Laser generation of ultrasound for process control using optical fiber arrays

Abstract

This paper reviews recent work on the use of optical fiber arrays to enhance laser generation of ultrasound. Experimental and numerical directivity patterns are presented, obtained using optical fiber arrays to generate longitudinal, shear, and surface waves. Comparisons of the directivity patterns for a single light source and for the fiber array will be presented and discussed for each of the above waves. Also shown will be some experimental results on array gains. This discussion will be limited to sound generation in the thermoelastic (linear) range. The optical fiber array can be used to control both the directivity and the type of elastic wave generated by the laser light. The noncontact fiber array generation can be combined with a noncontact EMAT or laser Doppler receiver to achieve a system for ultrasonic on‐line inspection and control of manufacturing processes. The above technique for sound generation and reception is particularly useful in hostile and hard to reach environments. [Work supported by the National Science Foundation.]