LASER GENERATION OF ULTRASOUND USING A MODULATED CONTINUOUS-WAVE LASER-DIODE

A modulated continuous wave diode laser was used to generate ultrasoni c Lamb waves in a thin steel plate. No surface damage was evident on t he sample, a feature due to the low power density of the acoustic sour ce in contrast to the high power pulsed laser systems usually employed for laser-ultrasound generation. The Lamb waves were monitored using a surface bonded optical fiber interferometer whose output was correla ted with the pseudorandom binary sequence used to modulate the laser d iode. In this fashion, it was possible to record a time domain history of the ultrasonic propagation in the sample. (C) 1998 American Instit ute of Physics.