Adaptive sensors of rough-surface ultrasonic vibrations based on the polarization self-modulation effect

摘要

New interferometric technique for the linear detection of small out-of-plane vibrations of a rough surface caused by ultrasound is described. The technique is based on the polarization self-modulation effect in photorefractive crystals and does not involve light diffraction. The signal-to-noise ratio of the measured system is approaching to that of the classical homodyne interferometer. The system possesses the large field of view providing the measurements of small phase shift of a speckled wavefront. Moreover, the proposed interferometer is adaptive to slow environment changes with response time about 1 ms keeping ability to measure ultrasonic vibrations of as small amplitude as 0.1 nm. Comparison of the proposed technique with the photorefractive two-wave mixing is given. It is shown that the proposed technique has number of advantages providing higher signal-to-noise ratio and higher sensitivity.