Velocity measurements of laser-generated ultrasound by using laser arrays and a phase modulated Michelson interferometer

摘要

A phase modulated Michelson interferometer for laser ultrasonics is described. The operation point in the interferometer is the minimum intensity of interference patterns. This scheme allows the use of a high power laser to improve the sensitivity without the saturation of a optical detector. Ultrasonic waveforms with amplitude of a few 10 pm have been obtained by using a 2 W laser. For generation, an array of 4 pulsed Nd:YAG lasers is used to excite toneburst ultrasonic echoes. The echo round trip time can be measured precisely by cycle for cycle overlapping. Several experimental results of ultrasonic waveforms are presented.