To nondestructively detect surface defects that reduce the strength of ceramics and structural materials of micromachines, we previously developed the phase velocity scanning method. By using scanning interference fringes generated by two laser beams whose frequencies are shifted, the method can generate a 110 MHz surface acoustic wave (SAW). However, the frequency of the SAW depends on the frequency of the Bragg cell used, thus making the upper-limit frequency about 110 MHz. In this study, we propose multiple use of Bragg cells in series, and successfully generated a 200 MHz SAW.
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