Picosecond ultrasonics

The generation and detection of ultrasonic waves with picosecond time resolution are described. With picosecond ultrasonics, the frequency range of acoustic waves is extended into the 100-GHz range. It allows the investigation of thin-film materials, microstructures, and materials with large acoustic attenuation. Velocity and attenuation measurements on a variety of thin films are reviewed. The results on complex microstructures, including multilayers, are presented.< >