Determination of the nonlinear ultrasonic parameter using a Michelson interferometer

Abstract

We describe an accurate optical technique for determining the nonlinear ultrasonic parameter . Our technique uses a path-stabilized Michelson laser interferometer, in contrast to more conventional methods which use piezoelectric or capacitive detectors. Features include high spatial resolution (typically ), flat bandpass response over a wide range (> 30 MHz) and simple self-calibration. We demonstrate the technique using a fused silica disc 19.15 mm thick and a fundamental frequency of 10 MHz. For comparison, was also obtained for the same specimen using capacitive and piezoelectric detectors. Errors and correction factors for all three methods are discussed; in particular, we note the importance of including ultrasonic diffraction effects. When such corrections are applied, we obtain the following results: , and . These values are in reasonable agreement with each other as well as with published values of .