Multiple Cavity Laser Array Source for Laser Generation of Ultrasound
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Abstract
A significant expansion of the utility and availability of laser ultrasound as a nondestructive evaluation technique will come as advancements are made to find practical and inexpensive means to improve the detection sensitivity so that it begins to approach more closely the performance of conventional piezoelectric contact ultrasonic methods. Among the several opportunities where technological advances could enhance laser ultrasonic sensitivity, one is the advantageous use of modulated laser array sources to control the nature of the generated ultrasonic signal so that it can be made more readily detectable by optical interferometer receivers. The detection limit of all optimally designed and implemented optical receivers is that imposed by the presence of broadband shot noise so that in every case, the signal-to-noise ratio, SNR, depends upon such parameters as the amplitude of the detected elastic wave, δ, and the bandwidth, B, of the receiving system in the following manner: