Optical Computing System Research Articles

An Optical Parallel Computing System with Electronic Feedback Circuits

A hybrid optical computing system having a parallel optical logic gate and electronic feedback circuits is proposed. With this system, various repeated parallel computations can be performed.

Experimental verification of parallel processing on a hybrid optical parallel array logic system

A hybrid digital optical computing system is constructed, a variation of the optical parallel array logic system (OPALS). The OPALS is a general-purpose digital optical computing system based on optical array logic, in which image coding and 2-D correlation are used to achieve parallel logical operations. In the constructed system, 2-D correlation for optical array logic is performed optically with a modified multireflective correlator; the other procedures in optical array logic are achieved by electronics including a TV feedback system. We have verified correct execution of programs written by optical array logic on the system. Although the processing speed of the system is still slow because of the sequential process in electronics, it can be drastically improved by replacing the sequential processing devices with parallel ones.

Optimization of Optical Components for Optical Computer Systems

We analyze several different methods of encoding and calculating optically thin periodic Fourier-transform binary phase gratings and multiple or continuous phase kinoforms for use as e.g. optical fan-out elements in all-optical computing systems. The construction of the gratings and kinoforms is equivalent to the phase retrieval problem which we formulate as a nonlinear optimization problem and solve using different numerical techniques. Typical gratings have very high diffraction efficiency (up to 95%) and high reconstruction accuracy.

Edge detection using optical symbolic substitution

Optical symbolic substitution architectures based on phase-only hologram and content-addressable memory are used for digital- optical edge detection. Accordingly, symbolic substitution rules for phase-only hologram based optical computing system and reduced minterms for content-addressable memory based optical computing system are determined and compared for the cases of three different operators.

Optical computing: introduction by the guest editors to the feature in the 1 May 1988 issue

The feature in the 1 May 1988 issue of Applied Optics includes a collection of papers originally presented at the 1987 Lake Tahoe Topical Meeting on Optical Computing. These papers emphasize digital optical computing systems, optical interconnects, and devices for optical computing, but analog optical processing is considered as well.

Spatial-Light-Modulator Interconnected Computers

Optical technologies perform the basic computer operations of communications, switching, and storage, have already proven superior to electronics for many communications situations, and advances in devices and materials suggest that optics are important for switching and storage. The spatial light modulator (SLM) is one of the devices expected to play an important role in optical computing. An SLM acts as a piece of film whose transmittance or reflectance may be varied spatially and temporally by electronic or optical means. Types of SLMs, the use of optics for computation and three proposed, as well as diverse optical computing systems that use SLMs for interconnections are described in this article.

Modular components for an optical array logic system

On the basis of modularization of an optical parallel array logic system (OPALS), a new concept of an optical digital computer is considered. The OPALS is a parallel digital optical computing system using optical array logic capable of executing parallel neighborhood logical operations, or cellular logic. Modularizing functional elements in the OPALS, stability, reliability, and flexibility of the system can be improved. Performance of the modularized OPALS is estimated.

Optical parallel logic gate using light modulators with the Pockels effect: applications to fundamental components for optical digital computing

This paper describes applications of an optical logicgate consisting of three spatial light modulators with the Pockels effect to fundamental components in an optical digital computing system. An SR flip-flop, data sampler, and decoder are proposed, and simple experimental results for these components are shown. The components are the most fundamental ones in a digital computing system and have many applications to various digital circuits..

Shift-connected SIMD array architectures for digital optical computing systems, with algorithms for numerical transforms and partial differential equations

The potential and promise of very high-performance spatial light modulators (SLMs) capable of performing logic operations have motivated the investigation of digital computing systems that possess many desirable attributes of optical systems, namely, massive parallelism, global communication at high bandwidths, high reliability, many useful degrees of freedom, robustness in the presence of defects, and simplicity. The parallelism of easily realizable optical single-instruction multiple-data (SIMD) arrays makes them a natural choice for implementation of highly structured algorithms for the numerical solution of multidimensional partial differential equations and the computation of fast numerical transforms. A system comprising several SLMs, an optical read/write memory, and a functional block to perform simple, space-invariant shifts on images has enough flexibility to implement the fastest known methods for partial differential equations (e.g., multilevel methods) as well as a wide variety of numerical transforms (e.g., FFT, Walsh-Hadamard transform, rapid transform) in two or more dimensions and using either fixed or floating-point arithmetic. Performance is projected at >109 floating-point operations/s using SLMs with 1000 × 1000 resolution operating at 1-MHz frame rates.

Optical parallel array logic system 2: A new system architecture without memory elements

An optical parallel array logic system—OPALS—is a new type of optical parallel digital computing system. The OPALS optically implements array logic in parallel using techniques of image coding and 2-D correlation for the coded image with a pointwise function called an operation kernel. The OPALS can execute any logical neighborhood operation for binary images in parallel. In this paper we present a new version of the OPALS that needs no memory elements. To construct this OPALS, we consider two useful techniques, i.e., an optical sequential logic technique and multiplex correlation based on wavelength multiplexing. Use of pipelined processing together with the wavelength multiplexing technique gives the promise of eliminating memory devices from the system. Consequently, the new version of the OPALS can be systematized with simpler architecture compared with that of the OPALS presented in the previous paper. Computer simulation verifies the appropriateness of operations of the new version of the OPALS.

Fabrication of arrays of GaAs optical bistable devices

Arrays of fast optical bistable devices (OBD’) hold excellent promise in the implementation of parallel optical computation systems. The fabrication of an array of 9×9 μm pixels of OBD’s on a GaAs/AlGaAs molecular beam epitaxial layer is reported here. The pixels were defined by reactive ion etching in a freon, helium, and oxygen gas mixture. The array, consisting of over 100×100 devices, formed good quality, uniform interferometers, exhibiting a single fringe in transmitted light. Gate recovery times were reduced by eliminating the top AlGaAs window and by etching 9×9 μm pixels in an array. Uniform arrays of such high quality optical gates or bistable devices could handle thousands of parallel channels at a rate of several gigahertz per channel.

Optical interconnections for digital processing: a noncoherent method

We describe the use of a lenslet-array-based device for interconnections in optical digital computing systems. This new device, the digital lenslet array processor, operates in polychromatic and spatially incoherent light, so it can use a wide spectrum of electro-optical light sources. An experimental example is presented.

Digital optical computing

This paper concerns binary digital computing systems in which the information-carrying medium consists entirely or primarily of photons. The paper begins with a review of analog, discrete, and binary methods of representing information in a computer, followed by a survey of many techniques for implementing binary combinatorial and sequential logic functions with individual optical devices and arrays of devices. Next is a discussion of communication, interconnection, and input-output problems of digital electronic and optical computers at the gate, chip, and processor level. A particular architecture for implementing general sequential optical logic systems including digital optical processors is described. This architecture avoids some of the interconnection problems of electronic integrated circuits and VLSI systems, and offers the potential of non von Neumann parallel digital processors. Finally, the current limitations and future needs of optical logic devices and digital optical computing systems are outlined.

<title>Concepts For Numerical Optical Computers</title>

The approach to the design of an optical computer or processor system has typically been analog in nature in the past. Recently design concepts for a numerical optical processor have evolved in which we see digital techniques implemented with optical devices. This paper describes design concepts for a numerical optical processor which is based on the residue number system.

Solid-State Area Scanning Arrays as Interface Devices Between Optical and Digital Computing Systems–A Simulation Study

This paper describes how, in spite of occasional performance limitations generally due to process defects, large-area solid-state image sensors can be applied to scan pictorial data. First, it is estimated to what extent the direct imaging of pictorial matter onto a defective area-scanning device for acceptable scanning quality is possible. A novel concept is then proposed in which the optically generated Fourier-transform hologram of a picture rather than the picture itself is imaged onto a defective solid-state photosensitive array, scanned, digitized, filtered, and reconstructed by fast Fourier transform (FFT) techniques on a digital processor. The operating principle is discussed and the effects of scanner defects, digitization, and filtering on the scanning quality are investigated by computer simulation.

A Coherent Optical Computer System Using the Membrane Light Modulator

A 32-input coherent optical computer system is described which is driven by a membrane Light modulator (MLM). The MLM has an active area of 4 by 4 mm containing a 32 by 74 array of 2368 38-pm diameter light modulating elements. The optical computer calculates the one-dimensional Fourier transform over 32 points of a phase function in 1 ?s. Both the theoretical and actual operating characteristics of the computer are presented.