Nonlinear absorption in semiconductor quantum dots

The density matrix approach has been employed to understand the mechanism of nonlinear absorption / gain in a single semiconductor quantum dot as well as in an inhomogeneous distribution of quantum dots. The analytical results show an enhancement of excitonic gain in the presence of biexcitons. The same has been confirmed by the numerical analysis carried out for a realistic system of semiconductor quantum dots of CdS embedded in a glass matrix. The numerical study exhibits a red shift of maximum gain at large distribution widths.