EXPERIMENTAL-STUDY OF DIRECTIVITY PATTERNS OF LASER ULTRASOUND IN AN UNPOLARIZED PZT CERAMIC IN THE THERMOELASTIC REGIME

The experimental longitudinal directivity patterns of laser-generated ultrasound for both line and disc laser sources, in an unpolarized PZT -4 ceramic in the thermoelastic regime, are presented. The exciting so urce is a Q-switched Nd:YAG laser operating at the wavelength of 1.06 mum and having a pulse width of 8 ns and maximum pulse energy of 200 m J. The acoustic pulses are detected by a 5 MHz piezoelectric ultrasoni c transducer. The results show that there are noticeable differences b etween the directivity patterns in the non-metal PZT and those in the metal aluminium. Discussions of the observations are offered.