[1] Yamada M, Ono H and Ohishi Y 1998 Electron. Lett. 34
1490

[2] Fujimoto Y and Nakatsuka M 2001 Jpn. J. Appl. Phys. 40
L279

[3] Fujimoto Y and Nakatsuka M 2003 Appl. Phys. Lett. 82
3325

[4] Peng M Y, Qiu J R, Chen D P, Meng X G and Zhu C S 2005 Opt.
Lett. 30 2433

[5] Peng M Y, Qiu J R, Chen D P, Meng X G and Zhu C S 2005 Opt.
Express 13 6892

[6] Meng X G, Qiu J R, Peng M Y, Chen D P, Zhao Q Z, Jiang X W and Zhu
C S 2005 Opt. Express 13 1628

[7] Meng X G, Qiu J R, Peng M Y, Chen D P, Zhao Q Z, Jiang X W and Zhu
C S 2005 Opt. Express 13 1635

[8] Ren J J, Qiu J R, Chen D P, Zhao Q Z, Jiang X W and Zhu C S 2007
Solid. State. Commun. 141 559

[9] Dvoyrin V V, Mashinsky V M, Bulatov L I, Bufetov I A, Shubin A V,
Melkumov M A, Kustov E F, Dianov E M, Umnikov A A, Khopin V F,
Yashkov M V and Guryanov A N 2006 Opt. Lett. 31 2966

[10] Dvoyrin V V, Mashinsky V M and Dianov E M 2007 Opt. Lett.
32 451

[11] Razdobreev I, Bigot L, Pureur V, Favre A, Bouwmans G and Douay M
2007 Appl. Phys. Lett. 90 031103

[12] Ren J, Chen D P, Yang G, Xu Y S, Zeng H D and Chen G R 2007
Chin. Phys. Lett. 24 1958

[13] Dong G P, Tao H Z, Xiao X D, Lin C G, Gong Y Q, Zhao X J, Chu S S,
Wang S F and Gong Q H 2007 Opt. Express 15 2399

[14] Dong G P, Tao H Z, Xiao X D, Lin C G, Zhao X J and Mao S 2007
J. Phys. Chem. Solids 68 158

[15] Tao H Z, Zhao X J, Jing C B, Yang H and Mao S 2005 Solid.
State. Commun. 133 327

[16] Peng M Y, Meng X G, Qiu J R, Zhao Q Z and Zhu C S 2005 Chem.
Phys. Lett. 403 410

[17] Voynarovych I, Pinzenik V, Makauz I, Shiplyak M, Kokenyesi S and
Daroczi L 2007 J. Non-Cryst. Solids 353 1478

[18] Heo J, Joong M Y and Ryou S Y 1998 J. Non-Cryst. Solids
238 115

[19] Griffiths J E, Philips J C, Espinosa G P and Remeika J P 1982
Phys. Rev. B 26 3499

[20] Blasse G, Meijerink A, Nomes M and Zuidema J 1994 J. Phys.
Chem. Solids 55 171

[21] Elliott S R and Steel A T 1986 Phys. Rev. Lett. 57
1316

[22] Mytilineou E, Chao B S and Papadimitriou D 1996 J. Non-Cryst.
Solids 195 279