Ablative excitation of surface acoustic waves in aluminum using UV laser pulses

Surface acoustic wave generation using ablative excitation with ultraviolet laser pulses is studied experimentally in order to quantify the magnitude of response. The acoustic waves are interferometrically measured on the surface of polished aluminum samples at distances of 5 to 40 mm from the excitation spot. Amplitudes of the surface acoustic waves are measured as a function of laser energy (1--60 mJ) and distance from the excitation spot yielding peak-to-peak displacements of 1 to 40 nm. The results are compared to theoretical calculations using the Green's function for a step impulse response. The impulse required to match the measured results is compared to the expected impulse based on plasma pressure scaling in the ablative regime and the experimentally measured response is found to agree within a factor of about 1.7 with the theoretical predicted impulse.