LOCALIZATION OF 2-DIMENSIONAL EXCITON POLARITONS

The grating-coupler-induced emission and excitation of quantum-well-exciton polaritons (QWEPs) in GaAs-AlxGa1-xAs quantum wells (QWs) and quantum-well wires (QWs) has been studied by photoluminescence (PL) and reflection spectroscopy. The QWEP excitations propagating perpendicular to the grating coupler are observed in PL on the high-energy side of the ground-state heavy-hole exciton transition as an additional strongly polarized signal with the electric field perpendicular to the grating direction. In the QWW the QWEPs show, down to wire widths of Lx=150 nm, a nearly free behavior, i.e., very similar to QWEPs in QW systems. When decreasing the wire width below LxS150 nm the polariton-specific features disappear in the spectra, which we attribute to the localization of the QWEPs. Below Lx=100 nm, the concept of quasi-one-dimensional excitons is an appropriate model to describe the behavior of the observed transitions. © 1990 The American Physical Society.