Difference frequency generation in CdSe quantum dots: the effect of conduction band nonparabolicity

We investigate the difference frequency generation (DFG) in a singly charged CdSe quantum dot with ZnS, ZnSe, MgS, and MgSe as confining barriers. Calculations are performed with the inclusion of the nonparabolic nature of the conduction band. Considering intersublevel transitions within the conduction band, the discrete energy states and corresponding wave functions are determined by solving the three-dimensional Schrödinger equation under the effective mass approximation. The influence of band nonparabolicity is incorporated through Kane’s model. Employing the density matrix framework, we evaluate the second-order susceptibility coefficients governing the DFG process. For CdSe/ZnS, CdSe/ZnSe, CdSe/MgSe, and CdSe/MgS quantum dots, the nonlinear susceptibility with the inclusion of nonparabolicity of conduction band is enhanced as compared to that without the inclusion of conduction band nonparabolicity. Moreover, the efficiency of DFG is shown to be sensitive to the nonparabolicity-dependent transition energies, transition dipole matrix moments, local field factor, dot size, polarization state of the incident photons, and the surrounding barrier material.