Quantum interference and gain processes in optically-driven n-doped quantum wells with Ξ configurations

Abstract

We study the electron distributions, intersubband dephasing rates and linear gain and absorption spectra in n-doped asymmetric quantum wells driven by one or two IR fields. The fields couple the partially occupied ground conduction subband of the quantum well to the second subband, and couple the latter to the third subband forming a Ξ configuration. By consistent treatment of the electron–electron scattering process and inclusion of dynamic screening we show how these processes generate non-Fermi electron distributions in the coupled subbands and contribute dynamically to the dephasing rates associated with transitions between the ground subband and higher ones. We also show how these processes affect the gain and absorption spectra in the first to second and the second to third subband transitions when the system is monitored by a weak probe field. These transitions and that between the first and third subbands include dispersive features and strong gain-absorption suppression. We explain these results in terms of extension of the hyper-Raman process, one- and two-photon dressed effects, stimulated Rayleigh scattering and quantum interference effects.