Bragg quantum wells in weak confinement regime

Abstract

The optical properties of Bragg quantum wells are studied for exciton confinement under center-of-mass quantization. A variational model of Wannier exciton envelope function, that embodies the correct boundary conditions for center-of-mass, is adopted for calculation. The present non-adiabatic exciton model is compared with adiabatic results and with heuristic “hard sphere” model. The radiative self-energy of a single-quantum well (SQW) and multi-quantum wells (MQWs) are computed in the semiclassical framework, and in effective mass approximation, by self-consistent solution of Schroedinger and Maxwell equations. This microscopic solution is free from “fitting” parameter values, except for the non-radiative broadening, and also the exciton dead-layer and the additional boundary condition are not taken ad hoc, but come coherently from the variational principle and self-consistent Schroedinger-Maxwell solution. Dispersion curves of exciton-polariton propagating in a MQW, under Bragg condition, are studied by selected numerical examples. The case of optical gap in correspondence of higher excited states is studied, and, moreover, the interesting effect of gap enhancement or inhibition, in correspondence of non-resonant Bragg energy, will be addressed.