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

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.