ENHANCED COHERENT PHONON GENERATION BY PERIODIC EXCITATION WITH Q-SWITCHED AND MODE-LOCKED LASER-PULSES

Enhanced coherent phonons (ultrasonic waves) produced by periodic excitation of transient grating with light pulses from a Q-switched and mode-locked laser were observed when the resonance condition v=nf was satisfied, where v is the phonon frequency, f the repetition frequency of the pulses and n an integer. The enhancement was observed for phonons with frequencies from 81.8 MHz to 654 MHz, and the maximum enhancement was about 100 in intensity. The dynamics involved was analyzed by developing the theory conforming to our experimental condition. Sound velocities and phonon intensities were measured in ethanol etc. containing a small amount of dye. © 1990.