Signal processing with surface waves via the double acousto-optic interaction

Abstract

Optical diffraction by two successive surface acoustic waves was used to achieve various signal‐processing operations. Expressions were derived for the frequency spectrum and bilinearity factor associated with this double interaction and these formulas were verified experimentally using Fabry‐Perot interferometry. An aperture function formalism was used to demonstrate that the doubly diffracted field corresponds in form to that required for real‐time convolution. The addition of a simple lens system extended the capability of this technique to a full range of processing functions. The following operations were demonstrated for pulses of the order of 1 μs: squaring convolution, squaring correlation, variable time expansion, variable time compression, time inversion, and image scanning. This processor is characterized by large bandwidth since the diffraction takes place in the Raman‐Nath limit up to GHz frequencies.