Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs

Comparative studies of the resonant transmission of light in the vicinity of exciton resonances, measured for 15 few-micron GaAs crystal slabs with different impurity concentrations $N$, reveal an unexpected tendency. While $N$ spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as $N^{1/6}$. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in the semiconductor.