Laser Generation of Ultrasound.

An experimental and analytical study has been conducted into the use of carbon dioxide TEA lasers to generate ultrasonic waves. When the laser is fired at a plastic target, waves with a peak-to-peak pressure of 10 bars are generated. Teflon and Mylar were the most effective. There was no damage to the plastic, even after several hundred shots. This was not the case for glass or aluminum with a much smaller absorption depth and lower conversion efficiency. The sound wave could be directed by using an off axis zone plate. This generated a 10 MHz tone burst, 45 degree off axis with a duration of 4 microseconds. A theoretical analysis of the phenomena is given which accounts for the waveforms and peak pressures measured.