First principles study on optical properties of GaAs saturable absorbers with native defects

Abstract

First principles calculations based on the plane wave pseudo-potential method have been carried out to study effects of intrinsic point effects in GaAs saturable absorbers on the related electronic structures and optical properties. The defect energy levels corresponding to each kind of the intrinsic point defect and their electron occupancy are analyzed from the aspects of band structure and partial density of states (PDOS). Furthermore, the impacts on the optical properties of GaAs saturable absorbers made by the native point defects are also obtained. It can be found that the absorption edges of the GaAs with VGa defect, VAs defect or GaAs defect exhibit substantial redshifts, which is mainly attributed to the defect energy levels in the band gap, and the absorption coefficient of the GaAs crystal with VGa defect, VAs defect or GaAs defect is bigger than those with other defects in near-infrared range. The dielectric function and the refractive index of GaAs crystal with VGa defect, VAs defect or GaAs defect show redshifts in near-infrared region too. The analysis of the optical properties of GaAs crystal with intrinsic point defects will be helpful in guiding the application of the GaAs crystal as saturable absorber in solid-state laser.