Plasma pressure scaling of laser ablation generated surface acoustic waves

Summary form only given, as follows. Acoustic probing of materials is a powerful tool in investigating material characteristics and in identifying and locating internal defects in materials. Laser produced plasmas can be employed in order to generate large amplitude acoustic pulses in the material. Large plasma pressures can be generated at the surface even with millijoule level laser pulses leading to large acoustic amplitudes as compared to thermoelastically driven waves, which are often employed. We are studying the application of surface acoustic waves (SAWs) for the non-contact single-surface probing of materials. However, the relation between the amplitude of the SAW and the plasma pressure which excites the wave must be established. UV laser ablatively driven SAWs on aluminum are being studied, generated with either a KrF laser at a wavelength of 248 nm or a 4th harmonic Nd:YAG laser at a wavelength of 266 nm with laser pulse energies in the range of 1 to 60 mJ. The scaling of the SAW amplitude as a function of laser pulse energy and intensity has been measured. In order to compare the experimentally measured SAW waveforms with theoretical expectations a numerical model has been developed.