[1] Krupke W F 2000 IEEE J. Sel. Top. Quantum Electron. 6
1287

[2] DeLoach L D, Payne S A, Chase L L, Smith L K, Kway W L and Krupke W
F 1993 IEEE J. Quantum Electron. 29 1179

[3] Fan T Y 1993 IEEE J. Quantum Electron. 29 1457

[4] Brown D C 1997 IEEE J. Quantum Electron. 33 861

[5] Lacovara P, Choi H K, Wang C A, Aggarwal R L and Fan T Y 1991
Opt. Lett. 16 1089

[6] Kisel V E, Troshin A E, Tolstik N A, Shcherbitsky V G, Kuleshov N
V, Matrosov V N, Matrosova T A and Kupchenko M I 2004 Opt. Lett.
29 2491

[7] Rivier S, Mateos X, Liu J H, Petrov V, Griebner U, Zorn M, Weyers
M, Zhang H J, Wang J Y and Jiang M H 2006 Opt. Express 14
11668

[8] Kuleshov N V, Lagatsky A A, Shcherbitsky V G, Mikhailov V P,
Heumann E, Jensen T, Diening A and Huber G 1997 Appl. Phys. B 64 409

[9] Lucca A, Jacquemet M, Druon F, Balembois F, Georges P, Camy P,
Doualan J L and Moncorg R 2004 Opt. Lett. 29 1879

[10] Campos S, Denoyer A, Jandl S, Viana B, Vivien D, Loiseau P and
Ferrand B 2004 J. Phys.: Condens. Matter 16 4579

[11] Yang W J, Li J, Zhang F, Zhang Y Y, Zhang Z G, Zhao G J, Zheng L
H, Xu J and Su L B 2007 Opt. Express 15 8486

[12] Li W X, Pan H F, Ding L E, Zeng H P, Zhao G J, Yan C F, Su L B and
Xu J 2006 Opt. Express 14 686

[13] Du J, Liang X Y, Xu Y, Li R X, Zhao G J, Yan C F, Su L B, Xu J and
Xu Z Z 2007 Chin. Opt. Lett. 5 172

[14] Cooke D W, McClellan K J, Bennett B L, Roper J M, Whittaker M T,
Muenchausen R E and Sze R C 2000 J. Appl. Phys. 88 7360

[15] Jie M Y, Zhao G J, Zeng X H, Su L B, Pang H Y, He X M and Xu J
2005 J. Crystal Growth 227 175

[16] Du J, Liang X Y, Xu Y, Li R X, Xu Z Z, Yan C F, Zhao G J, Su L B
and Xu J 2006 Opt. Express 14 3333

[17] Auzel F 1987 Spectroscopy of Solid-State Laser-Type
Materials (New York: Plenum) p 293