OBSERVATION OF WAVELENGTH-DEPENDENT GENERATION EFFICIENCY OF LASER-INDUCED ULTRASONIC SURFACE ACOUSTIC-WAVES ON CERAMIC MATERIALS

In this work, the efficiency of laser generation of surface acoustic w aves (SAWs) in ceramic materials is reported to be wavelength dependen t. A pulsed Nd:YAG laser operating at wavelengths of 1064 or 532 nm wa s used to generate SAWs on ceramic (silicon nitride and silicon carbid e) and metal substrates. It was observed that 1064 nm radiation is mor e efficient than 532 nm radiation for SAW generation on ceramics, wher eas the opposite is the case for metals. While the wavelength dependen ce of SAW generation efficiency in metals is due to stronger optical a bsorption at the shorter wavelength, the dependence for the ceramics i s attributed to a longer absorption length at the longer wavelength. ( C) 1997 American Institute of Physics. [S0003-6951(97)04752-9].