THE CO₂LASER - A NEW ULTRASOUND SOURCE

The generation of ultrasound in metals and plastics by a pulsed TEA CO2 laser is reported. In the case of metals a technique of laser induced air breakdown above the metal surface produces a rapidly expanding plasma which applies a normal force, with approximately Heaviside time dependence, to the surface resulting in the generation of an ultrasonic pulse. In plastics the ultrasound is generated by the absorption of C02 radiation producing a buried thermoelastic source close to the sample surface. In both cases the interaction leaves no surface damage