Broadband optical detection of ultrasound by two-wave mixing in a photorefractive crystal

Abstract

A method which allows broadband (from typically 1 KHz) optical detection of ultrasound with large light gathering from a scattering surface is presented. The wave scattered by the surface is mixed inside a BaTiO3 photorefractive crystal with a pump wave directly derived from the laser to provide a sideband-free reference wave. A polarization configuration which provides sensitive and linear ultrasonic displacement detection is described. This method is demonstrated by detecting laser generated ultrasound.