Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation

Room-temperature ultraviolet emission of Tm3+ ions at 298 (I-1(6) -> H-3(6)), 364 (D-1(2) -> H-3(6)), and 391 nm (I-1(6) -> H-3(5)) was obtained in Y2O3:Yb3+-TM3+ by continuous-wave diode laser excitation of 980 nm. Power dependence analysis demonstrates that five- and six-photon upconversion processes populate the D-1(2) and I-1(6) states, respectively. We believe that the D-1(2) population originates from the cross relaxation (1)G(4) + F-3(4) -> H-3(4) + D-1(2) of the TM3+ ions, while subsequent energy transfer from Yb3+ to Tm3+ excites the D-1(2) state to the upper I-1(6) state. High multiphoton-induced ultraviolet emission is also expected for other trivalent rare-earth ions similar to Tm3+. (c) 2006 Optical Society of America