Laser generation and detection of interface waves for the acoustic spectroscopy of liquids

The pulsed heating of the interface between a solid and a liquid leads to the excitation of acoustic interface waves. These interface waves are detected at a variable distance from the generation region by means of a beam deflection setup. By evaluating the amplitude and phase spectra (using a Fast Fourier transform) of two wave pulses at two different source-receiver distances, the velocity of propagation and the attenuation of the interface waves are measured as a function of frequency (bandwidth of 50 MHz). By fitting these experimentally determined results to theory it is possible to determine the acoustic properties of the liquid as a function of frequency.