Generation of ultrahigh-frequency tunable acoustic waves

We demonstrate versatile generation of ultrahigh-frequency, tunable acoustic waves. A novel retroreflection-based pulse shaper is used to generate optical pulse sequences whose frequency is tunable in the 2–2000 GHz range through movement of a single delay line. Multiple-cycle acoustic waves are detected interferometrically at the back of a 15 nm aluminum transducing film and the back of a film-sample-film assembly configured for narrowband acoustic spectroscopy.