Photoacoustic point source

We investigate the photoacoustic effect generated by heat deposition at a p oint in space in an inviscid fluid. Delta-function and long Gaussian optica l pulses are used as sources in the wave equation for the displacement pote ntial to determine the fluid motion. The linear sound-generation mechanism gives bipolar photoacoustic waves, whereas the nonlinear mechanism produces asymmetric tripolar waves. The salient features of the photoacoustic point source are that rapid heat deposition and nonlinear thermal expansion domi nate the production of ultrasound.