Nonlinear optical properties of semiconductor quantum wells with opto-electronic applications.

摘要

In this dissertation are developed models of the optical properties of quantum wells including many-body Coulomb interactions, valence band mixing, excitons, and strain. These models are applied to characterize conventional quantum well optical devices and novel quantum well heterostructure materials and devices.;An excitonic model of carrier-induced exciton saturation including the mixing of heavy and light hole bands is presented. First, the effects of exchange Coulomb interactions on subbands in doped quantum wells are used to account for the larger than expected transition energy of the intersubband transitions observed in experiment. Exchange effects are then combined with valence band mixing, excitons and screening to model optical properties associated with exciton saturation. The model has excellent agreement with experiment in describing absorption saturation in strained and unstrained quantum wells.;The excitonic model is used to determine the dependence of the saturation density on lattice mismatch-induced biaxial strain. For strains at which the light hole and heavy hole bands are widely split, the saturation density is generally linear proportional to the strain but abruptly increases for strains at which the heavy hole and light hole bands are nearly degenerate.;The exciton model with valence band mixing is then applied to terahertz radiation generation from the beating of heavy and light hole excitons, with both bound and continuum excitons treated on an equal footing. Including multiple bound and continuum excitons, discarding the s-states approximation, and properly including the parity of the valence band and exciton states leads to superior agreement with experiment over existing models. The inclusion also leads to the attribution of a discontinuity in the experimental measurements of the terahertz frequency as a function of applied field to a Fano resonance between light hole bound excitons and the heavy hole continuum.;A proposed novel quantum well heterostructure materials system based on calcium fluoride barriers with silicon or gallium arsenide wells is described and characterized. It is demonstrated that such heterostructures may support intersubband transitions at fiber optic wavelengths and can enhance the electro-optic properties of gallium arsenide quantum wells by more than a factor of three by forming dielectric quantum wells.