise ratio to be increased.

The problem of spatial modulated light scattering by periodical phase grating with arbitrary modulation level and grating period is considered. A simple model for calculating transmission and reflection coefficients of the hologram grating is described. This approach is based on the Bloch mode analysis developed by Jariv and Yeh. The angular spectral parameters of the transmitted and reflected waves are derived analytically. An incident beam has a narrow angular spectrum located near the first Brillouin zone boundary. In this manner, the scattering parameters are determined for various hologram thicknesses and Brillouin zone sizes.

In this paper spatial characteristics of the light field in an interferometer containing two phase- conjugate mirrors and a nonabsorbing scatterer between them are considered using the scattering matrix formalism which covers a wide range of optical elements and completely takes into account all interference effects. The influence of the reflection coefficients of phase- conjugate mirrors, which are assumed to function without any spatial selection, on the quality of associative information reconstruction from a model reflection hologram is investigated. The related problems of spectral response functions determination as well as self-oscillation threshold and eigenmode frequencies calculation are solved for a simple model scatterer- semitransparent mirror.

Presented is a mathematical model of a multichannel electro-optical structure having T-shaped electrodes which allow calculation of principal parameters of multichannel light modulators: control voltage, contrast and channel crosstalk, transmittance, and transmittance nonuniformity. Numerical simulation results are given. The possibility of optimization of said parameters by varying electrode geometrical characteristics and light aperture is considered. Experimental results of investigations with calculation-based models are given.

The mathematical simulation of the switching processes in an MO linear light modulator with slitlike channels on high-coercive crystal of YFeO3 is carried out. For switching to be completed in 0.15 microsecond(s) it needs control current impulses of 0.8 - 1.2 A in amplitude and 0.1 microsecond(s) in duration that are experimentally confirmed. The realized laboratory model of the 32-channel controlled modulator for the system of information storage in the form of 1-D holograms admits the normal operation, provided switching rates are about 100 kbit/s in each channel. The higher rates of switching demand the use of special electrodes, crystal substrates, and cooling systems.

This paper discusses the architecture of an N X N optical spatial switch in which independent and arbitrary switching is realized using diffraction of light beams by a microhologram array (MA) programmed by two 1 X N acousto-optical elements. It is shown that a bacteriorhodopsin film can be used as a recording medium for MA. The throughput of each channel, being up to several Gbit/s the capacity of such a switch, can reach 104 X 104 channels, the time of an arbitrary switching being not more than 100 ms. Experimental results are given proving the possibility of implementing a switch having said characteristics.

Investigation results of the avalanche process in MRS-structure are given and the possibility of creating the multichannel avalanche photodetector based on such a structure for the one- dimensional hologram disk memory system is considered. The experimental sample of the photodetector has sensitivity approximately 104 A/W with wavelength (lambda) approximately equals 0.63 micrometers and response speed approximately 5 nsec.

Optically controlled bistability and signal competition are investigated theoretically and experimentally at an incoherent beam interaction in Fabry-Perot cavity containing two nonlinear elements: photochromic absorber on bacteriorhodopsin controlled by bleaching and coloring external beams and amplifier on organic dye pumped by periodic laser pulses.

Results of investigations on hologram recording on photothermoplastic tape carriers with Co2 laser heat development is considered. The high capacity holographic tape storage is described.

The peculiarities of one-dimensional hologram recording in three-dimensional media are considered. The optimum quantity of the hologram superposition is shown to depend on the photolayer thickness. Computer simulation results of the 34-channel recording-reproducing process of twice superposed one-dimensional holograms in the photolayer with the thickness 5 micrometers are presented, the ratio unit signal/zero signal being not less than 8 dB and the recoding density being nearly 108 bit/cm2. The experimental results of the recording investigations with the many-time superpositions (8 exposures) of one-dimensional holograms in the LiNbO3:Fe crystals with the effective thickness nearly 130 micrometers are presented.

The realistic estimations of principal parameters of the memory system using picosecond solitons in single-mode fibers are considered. The duration range of soliton digital information carriers, which make it possible to describe such pulses as the Schroedinger solitons, is defined. To estimate the lower bound of the memory system informative capabilities subject to two-level serial coding the model of pair interaction of the in-phase Schroedinger solitons have been analyzed. Application of semiconductor structures in some components for fiber soliton memory system is also discussed.

In this paper we consider problems of realizing an optical associative memory (OAM) to be used in high-performance computing and database systems computers. According to physical restrictions, the utmost parameters (information capacity, associative access time, and rate) of such a memory are evaluated. Presented is an analysis of various circuit engineering designs of OAM providing an enhancement in the information capacity up to 109 - 1010 bits, an associative access for the time of several nanoseconds with the information capacity being about 106 bits as well as multiport operations.

This paper presents an analysis of laser beam image recording on a metal-polymer film and an estimation of technical parameters of devices for the recording realization.

The point of view of neural networks as multilayered continuous autowave media is developed. Every small element of such a system is analogous in many properties to the neuron axon element and the connections between elements are of diffusion type. Digital electronic and optoelectronic media may be realized. The possibility of multilayered media to be used for pictures analysis and as associative memory is studied.

A short sketch of the cerebellar structure and function is presented. The list of most spectacular cerebellar features is given in an original interpretation framework. The results of analytic calculations and computer simulations of information processing in the cerebellum are presented. Blueprints of future research are briefly reviewed.

New devices and systems for optical computing on the basis of inphase optical elements are discussed. It is shown that the systems possess new qualities. They have versatile architecture and organization for data processing. The possibilities for designing nested structures and for entering arrays results in a number of internal connections and throughput, surpassing considerably those of the human brain.

Possibilities of time-delayed four wave mixing for implementation of associative memory systems in optics are theoretically investigated. Optical architectures based on this phenomenon are proposed. Advantages of the time-domain approach to associative memory implementation are discussed.

We consider some specific problems and phenomena of morphogenetic information storage, reproduction, and transfer including phantom leaf effect and field-induced morphogenetic translations between different taxonomic units. Several experimental results are presented and their explanation is given using a new approach to morphogenesis which combines some physical models of holographic associative memory and the mathematical formalism of Fermi- Pasta-Ulam recurrence for solitary waves in deoxyribonucleic acid.

The simplest spatially distributed neuromorphic dynamic system with large-scale spatio- temporal interaction is investigated. The model of the system is nonlinear optical ring cavity with field rotation around optical axis and signal time-delay in the two-dimensional feedback loop. The characteristics of rotary modes of the system are determined by the parameters of nonlocal spatio-temporal interconnections. The competition of rotary modes takes place like in neural networks of WTA type.

The concept of the construction of parallel digit neurocomputers with programmable architecture is proposed. The main results of practical realization of the presented concept are described and the prospects of its development are analyzed.

Artificial models of biological neural networks can learn from examples and generalize from what they learn, i.e., the learning in them is not rote. This distinctive capability makes them particularly attractive for use as neurocomputing structures in pattern recognition, control, and other complex signal processing tasks. Accordingly, considerable effort is being devoted to the incorporation of the neural paradigm in man-made systems. An important question, encountered in implementation of neurocomputers with adaptive learning ability in photonic hardware, is how to effectively realize programmable nonvolatile analog connection (synaptic) weights between neurons of the network (this incidentally is also an issue in electronic hardware implementation of neural networks). In this paper we consider electron trapping materials (ETMs), a class of infrared stimulable phosphors, as a possible candidate for achieving this goal. We will describe a moderate-sized photonic learning machine, presently under construction, in which the connection weights between neurons, stored in an ETM panel, can be incremented or decremented optically under computer control during learning then frozen in place by means of a novel electronic fixing scheme to form a nonvolatile associative memory. Unique features of several specialized components being used in the machine are also described.

A high-performance bipolar analogue optical neural network with flexible architecture has been designed. This is achieved by the use of an all-optical two-dimensional global interconnection system that uses holographic multiple imaging. The weight matrix and input planes of the neural network are determined by spatial light modulators (SLM). This facilitates learning in situ with direct learning techniques proposed. Simulated results from the optical analogue neural network are presented using image processing primitives as a demonstrator.

The high-order associative memory model is considered. Its optical implementation for bipolar vectors is proposed. A bit weighting method increasing the efficiency of the recognition of high-correlated patterns with the model order being decreased is proposed. Spatio-temporal and hetero-associative memory systems are considered. Numerical simulation results are given.

We demonstrate two optical neuro-processors based on coherent optics: An associative memory for word-break recognition and an on-line learning machine for multicategory classification. Finally, we show how both of the systems can be compacterized using recent devices including surface-emitting micro-laser arrays.

Optical implementation of two- and four-dimensional interconnection matrices (memory matrices) in the Hopfield-type neural network is carried out by using persistent spectral hole burning (PSHB) media. The capability of the present optical scheme to correct errors in the input image is demonstrated. The technique of photoburning of persistent spectral holes provides new parallel-accessible degrees of freedom that can be used for ultrafast optical processing. A holographic `monochromator' is proposed for high-resolution parallel detection of a large number of frequency components.

Some very recent research results in Japan on optical neural networks are reviewed. Relevant activities are briefly introduced.

We applied a learning network to the image processing of human cornea endothelial micrograms. Our neural model is a feed-forward network with interconnections between units constrained to be locally space-invariant to perform space-invariant processing. The network is trained by the error back propagation with some small parts of micrograms and their cell membrane images which are outline drawing made by hand. After training, the network showed good performance with unexpenenced micrograms. The final membrane images were obtained after additional processing by a conventional digital filter that is based on mathematical morphology and linear filtering.

The evolution state of information processing optical facilities and supercomputer architecture trends are examined. The block diagram of supercomputer on the basis of new architectural principles of construction is considered. The requirements to the high-capacity associative memory and wide-format, wide-band buffer-switch for such a supercomputer are formulated. It is shown that optical processing principles are preferable for creation of such devices.

It is common to say that optics offer advantages in realizing the parallelism, massive interconnectivity, and plasticity required in the design and construction of large scale neurocomputers. This suitability is discussed in the case of stochastic neural nets such as those implementing the simulated annealing algorithm and the Boltzmann Machine. An optoelectronic random number generator is proposed. It is based on speckle properties and allows the design of a small stochastic unit on silicon. Experimental results of probabilistic updating are given.

Analog and digital processors, based on fiber-optic logic elements are presented. It is shown that, despite long signal delays in logic elements, the maximum computing rate of fiber-optic processors is limited mainly by the bandwidth of basic elements.

A new concept of wideband spectrum analyzer taking into account the influence of technical parameters of two-dimensional raster scanning system on the analysis accuracy is described. The principal parameters 1imiting the dynamic range of analyzer are determined. The problems of the semiconductor lasers using as input modulator are considered.