On realistic modeling of laser-generated ultrasound pulses

A novel formulation of pulsed photoacoustic generation which should facilitate the study of applications of laser-generated acoustic pulses is described and illustrated. This formulation has advantages both in the analytical results obtained and in the ease of numerical calculations. Numerical calculations are presented to illustrate the efficacy of this approach, with emphasis on the effects of finite-source dimensions and on the initial waveform. The origin of the precursor signal is addressed using this formulation. It is concluded that the precursor is due to thermal-to-acoustic mode conversion at the sample surface. In addition, calculations of surface wave progenitors exhibit the advantages of the method in treating near-field propagation.