Theoretical investigation on the third order nonlinear optical susceptibility in CdS/ZnS/CdS/ZnS core/shell/well/shell quantum dots for optoelectronic applications

In this paper, a detailed study on the third order nonlinear optical susceptibility for quadratic electro-optic effects for CdS/ZnS/CdS/ZnS core/shell/well/shell spherical quantum dots is realized. Electron energies and corresponding functions are investigated under the frame work of the effective-mass approximation. Then, the third order nonlinear susceptibility is determined using the density matrix method. The dot size effect on this susceptibility is also examined. Numerical calculations confirm that both position and intensity of the peaks can be controlled by varying shell thickness. In addition, by increasing the width of inner or outer shell, the peaks of susceptibility is redshifted and the intensities are increased. Moreover, the 'inverted' structure, ZnS/CdS/ZnS/CdS has shown better nonlinear optical properties.