Evidence of slow acoustic surface waves on a 1D phononic surface by a pulsed laser spectroscopic technique resolved in time and space

¹ European Laboratory for Non-Linear Spectroscopy (LENS), Università a di Firenze - Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy EU
² Dipartimento di Fisica ed Astronomia, Università di Firenze - Via Sansone 1, I-50019 Sesto Fiorentino, Firenze, Italy, EU
³ Istituto Nazionale di Ottica (INO)-CNR - Largo E. Fermi 6, I-50125, Firenze, Italy, EU

^a taschin@lens.unifi.it

Received: 4 October 2011
Accepted: 18 January 2012

Abstract

We report the investigation of surface acoustic waves (SAWs) propagating on a 1D phononic surface (PS) by the heterodyne-detected transient reflecting grating technique. A suitable experimental configuration enables the excitation of traveling SAWs with variable wave numbers and the measurement of their propagation with temporal and spatial resolution. Using the full characterization of the band diagram of this PS, as reported previously (Malfanti I., Taschin A., Bartolini P., Bonello B. and Torre R., J. Mech. Phys. Solids, 59 (2011) 2370), we studied the dispersion properties of the SAWs as the wave number approaches the Brillouin zone edge. SAW-packet group velocities show a clear slowing-down process approaching the BZ edge, with a measurable minimum velocity of about 140 m/s