Self-induced electrooptic modulator - a new approach for homodyne detection of ultrasonic surface displacement

摘要

New interferometric technique based on the polarization self-modulation (PSM) effect in photoconductive electrooptic crystals for the linear detection of small out-of-plane vibrations of a rough surface caused by ultrasound is described. The technique is more advantageous than the widely used photorefractive two-wave mixing technique. Basing on the vectorial theory of light diffraction in photorefractive crystals of cubic symmetry, the procedure of the PSM-interferometer optimization is proposed. The highest sensitivity of a PSM interferometer with fast semiconductor crystals is achieved in the transversal configuration when both the external electric field and grating vector are parallel to the < 110 > axis. The sensitivity of the adaptive PSM-interferometer is only two times smaller than the sensitivity of the classical homodyne interferometer.