Nonlinear optical properties in a strained Zn_xCd _1-xO/Zn_0.1Mg_0.9O quantum dot

Numerical calculations of the excitonic absorption spectra in a strained Zn_xCd_1-xO/Mg_0.1Zn_0.9O quantum dot are investigated for various Cd content taking into account the geometrical confinement. The quantized energies of the exciton as a function of dot radius for various Cd alloy content are computed in a strained Zn_xCd _1-xO/Mg_0.1Zn_0.9O quantum dot and thereby the interband emission energy is calculated considering the internal electric field induced by the spontaneous and piezoelectric polarizations. The nonlinear optical properties such as optical absorption and the changes of refractive index as a function of photon energy for various values of Cd alloy content and the optical intensities are discussed. Increase of exciton binding energy and the corresponding optical band gap with the Zn content imply that the confinement of carriers increases with composition x. The main results show that the confined energies and the transition energies between the excited levels are significant for smaller dots. Non-linearity band gap with the increase in Zn content is observed for smaller dots in the strong confinement region and the magnitude of the absorption spectra increases for the transitions between the higher excited levels.