A small part of a focused laser beam in a Mach–Zehnder arrangement is used for the detection of high-frequency pressure waves. The interferometer is stabilized on an interference slope by means of a simple electro-optical feedback system. The method introduces only little perturbation to the pressure field and yields the true pressure history p (t) with a submicrosecond time resolution. Several examples of registrations show the capability of this ideal microphone.
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G. Smeets (1977) studied this question.