The third-order nonlinear optical susceptibility of the quantum dot as a three-level system in a hybrid structure

To increase the optical nonlinearity effects in hybrid structures comprising a quantum dot and a nanoparticle, a quantum dot is taken as a three-level system. Under the dipole–dipole interactions between the quantum dot and the nanoparticle, the density matrix elements are derived within the rotating approximation. Under the quasi-static approximation by taking the nanoparticle polarization as a function of its geometry, the induced fields around the quantum dot in the presence of one/two nanoparticle(s) are obtained and the increasing factors of the local fields are calculated. The third-order nonlinear optical susceptibility of quantum dot is achieved by using the perturbation expansion theory of density matrix for different geometries of the nanoparticle, and the effects of the structural parameters are investigated to optimize the nonlinear optical response of the system. It can be seen that the presence of two nanorods results in great optical nonlinearities in the hybrid structure, being suitable for on/off switches, quantum communication, and quantum computing applications.