[1] H. M. Pask, R. J. Carman, D. C. Hanna, A. C. Tropper, C. J. Mackechnie, P. R. Barber, and J. M. Dawes, IEEE J. Sel. Top. Quantum Electron. 1, 2 (1995).
[2] V. Dominic, S. MacCormack, R. Waarts, S. Sanders, S. Bicknese, R. Dohle, E. Wolak, P. S. Yeh, and E. Zucker, Electron. Lett. 35, 1158 (1999).
[3] Y. Jeong, J. K. Sahu, S. Baek, C. Alegria, D. B. S. Soh, C. Codemard, and J. Nilsson, Opt. Commun. 234, 315 (2004).
[4] Y. Jeong, J. K. Sahu, D. N. Payne, and J. Nilsson, Elecron. Lett. 40, 470 (2004).
[5] V. Gapontsev and W. Krupke, Laser Focus World 38, 83 (2002).
[6] F. Lv, Y. Fan, H. Wang, and K. Lv, Chin. J. Lasers (in Chinese) 29, 888 (2002).
[7] P. Yan, M. Gong, P. Ou, W. Wei, R. Cui, Q. Liu, and W. Jia, Chin. Opt. Lett. 1, 332 (2003).
[8] J. Zhou, Q.-H. Lou, L.-F. Kong, Z.-L. Wu, D. Xue, J.-X. Dong, Y.-R. Wei, Z.-H. Ye, J.-Q. Zhu, and Z.-J. Wang, Chin. Phys. Lett. 21, 1083 (2004).
[9] I. Kelson and A. A. Hardy, IEEE J. Quantum Electron. 34, 1570 (1998).