ZnO团簇的非线性光学特性

he luminescent properties of ZnO clusters remain unexplored although they are known to possess strong surface effects and a large number of surface defect levels. By using fluorescence spectrometer and femtosecond laser, we invesigated the luminescence of ZnO clusters under single-photon and multiphoton excitation and the underlying phsyical mechanism. When the excitation wavelength was chosen to be 360 nm, the strangest luminescence intensity was osberved. However, the luminescence intensity decreased gradually and the emission peak was red shifted with increasing excitation wavelength. When the excitation wavelength was chosen to be 780 nm, the luminescnce peak appeared at ~490 nm and the luminescence intensity increased nonlinearly with increasing excitation intensity. As an example of practical applicastion, we demonstrated that ZnO clusters could be used in the imaging of living cells under two-photon excitation.