Polaron effects on the third-order nonlinear optical susceptibility in a quantum disk

Theoretical investigation of polaron effects on the third-harmonic generation due to intersubband transition in a quantum disk are presented. Contributions from the bulk longitudinal optical and the surface optical phonon modes are considered separately. The analytic expression for the third-harmonic generation is derived by using the density matrix method. The numerical calculations are performed on a typical GaAs quantum disk with different incident photon energy and under various disk thicknesses. The results demonstrate that the polaron effects are quite important especially around the peak value of the third-order nonlinear optical susceptibility. The maximum χ3ω(3) under the parameters we choose is 7.8×10−16(m/V)2, which is around two order higher than that in the bulk GaAs.