Energy spectra and the third-order nonlinear optical properties in GaAs/AlGaAs core/shell quantum dots with a hydrogenic impurity

摘要

The energy levels and binding energies of hydrogenic impurity associated with the ground state and some low-lying states in GaAs/AlGaAs core/shell quantum dots are theoretically studied by using the finite difference method. It is shown that energy levels and binding energies are depended dramatically on the size of the quantum dot due to quantum size effect. The change of the level ordering for hydrogenic impurity can be found and then to cause the corresponding changes in the binding energies, which can be adjusted by the radius of the quantum dot. Based on the analysis of these energy levels, the third-harmonic generation susceptibility in this quantum dot with (or without) impurity is investigated by using the compact-density-matrix approach. The results show that the third harmonic generation susceptibility obtained in the two cases can reach the magnitude of ～10~(-7) m~2 V~(-2) by choosing a large radius of quantum dot. For the large quantum dot with impurity, it is found that the third-harmonic generation susceptibility can be effectively enhanced about 1.3 ～ 1.5 times than the case regardless of the impurity. Finally, the resonant peak and its corresponding to resonant energy are also taken into account.