Spatial and temporal frequency domain laser-ultrasound applied in the direct measurement of dispersion relations of surface acoustic waves

Abstract

We present a laser-ultrasound measurement technique which combines adjustable spatial and temporal modulation of the excitation laser beam. Our method spreads the intensity of an amplitude modulated continuous wave laser over a micro-scale pattern on the sample surface to excite surface acoustic waves. The excitation pattern consists of parallel, equidistant lines and the waves generated from the individual lines interfere on the sample surface. Measurement is done in the spatial-temporal frequency domain allowing the direct determination of dispersion relations. The technique performs with high signal-to-noise-ratios and low peak power densities on the sample. © 2013 American Institute of Physics.