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Nonlinear Photoluminescence from ZnO Nanobelts

The nonlinear photoluminescence (PL) including second-harmonic generation (SHG) and the multiphoton luminescence (MPL) around 385 nm and 530 nm 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.