Resonant Brillouin Scattering of Excitonic Polaritons in Gallium Arsenide

Abstract

We report the first experimental observation of resonant Brillouin scattering of excitonic polaritons in a semiconductor. The usual symmetric Brillouin doublet becomes an asymmetric multiplet when the incident light energy is scanned through the $n=1$ exciton resonance and allows a direct measurement of the polariton dispersion curve. In GaAs we determine a longitudinal-transverse splitting of 0.08 \ifmmode\pm\else\textpm\fi{} 0.02 meV and a translational mass ${M}_{\mathrm{ex}}=(0.6\ifmmode\pm\else\textpm\fi{}0.1){m}_{0}$ for the [100] heavy exciton. The excitions couple preferentially to LA phonons.