High-frequency surface acoustic waves: Generation with sub-optical wavelength metal gratings and detection at the exciton resonance

Abstract: We demonstrate all-optical generation and detection of high-frequency (up to ~30 GHz) surface acoustic waves (SAWs) in GaAs/AlGaAs heterostructures with short-period Au gratings on top. We present a sensitive method of SAWs detection by means of a polarization-sensitive pump-probe technique that exploits the narrow exciton resonance in high-quality GaAs. The elastic strain of the SAW causes modulation of the exciton energy in the time domain. As a result, even a small deformation leads to a noticeable change in the dielectric function at the detection wavelength leading to an order of magnitude increase in the detection sensitivity as compared to detection apart from the resonance. A theoretical model is developed that considers two detection schemes: one accounting for probe light diffraction and one without.