Arthur D. Fisher

Optical guided‐wave interactions with magnetostatic waves at microwave frequencies

Interaction of guided optical waves with microwave magnetostatic waves in yittrium iron garnet thin films has been demonstrated. TM↔TE mode conversion induced by codirectional (and contradirectional) magnetostatic waves was experimentally observed with conversion efficiencies of up to 4%. Theoretical expressions for this interaction are given and compared with observations. The thin‐film geometry demonstrated could make a practical number of optical signal processing devices in the 1–20‐GHz range.

Optical implementations of associative networks with versatile adaptive learning capabilities.

Optical associative, parallel-processing architectures are being developed using a multimodule approach, where a number of smaller, adaptive, associative modules are nonlinearly interconnected and cascaded under the guidance of a variety of organizational principles to structure larger architectures for solving specific problems. A number of novel optical implementations with versatile adaptive learning capabilities are presented for the individual associative modules, including holographic configurations and five specific electrooptic configurations. The practical issues involved in real optical architectures are analyzed, and actual laboratory optical implementations of associative modules based on Hebbian and Widrow-Hoff learning rules are discussed, including successful experimental demonstrations of their operation.

The Current Status Of Two-Dimensional Spatial Light Modulator Technology

An introduction and comparative overview to the state of the art of two-dimensional spatial light modulator technology is provided, touching on the basic operation and performance of most of the more promising electronically- and optically- addressed device technologies. The fundamental functional capabilities and potential applications of these light control devices are also discussed, and some projections are offered on the future directions of spatial light modulator technology.

Photoemitter Membrane Light Modulator

A potentially high-performance, optically addressed spatial light modulator, called the photoemitter membrane light modulator (PEMLM), is being developed. The structure, operational theory, performance objectives and limitations, and experimentally observed performance of this device are discussed. A grid structure incorporated into the PEMLM is shown to significantly enhance the active removal of electrons from the membrane by secondary emission. The PEMLM offers the potential for framing rates in excess of 1 kHz, 50 1p/mm resolution, storage times of days, sensitivities of less than 1 nJ/cmz, and an intrinsic ability to perform such image processing operations as thresholding, contrast modification, image addition and subtraction, binary logic, and optical synchronous detection.

Implementations Of Adaptive Associative Optical Computing Elements

Parallel-processing architectures consisting of multiple optical adaptive associative modules, cascaded and interconnected in particular configurations, are being developed for applications requiring the manipulation of massive amounts of symbolic information. Specific optical implementations of the individual adaptive heteroassociative modules (elements) are presented and their operational theory and behavior are discussed. These modules adaptively learn and store a series of associations in the form of electronic charge distributions in an optical control device called a microchannel spatial light modulator.

Spatial light modulators for optical information processing: introduction by the feature editors.

Some twenty-five papers (including two Letters to the Editor) in this 15 November 1989 issue of Applied Optics consider the technology and use of spatial light modulators. This brief introduction reviews the field.

Device Developments for Optical Information Processing

Publisher Summary This chapter emphasizes those developments in the three classes of devices (light sources, modulators, and detectors) that address the optical processing needs and points out the specific promising directions for development. The performance of light sources, modulators, and detectors drives progress in the utilization of optical techniques in signal processing and computing. Of the three device categories, optical sources are the most developed. Most developments of relevance are pointed toward the improvements in semiconductor laser diodes to achieve better optical beam outputs because the advantages of such lasers in size, weight, and power efficiency are well known. In optical processing applications, it is desired to manipulate the 2-D fields that are spatially as large as possible, that is, the photodetector throughputs must be commensurately large, even if the data array to be detected has been reduced in dimension to 1-D or even a single channel. Optical processing architectures determine the format of the output data array, but the performance of photodetectors determines the efficacy of the alternative candidate architectures.

Magnetostatic Wave Devices for Integrated-Optical Signal Processing

Rrw diffraction of li@t by mgnetostatlc waves (ntNs) is merging as a promising new technolow for optical signal processing, offering larm time-bandwidth optical pmcessirg at microwave frequencies of 1 to 20 GVz and higher. Mffraction of Widedaptical waves by transversely-propagating nametostatic waves and collinear TEc+TY mde conversion induced by WWs have been demonstrated. Viffraction efficiencies of %/watt, 4% total diffraction, and a mdulation dynamic range of -30 db have ken observed. The underlying theory of the transverse WW-optical interaction is presented, including the development of expressions for optical diffraction efficiency as a function of WW mer and frequency, device gemtry, mterials properties, and other relevant parameters. Potential inteqratedaptica l signal processing applications are mntioned, including spectrum analyzers, convolvers/correlators, deflectors, nonrecimocal optical isolators, and tunable narrowband filters.

Special Information Processing Capabilities Of The Photoemitter Membrane Light Modulator (PEMLM)

The PEMLM has been used to demonstrate several real-time image-processing operations: contrast reversal, edge enhancement, image addition/subtraction, and synchronous detection of time-modulated light in a scene. Experimental results will be presented, and the relationship between the device physical parameters and performance characteristics will be discussed. Future developments to improve the PEMLM performance will also be described. Demonstration of quantum-limited sensitivity, millions of resolution elements, and frame rates greater than a kilohertz is expected in the near future.

A High Performance Photo-Emitter Membrane Spatial Light Modulator

A potentially high-performance, optically-addressed, spatial light modulator, called the photo-emitter membrane light modulator (PEMLM) is being developed. The operational theory of the PEMLM is presented, accompanied by a discussion of its ultimate performance objectives and limitations. The PEMLM offers the potential for framing rates in excess of 1kHz, 50 1p/mm resolution, storage times of days, extreme sensitivities of less than 1 nJ/cm2, and an intrinsic ability to perform such image processing operations as thresholding and hardclippiny, contrast reversal and enhancement, image addition and subtraction, and optical binary logic. A developmental laboratory prototype has been constructed.