Dispersion and damping of multiple quantum-well polaritons from resonant Brillouin scattering by folded acoustic modes

Abstract

We demonstrate that resonant Brillouin light scattering using ultranarrow lasers and high-resolution spectrometers provides unique access to the polariton lifetimes, a key parameter in their formation and dynamics. In very high-quality GaAs/AlAs multiquantum wells, we observed significant variations across the resonance of the folded acoustic phonon linewidths, in addition to varying line shifts as reported in bulk materials. Inclusion of the dispersion and lifetime of both incoming and outgoing polaritons allows an excellent quantitative description of the results. This high-resolution Brillouin study opens different perspectives for the study of ground and excited polariton states and their dynamics in confined systems.