[1] P. Yankov, J. Phys. D 27, 1118 (1994).
[2] J. J. Zayhowski and C. Dill, Opt. Lett. 19, 1427 (1994).
[3] W. Chen, K. Spariosu, and R. Stultz, Opt. Commun. 104, 71 (1993).
[4] Y. K. Kuo, M. F. Huang, and M. Birnbaum, J. Quantum Electron. 31, 657 (1995).
[5] W. Kochner, Solid State Laser Engineering (Springer, Berlin, 1992) p. 489.
[6] J. A. Morris and C. R. Pollock, Opt. Lett. 15, 440 (1990).
[7] J. Dong, P. Z. Deng, Y. H. Zhang, Y. P. Liu, J. Xun, and W. Chen, Opt. Lett. 25, 1101 (2000).
[8] X. D. Xu, Z. W. Zhao, J. Xu, and P. Z. Deng, J. Cryst. Growth 225, 272 (2003).
[9] J. Dong, P. Z. Deng, Y. H. Zhang, Y. P. Liu, J. Xun, and W. Chen, Appl. Opt. 40, 4303 (2001).
[10] J. Dong, P. Z. Deng, Y. P Liu, Y. H. Zhang, G. S. Huang, and F. X. Gan, Chin. Phys. Lett. 19, 342 (2002).
[11] S. A. Markgraf, M. F. Pangborn, and R. Dieckmann, J. Cryst. Growth 180, 81 (1997).
[13] R. Feldman, Y. Shimony, and Z. Burshtein, Opt. Mater. 24, 333 (2003).
