Efficient multiphoton-absorption-induced luminescence in single-crystalline ZnO at room temperature.

At room temperature, multiphoton absorption- (MPA-) induced photoluminescence in ZnO strongly driven by a femtosecond (fs) near-infrared laser is studied. Two-photon absorption and three-photon absorption are proved to be responsible for the intense luminescence, when the wavelength of the fs excitation laser is above and below the half-bandgap of ZnO, respectively. Strong MPA absorption in ZnO is unambiguously evidenced by the interferometric autocorrelation measurements of the luminescence signal.