Electro/acousto optic technology has been proposed for a number of advanced programs. A review of these developments and their maturity lead to the apparent conclusion that the primary application of electro/acousto optics may be in ultra-high speed matrix or Fourier multiplication. Their current use and maturity are not sufficient to compete with digital electronics in other areas. A significant amount of basic research is still required to achieve demonstrative results which lead to technology insertion.
A new and general formulation for optical signal processors is advanced. Time and space integrating systems represent the major divisions. Spatially and temporally multiplexed, multi-functional, multi-dimensional and hybrid time and space integrating processors represent the sub-classes considered. Examples of each of these systems and the advantages and disadvantages of each are advanced.
While acousto-optic bulk or surface wave devices represent a radical change in system architecture to overcome the throughput limitations of conventional signal processor technology, GaAs IC's use the conven-tional digital or analog semiconductor processor architectures, achieving greatly improved throughputs by implementing these devices with a radically improved semiconductor. The superior electronic properties of GaAs, as compared with silicon, make possible the achievement of much higher performance levels in GaAs signal processing devices than have been demonstrated with silicon. Only recently, however, have advances in GaAs materials and processing technology made possible the fabrication of such devices as sub1100 ps propagation delay, high density planar GaAs integrated circuits with LS compatible power levels, and high speed (>0.5 GHz), high transfer efficiency GaAs charge coupled devices, 5 which should be capable of multi-gigahertz clocking rate operation. These high performance device technologies should have major impact on the high speed signal processing area, making possible, through their much higher speeds and lower power requirements, system approaches which could not be practically realized with existing silicon technology.
Time integrating acousto-optic processors realize flexible, multi-purpose complex signal processing architectures based on correlation algorithms. One-and two-dimensional techniques are presented including examples of spectral analysis and ambiguity function processing. Non-coherent optical processor implementation using interferometric detection with electronic reference is described and experimental results are given.
The important factors which influence the selection of new acousto-optic infrared materials are discussed, To illustrate how a predicative methodology can be applied to the selection of potentially useful acousto-optic materials, a recent study concerned with the selection, synthesis and crystal preparation of compounds in the Tl-Bi-Te system is described.
Development of acousto-optic devices using the unique properties of tellurium oxide is presently outpacing the capability for manufacturing optical quality material. As long as these devices are in the development stage, no difficulty in meeting production needs is forseen. However, any move to large quantity manufacturing will be limited by the present lack of development of material manufacturing technology.
The power requirements for acousto-optic devices increase with wavelength as λ2, so it becomes extremely important for infrared operation to have very high figure of merit mate-rials available. Potentially important IR applications include scanners for laser radar, choppers for surveillance satellites, and acousto-optic tunable filters for a variety of systems. Higher efficiency materials are also important as thin films for integrated optic devices, such as the spectrum analyzer, and several bulk acoustic wave-optical waveguide concepts. A large number of materials of the sulfosalt class have been identified as having very desirable acousto-optic properties, and will find use in a number of these applications. More development of these materials is required to make them of suitable quality, and new compositions must be examined to achieve high performance.
A brief schematic discussion of work on a microscopic approach to the acousto-optic effect is presented. Two different types of AO materials are discussed in relation to their respective effects on the figure of merit (M2). The distinctions are based on the nature of the atomic bonding (ionic or covalent).
A well-developed technology of depositing ZnO piezoelectric transducers on crystals for bulk-wave acoustic delay devices has been applied to the manufacture of microwave acousto-optic devices. Narrowband acousto-optic units operating at frequencies as low as 250 MHz and as high as 10 GHz have been built. Broadband (1 GHz bandwidth) units have been built with center frequencies ranging from 2.5 GHz to 6.5 GHz. Transducer technology is described, along with characteristics of acousto-optic components built using the deposited transducer technology.
This paper presents a selective review of planar guided-wave acoustooptics with emphasis on those aspects which relate to wideband real-time signal processing. First to be discussed are the working principle and some key analytical results of a basic Bragg modulator which uses a single aperture SAW transducer. Key para-meters relevant to modulation and signal processing are then discussed. Next the design parameters and procedures for wideband Bragg modulators and deflectors which use multiple transducers in Y-cut LiNb03 waveguides are established. Some potential applications of such wideband modulators and deflectors in rf signal pro-cessing are then described. Finally, a brief up-to-date progress report on the implementation of integrated acoustooptical circuits in both LiNb03 and Si substrates is given.
This paper describes the application of electro-optic processor technology to phase direction finding (DF) systems with the objective of providing direction of arrival and frequency sorting of simultaneous pulse and cw signals. The specific processor configurations examined incorporated high bandwidth acousto-optic media which may be configured into a generic amplitude or phase DF system.