Anisotropy effect on the linear and nonlinear optical properties of a lased dressed donor impurity in a GaAs/GaAlAs nanowire superlattice

Abstract

We have developed a finite difference method as well as have used compact density-matrix approach to analyze the effect of laser radiation and geometrical anisotropy on the optical properties of a GaAs/Ga1−xAlxAs nanowire superlattice (NWSL). In this regards the transition between ground and first excited states is considered to obtain the linear, third order nonlinear and total optical absorption coefficients (ACs) and refractive index (RI) changes. Our calculation shows that (I) presence of laser radiation causes an increment in ACs and RI changes and shifts optical spectrum toward lower energies. (II) For small values of volume of QDs the magnitude of optical ACs and RI changes is increased (decreased) by an oblate (a prolate) deviation from spherical QDs whereas for large QDs’ volumes an opposite behavior is observed. (III) The nonlinear terms of ACs and RI changes are very sensitive to laser radiation. Additionally, the saturation in optical spectrum can be adjusted by magnitude of laser radiation and shape of QDs involved in the NWSL.