Efficient generation of acoustic pressure waves by short laser
The displacement of laser-generated ultrasonic bulk waves in polycrystalline metal samplers consists of signals travelling with pressure wave velocity as well as with shear wave velocity. The waveform obtained depends on the incident laser power density and the laser energy. It is found that there is a specific power density and the laser energy. It is found that there is a specific power density I sub O at which only a maximum pressure pulse is generated whose magnitude is proportional to the laser energy. Furthermore, the angular distribution of the pressure pulse shows that most of the acoustic energy is radiated in the forward direction. The Fourier spectrum of the pressure pulse is also evaluated.