[1] J. Vanier and C. Audoin, The Quantum Physics of Atomic Frequency Standards (Adam-Hilger, Bristol, 1989).

[2] J. Vanier, Appl. Phys. B: Lasers and Optics 81, 421 (2005).

[3] G. S. Pati, F. K. Fatemi, and M. S. Shahriar, Opt. Express 19, 22388 (2011).

[4] A. Godone, S Micalizio, and F Levi, Phys. Rev. A 70, 023409 (2004).

[5] T. Zanon, S. Guerandel, E. De Clercq, and D. Holleville, Phys. Rev. Lett, 94, 193002 (2005).

[6] B. Yan, Y. Ma, and Y. Wang, Phys. Rev. A 79, 063820 (2009).

[7] C. Deutsch, F. Ramirez-Martinez, C. Lacroute, F. Reinhard, T. Schneider, J. N. Fuchs, F. Piechon, F. Laloe, J. Reichel, and P. Rosenbusch, Phys. Rev. Lett 105, 020401 (2010).

[8] M. D. Lukin, S. F Yelin, M. Fleischhauer, and M. O. Scully, Phys. Rev. A 60, 3225 (1999).

[9] Y.-C. Chen, Y.-A. Liao, H.-Y. Chiu, J.-J. Su, and I. A. Yu, Phys. Rev. A 64, 053806 (2001).

[10] Y. Niu, S. Gong, R. Li, Z. Xu, and X. Liang, Opt. Lett. 30, 3371 (2005).

[11] W. Hanle, Z. Phys. 30, 93 (1924).

[12] Y. Li and M. Xiao, Opt. Lett. 20, 1489 (1995).

[13] H. X. Chen, A. V. Durrant, J. P. Marangos, and J. A. Vaccaro, Phys. Rev. A 58, 1545 (1998).

[14] S. J, Park, H. Cho, T. Y. Kwon, and H. S. Lee, Phys. Rev. A 58, 023806 (2004).