Influence of the position of a donor impurity on the second-order nonlinear optical susceptibility in a cylindrical quantum dot

The second-order nonlinear optical susceptibility in a cylindrical quantum dot (CQD) of GaAs/Ga0.6Al0.4As with a donor impurity inside under the influence of a uniform magnetic field applied in the axial direction of the cylinder is studied theoretically. Using the variational method, the energies and the wave functions of the 1S−like,2P−−like, and 2P+−like impurity states were found when it moves inside of the CQD. It was found that there is a degeneration of the energy of the impurity for the 2P−−like and 2P+−like states in the absence of magnetic field, producing two resonant peaks for the second-harmonic generation (SHG) for any position of the impurity. This degeneration is split only when a magnetic field is applied, indicating a Zeeman effect in the system. Thus the variation of the intensity of the magnetic field allows tuning the condition of resonance of two photons. It was also found that the increase in the radial position of the impurity produces an increase in the intensity of the peaks of the optical rectification (OR) and SHG coefficients, therefore a variation of the position of the impurity in a CQD allows modulating the intensity of the second-order nonlinear optical response.