Optical lock-in vibration detection using photorefractive frequency domain processing

optical method for vibration detection and spectral analysis based on photorefractive frequency domain processing is presented. The method utilizes the photorefractive effect in selected materials (bismuth silicon oxide) for synchronous detection of the optical phase shift of an object beam scattered from a vibrating specimen surface. Four-wave mixing and lock-in detection allow measurement of both the vibration amplitude and phase. Narrow-bandwidth detection can be achieved at frequencies from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. (C) 1996 American Institute of Physics.