Nonlinear Photoluminescence from ZnO Nanobelts

The nonlinear photoluminescence (PL) including second-harmonic generation (SHG) and the multiphoton luminescence (MPL) around 385nm and 530nm from ZnO nanobelts are investigated by using near-infrared excitations. The excitation wavelength dependence of MPL intensity reveals resonant energy transfer from SHG to MPL near the band gap excitation. The lifetime measurement of the MPL shows a much slower decay process of the defect emission, which results from the generation and recombination of both donors and acceptors on the disordered surface of the ZnO nanobelts.