Analysis of polarized light generation in anisotropic strained quantum dots

Abstract

A theoretical analysis of the optical characteristics and polarization properties of quantum dot laser which uses interband transitions in shape asymmetric InGaAs/GaAs QDs is presented. We use multi-band effective mass k.p model with the strain effect taken into account to compute the electronic structure of asymmetric QDs. In-plane shape asymmetry in QDs is accounted through the anisotropic parabolic potential. The optical gain spectrum is calculated using the density matrix approach. We have solved coupled set of rate equations numerically using fourth-order Runge Kutta method to analyze the dynamic characteristics of InGaAs/GaAs quantum dot laser. The effect of shape anisotropy, material composition, carrier densities and strain on light emission polarization ratio has been studied. The dependence of gain on polarization direction has been explained in terms of the valence band mixing. The polarization is found to increase almost linearly with anisotropy parameter and decreases with the material composition. Furthermore, it is demonstrated that anisotropy and strain can be used to control the polarization. We found that the output has preferential polarization properties depending on the QD structure and composition.