Effect of anisotropy of band structure on optical gain in spherical quantum dots based on PbS and PbSe

Results of an experimental and theoretical study of the optical absorption spectra of spherical quantum dots based on PbS and PbSe are presented. A rigorous theoretical analysis of the energy spectra and optical transitions is performed within the framework of the four-band k·p approximation with full account of the effect of anisotropy of the band structure. It is shown that strong anisotropy of the band structure of PbS and PbSe leads to the appearance of optical transitions that are forbidden in the isotropic approximation. These transitions were detected in the optical absorption spectra of the investigated quantum dots.