Laser generation and detection of strongly nonlinear elastic surface pulses

Very high amplitude nonlinear surface acoustic wave pulses with 20-100 ns duration and acoustic Mach numbers up to 0.003 were excited in fused silica by nanosecond laser pulses acting on a strongly absorbing overlayer. Absolute measurements were performed with a calibrated dual-probe-laser deflection setup. The formation of shock fronts during propagation and nonlinear broadening of the wave form were observed for the first time. Three nonlinear acoustic constants were evaluated and compared with values resulting from previously measured third-order elastic moduli.