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A novel phase-sensitive optical probe for observation of nonlinear surface acoustic wave (SAW) has been constructed. The probe operates in the acoustic pulse mode that allows input powers as high as 20 W. Light from a solid-state laser diode is modulated at frequencies up to 1 GHz that enables a broad-band detection of SAW and its harmonics. Measurement of harmonic generation has been carried out on LiNbO3single-crystal plates, and information on both amplitudes and phases of the harmonics has been obtained. The developed experimental technique provides a foundation for optical detection of the waveform of nonlinear SAW, and is aimed at the observation of SAW solitons.

A computer-controlled laser probe surface-acoustic-wave (SAW) observation system was constructed, which facilitates reconstruction of 3-dimensional images of travelling Rayleigh SAWs. Vivid images of a propagating single SAW and two colliding SAWs on a glass plate were observed by this system. The system is thus used as a powerful tool for elucidating the dynamic behaviors of SAW, especially for identification of surface acoustic solitons.