A coherent optical correlator can operate as a generator of complex waveforms when it is driven by a short-duration carrier pulse. However, the poor signal-to-noise ratio which results usually precludes operation in this mode. The ultrasonic shutter described herein can improve the signal-to-noise ratio by a factor approaching the time-bandwidth product of the system. No moving mechanical parts are involved.
W. T. Maloney, "An Ultrasonic Shutter for Noise Reduction in Real-Time Optical Correlators," Appl. Opt. 8, 443-446 (1969)