Characteristics of Acoustooptic Devices for Signal Processing

Abstract

This paper presents an overview of acoustooptic devices for signal processing. These devices consist of one or more ultrasonic delay lines which have optical readout capability for simultaneous noninvasive access to the entire acoustic field. The A0 devices can be considered as integrated arrays of delay elements and mixers which modulate ultrasonic field information onto ihe optical field The optical signal fields can be manipulated and combined with great speed using optical techniques such as imaging, Fourier transformation, interferometry, and spatial filtering. These can be combined lo produce effective signal processing subsystems such as signal spectrum analyzers and correlators. Important performance characteristics include bandwidth, delay, mixer efficiency. amplitude and phase response, intermodulation distortion, and dynamic range. These characteristics are limited by the propagation characteristics of acouslic and optical fields as well as the acoustooptic interaction. Performance characteristics have been whanced using desians including effects such as anisotropic propagation and birefringent interaction and u;lrasonic beam steering. Optical filtering techniques have further improved on intrinsic device properties. The acoustooptic devices can be classifiecr in several ways; for example, bulk acoustic wave vs. surface acoustic wave, bulk vs. guided optical waves, skew vs. axia! optical illumination. Some comparative advantages and applications of different device types will be discussed.