2Biswas A, Maciel G S, Friend C S, et al. Upconversion properties of a transparent Er^3+-yb^3+ co-doped LaF3-SiO2 glass-ceramics prepared by sol-gel method. J Non-Cryst Solids, 2003, 316(2-3): 393-397
3Martin I R, Mendez-Ramos J, Rodriguez V D, et al. Increase of the 800 nm excited Tm^3+ blue upconversion emission in fluoroindate glasses by codoping with Yb^3+ ions. Opt Mater, 2003, 22(4): 327-333
4Li S F, Zhang Q Y, Lee Y P. Absorption and photoluminescence properties of Er-doped and Er/Yb codoped soda-silicate laser glasses. J Appl Phys, 2004, 96(9): 4746-4750
5Noginov M A, Curley M, Venkateswariu P, et al. Excitation scheme for the upper energy levels in a Tm:Yb:BaY2F8 laser crystal. J Opt Soc Am B, 1997, 14(8): 2126-2137
6Hehlen M P, Kuditcher A, Lenef A L, et al. Nonradiative dynamics of avalanche upconversion in Tm: LiYF4. Phys Rev B, 2000, 61:1116-1128
7Reisfeld R. Lasers and Excited States of Rare-Earth. New York: Springer-Verlag, 1977
8Auzel F. Upconversion and anti-stokes processes with land dions in solids. Chem Rev, 2004, 104(1): 141-173
9Downing E, Hesselink L, Ralston J, et al. A three-color, solid-state, three-dimensional display. Science, 1996, 273(5279): 1185-1187
10Balda R, Garcia-Adeva A J, Voda M, et al. Upconversion processes in Er^3+-doped KPb2Cl5. Phys Rev B, 2004, 69(20): 205203
