Exciton-resonant detection of high-frequency surface acoustic waves from subwavelength metal gratings

TL;DR

This paper demonstrates a highly sensitive all-optical method for detecting high-frequency surface acoustic waves in GaAs/AlGaAs structures using exciton resonance, achieving improved sensitivity through polarization-resolved pump-probe techniques.

Contribution

It introduces a novel exciton-resonant detection technique for high-frequency SAWs with enhanced sensitivity and provides a theoretical model for different detection schemes.

Findings

Detection sensitivity increased by an order of magnitude using exciton resonance.

High-frequency SAWs up to 30 GHz successfully generated and detected.

Theoretical model matches experimental detection schemes.

Abstract

We report on all-optical generation and detection of high-frequency (up to about 30 GHz) surface acoustic waves (SAWs) in GaAs/AlGaAs heterostructures with short-period Au gratings on top. A highly sensitive method for SAW detection is demonstrated using a polarization-resolved pump-probe technique that exploits the narrow exciton resonance in high-quality GaAs. The elastic strain of the SAW modulates the exciton energy in the time domain. As a result, even a small deformation produces 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 off-resonant conditions. A theoretical model is developed that considers two detection schemes: one accounting for probe light diffraction and one corresponding to a non-diffractive situation.