Electric field effect on the third-order nonlinear optical susceptibility in inverted core-shell nanodots with dielectric confinement

Third-order nonlinear optical processes associated with the interlevel transitions in ZnS/CdSe core-shell quantum dots under electric fields are theoretically investigated. Taking into account the dielectric mismatch with the surrounding matrix, the electronic structure of the dots is obtained within the effective mass and parabolic band approximations. It is shown that large applied electric fields break the symmetry of the confinement potential and lead to a significant blue-shift of the peak positions in the nonlinear optical spectrum. The size effect is also discussed and it is proved that large nonlinear susceptibility can be obtained by increasing the thickness of the nanocrystal shell. Our results suggest that external factors such as the applied electric field and orientation of the incident light polarization can be used - in addition to spatial confinement - to improve the performances of the optical devices.