A laser probing system for characterization of SAW propagation on LiNbO/sub 3/, LiTaO/sub 3/, and quartz

A nondestructive high-resolution technique for the optical detection of the phase and amplitude of high-frequency surface acoustic wave (SAW) devices is presented. The setup incorporates a mode-locked ps-laser, harmonic mixing, and coherent detection. Dynamic range and minimum detectable surface displacement were 50 dB and 1 pm//spl radic/(Hz), respectively. The probing technique allows not only the measurement of the SAW field but also the precise direct determination of the phase velocity which is a fundamental design parameter in SAW technology. We present experimental results of the phase velocity of both SAW and Leaky SAW modes on quartz, LiNbO/sub 3/ and LiTaO/sub 3/ with an accuracy of up to 1.5.10/sup -5/. Our results agree very good with theory and other experiments.