Optical Nonlinearity and Enhanced Second Harmonic Generation in Copper–doped Cadmium Iodide Nanocrystals

Cadmium iodide nanocrystals are grown and doping defect and quantum-confinement effects in optical susceptibility in the nanocrystals are investigated. The nanomaterials with various crystal sizes are pumped with intense laser beams. This pump-probe experiment probes the doubled-frequency second harmonic generation (SHG). The second–order optical susceptibility is calculated from the experimentally measured SHG intensity. The results show that a significant enhancement in the optical susceptibility is achieved in nanomaterials with moderate doping. However, bulk and intrinsic crystals show no considerable SHG effect. The results were discussed within models of the impurity induced metallic-aggregators and photoinduced electron-phonon anharmonic interactions.