Blue, green and 0.8 mu m Tm3+, Ho3+ doped upconversion laser glasses, sensitized by Yb3+

To obtain efficient upconversion laser glass, the optical properties of Tm3+ and Ho3+ were investigated in various glasses, Fluoride glass was selected as base glass for upconversion. The efficient upconversion fluorescences corresponding to the (1)G(4) --> H-3(6) and F-3(4) --> H-3(6) transitions of Tm3+ and the S-5(2) --> I-5(8) transition of Ho3+ were observed in Yb3+-Tm3+ and Yb3+-Ho3+ doped aluminozircofluoride glasses excited at 980 nm. The very stronge blue and green emission light can be observed visually. The upconversion processes observed were two-photon processes for F-3(4) --> H-3(6), S-5(2) --> I-5(8) transitions and three-photon processes for the (1)G(4) --> H-3(6) transition and can be described by a rate equation model. The energy transfer and energy back-transfer were analyzed in Yb3+-Tm3+ and Yb3+-Ho3+ systems. The relationship between emission intensity, pumping intensity and dopant concentrations is described using a rate equation model and shows good agreement with experiments. The dynamics of excited state (Yb3+2F5/2) is also analyzed with the diffusion-limited model based on Yokota-Tanimoto theory.