Using degenerate four-wave-mixing technique the acoustic wave produced in transparent microstructured optical materials can be determined. The light source used in this paper was a mode-locked, Q-switched Nd:YAG laser operated at 532 nm with pulse width of approximately 20 ps. The laser beam was split into three pulses. By spatially overlapping inside the sample with an angle in a backward propagating scheme. A laser induced periodic interference pattern which serves as grating was formed in the sample. The third, `probe', beam incident on the region in the direction satisfied by the Bragg condition. The diffracted signal brings the information of the produced acoustic wave. The incident laser pulses coupled to the acoustic field of the material through effects of thermally induced acoustic strain and electrostrictive coupling. This results in a generation of two counterpropagating ultrasonic acoustic waves in the grating wave vector direction, which is so- called the Laser Induced Phonon Spectroscopy.

Date Published: 22 May 2000
PDF: 7 pages
Proc. SPIE 4072, Fourth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (22 May 2000); doi: 10.1117/12.386728

Published in SPIE Proceedings Vol. 4072:
Fourth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)