[1] [1] Cheo P K, King G G. Clad-pump Yb∶Er codoped fiber laser.IEEE Photonics Technology Letters,2001,13(3):188～190

[2] [2] Dominic V, Maccormack S,Waarts R,et al. 110 W fiber laser. Electron Lett,1999,35(14):1158～1159

[3] [3] Miyazaki T,Inagaki K,Karasawa Y,et al. Nd-doped double-clad fiber amplifier at 1.06 μm.Journal of Lightwave Technology,1998,16(4):562～566

[4] [4] Zellmer H,Plamann K,Huber G. Visible double-clad upconversion fiber laser. Electron Letter,1998,34(6): 565～567

[5] [5] Pask H M, Carman R J, Hanna D C,et al. Ytterbium-doped silica fiber lasers: versatile sources for the 1.2 μm region.IEEE Journal of Selected Topics in Quantum Electronics,1995,1(1):2～3

[6] [6] Nakazawa E. Shionoya S.Cooperative Luminescence in YbPO4.Phys Rev Lett,1970,25(24):1710～1712

[8] [8] Magne S, Ouerdane Y, Druetta M, et al. Cooperative luminescence in an ytterbium-doped silica fiber.Optics Communication, 1994,111(3～4):310～316

[9] [9] Fujii M,Hayashi S,Yamaoto K. Excitation of intra-4f shell luminescence of Yb3+ by energy tranfer from Si nanocrystals.Applied Physics Letters,1998,73(21):3108～3110

[10] [10] Auzel F, Meichenina D, Pellé F,et al. Cooperative luminescence as a defining process for RE-ions clustering in glasses and crystals.Optical Materials, 1994,4(1): 35～41