Watching ripples on crystals

Abstract

A method for real-time imaging of coherent surface phonons was demonstrated. Surface phonon wave packets were thermoelastically excited in thin metal films on transparent substrates with optical pulses. A 140 nm polycrystalline chromium film was prepared by electron beam deposition on a 1 mm crown-glass substrate. Results indicated that the imaging technique allowed direct access to the dispersion characteristics of the wave propagation.