[1] P. Gill, Metrologia 42, s125 (2005).

[2] S. A. Diddams, J. C. Bergquist, S. R. Jefferts, and C. W. Oates, Science 306, 1318 (2004).

[3] T. Quinn, Metrologia 30, 523 (1994).

[4] D. Xu, J. Yao, L. Guo, R. Zhou, B. Zhang, X. Ding, L. Wen, and P. Wang, Acta Opt. Sin. (in Chinese) 24, 925 (2004).

[5] Z. Yao, J. Jiang, B. Tu, T. Zhou, and L. Chui, Chinese J. Lasers (in Chinese) 32, 1459 (2005).

[6] Q. Zhen, L. Zhao, and S. Dong, Chinese J. Lasers (in Chinese) 31, 1030 (2004).

[7] G. D. Boyd and D. A. Kleinman, J. Appl. Phys. 39, 3579 (1968).

[8] J. Zhang, H. Ma, Y. Luo, H. Tao, K. Zhang, and C. Peng, Chinese J. Lasers (in Chinese) 29, 1057 (2002).

[9] X. Wang, J. Chen, G. Li, and T. Zuo, Acta Opt. Sin. (in Chinese) 24, 477 (2004).

[10] D. A. Manoel, R. L. Cavasso-Filho, A. Scalabrin, D. Pereira, and F. C. Cruz, Opt. Commun. 201, 157 (2002).

[11] C. W. Oates, F. Bonde, R. W. Fox, and L. Hollberg, Eur. Phys. J. D 7, 449 (1999).

[12] F. Riehle, H. Schnatz, B. Lipphardt, G. Zinner, T. Trebst, and J. Helmcke, IEEE Trans. Instrument. Measur. 48, 613 (1999).

[13] J. Grünert, Ultracold Metastable Calcium Atoms In a Bichromatic Magneto-optical Trap PhD thesis, des Fachbereichs Physik, der Universitat Hambrug (2002).

[14] Z. Wang, B. Teng, X. Xu, K. Fu, B. Xu, J. Wang, and Z. Shao, Acta Phys. Sin. (in Chinese) 52, 2176 (2003).

[15] T. W. Hamsch and B. Couillaud, Opt. Commun. 35, 441 (1980).