Pulsed-laser generation of ultrashort acoustic pulses: Application for thin-film ultrasonic measurements

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Abstract
We demonstrate nondestructive optoacoustic generation and detection of acoustic pulses of 1‐ns duration in condensed matter. Such optoacoustic pulses are at least one order of magnitude shorter than those previously reported. These narrow acoustic pulses find new application for thin‐film pulse measurements, which are not possible with conventional transducer techniques. Round trip echo times are measured to 1% accuracy for stainless steel films of 12‐μm thickness. This provides a new high accuracy thickness measurement in a pulsed mode. Ultrasonic attenuation for the narrow acoustic pulses is very large and is also measured.