[1] Stokowski S E, et al. Growth and characterization of large Nd, Cr:GSGG crystals for high-average-power slab lasers [J]. IEEE J. Quantum Electronics, 1988, 24(6): 934-948.

[2] Dinerman B J, Moulton P F. Up-conversion luminescence of Er3+ yttrium [C]. Proceedings of IEEE LEOS’92 Annual Meeting, 1992, 310-311.

[4] Judd B R. Optical absorption intensities of rare-earth ions [J]. Phys. Rev., 1962, 127(3): 750-761.

[5] Ofelt G S. Intensities of crystal spectra of rare-earth ions [J]. J. Chem. Phys., 1962, 37(3): 511-520.

[6] Carnall W T, Field P R, Rajnak K. Electronic energy levels in the trivalent lanthanide aquaions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+ [J]. J. Chem. Phys., 1968, 49: 4424-4442.

[7] Weber M J. CRC Handbook of Laser Science and Technology VolI. Section1: Applications [M]. CRC Press, 1987.

[8] Sardar D K, Bradley W M, Perez J J, et al. Judd-Ofelt analysis of the Er3+ (4f11) absorption intensities in Er3+-doped garnets [J]. Journal of Applied Physics, 2003, 93(5): 2602-2607.

[9] Li C, Guyot Y, Linatès C, et al. Radiative transition probabilities of trivalent rare-earth ions in LiYF4 [C]. OSA Proceedings on Advnnced Solid-State Lasers, 1993, 15: 91-95.

[10] Kumar G A, Riman R, Chae S C, et al. Synthesis and spectroscopic characterization of CaF2:Er3+ single crystal for highly efficient 1.53 μm amplification [J]. Journal of Applied Physics, 2004, 95(7): 3243-3249.

[11] Serban Georgescu, Octavian Toma, Totia H. Intrinsic limits of the efficiency of erbium 3 μm lasers [J]. IEEE J. Quantum Electronics, 2003, 39(6): 722-732.

[12] Zhekov V I, Murina T M, Prokhorov A M, et al. Cooperative processes in Y3Al5O12:Er3+ crystal [J]. Kvantovaya Elektronika, 1986, 13(2): 419-422.