Analytical technique for determining the polarization dependence of optical matrix elements in quantum wires with band-coupling effects

Abstract

We present an analytical technique for determining polarization-dependent optical transition matrix elements in quantum wires which rigorously incorporates the effects of band coupling. Using this technique, we examine the polarization anisotropy of the two lowest energy optical transitions in a GaAs quantum wire. Contrary to assumptions employed in previous studies, we show that the valence states involved in these transitions are a strong admixture of light and heavy hole character. The lowest energy transition is found to be four times stronger for electric fields oriented parallel to the wire than for the perpendicular orientation. In contrast, the next highest transition does not interact with optical waves polarized along the wire axis. We discuss sources of error which arise in simpler one-band models of this phenomenon in addition to the neglect of band coupling and show that the coupled band model presented here is essential for predicting these effects.