If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally- integrated absorption of light scales with the impurity concentration as N1/6. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor.
Zaitsev, D. A., Il'Ynskaya, N. D., Koudinov, A. V., Poletaev, N. K., Nikitina, E. V., Egorov, A. Y., ... Seisyan, R. P. (2015). Diffusive propagation of exciton-polaritons through thin crystal slabs. Scientific Reports, 5, 11474. https://doi.org/10.1038/srep11474