Evidence for Spatial Propagation of Photon-like Polaritons Generated by Exciton–Exciton Scattering in a GaAs/AlAs Multiple-Quantum-Well Structure

Abstract

We have investigated the polariton characteristics of the photoluminescence (PL) due to exciton-exciton scattering at 10 K in a GaAs/AlAs multiple-quantum-well structure with the use of spatially-resolved PL spectroscopy. We found that the PL band from the exciton-exciton scattering, the so-called P emission, is detected only at spots along a sample edge which is spatially separated from an excitation spot. In contrast, the PL bands attributed to the exciton and biexciton were observed only at the excitation spot. Because the exciton-exciton scattering occurs at the excitation spot, the appearance of the spatially-separated P-emission spot demonstrates that the photon-like lower polariton, which is the final state of the exciton-exciton scattering process, propagates along the interface, leading to conversion to a photon. The spectral shape of the P-PL band detected at the spatially-separated spot exhibits a fringe pattern, which is quantitatively explained by the Fabry-Pérot interference originating from the spatial separation of the P-emission and excitation spots.

Spatially-Resolved Photoluminescence Study of Temperature Dependence of Exciton Inelastic Scattering Processes in a ZnO Thin Film

“…This fact suggests that the photon-like LP, which is the final state of the exciton inelastic scattering process as described above, propagates along the in-plane direction from the excitation spot, and then it is converted to a photon corresponding to the P emission at the film edge at which the translational symmetry is broken. 21) As a result, the P-PL band is selectively observed at the spatially-separated spot. The selective observation of the PL band from the P emission or H emission at the spatially-separated spot was confirmed in the whole temperature region up to 290 K. Note that a tail of the exciton absorption band extends to a low energy side with an increase in temperature owing to the Urbach rule; however, the polariton nature of the P emission and H emission prevents the reabsorption effect on the P-PL and H-PL bands.…”