Coherent light is incident upon an acousto-optical cell through which bulk acoustic waves are propagating. These acoustic waves correspond to a signal to be detected and cause periodic variations in the refractive index of the cell which interact with the coherent light. Acoustic frequency components of the propagating waves cause the cell to diffract beams of incident coherent light in a unique direction and to frequency shift each beam of diffracted light. The relative phases of the acoustic frequency components are also imparted to the respective diffracted light beams. Diffracted and undiffracted coherent light beams are recombined so that optical heterodyning takes place. The recombined light beams are focused by a Fourier Transform lens onto a photomixer which detects the frequency difference between the diffracted and undiffracted light beams. By detecting the recombined light beams with a photomixer array or, by deflecting the position of the undiffracted light or by amplitude or phase modulating the undiffracted light, a channelized coherent acousto- optical receiver is achieved which may function as part of a rapidly tunable bandpass filter.
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