[1] Xu X Y et al 2003 Phys. Rev. Lett. 90 193002

[2] Zhao P Y et al 2008 Chin. Phys. Lett. 25 3631

[3] Katori H et al 1999 Phys. Rev. Lett. 82 1116

[4] Udem T et al 2001 Phys. Rev. Lett. 86 4996

[5] Zinner G et al 2000 Phys. Rev. Lett. 85 2292

[6] Xu X Y et al 2003 J. Opt. Soc. Am. B 20 968

[7] Chaneliere T et al 2005 J. Opt. Soc. Am. B 22
1819

[8] Takamoto M, Hong F L, Higashi R and Katori H 2005
Nature 435 7040

[9] Wang S K, Zhang Y Y, Lin B K, Wang M M and Fang Z J 2008
Proceedings of the Conference on Precision Electromagnetic
Measurement (Broomfield, Colorado, USA 8--13 June 2008) p 316

[10] Loftus T H, Ido T, Boyd M M, Ludlow A D and Ye J 2004
Phys. Rev. A 70 063413

[11] Maruyama R 2003 PhD thesis (University of
Washington)

[12] Xu X Y Loftus T H, Smith M J, Hall J L, Gallagher A and
Ye J 2002 Phys. Rev. A 66 011401

[13] Weiss D S et al 1989 J. Opt. Soc. Am. B 6
2072

[14] Dedman C J et al 2004 Rev. Sci. Instrum. 75
5136

[15] Wieman C E and Hollberg L 1991 Rev. Sci. Instrum.
62\,1

[16] Sorrentino Ferrari G, Poli N, Drullinger R and Tino G M
2006 arXiv:physics. 0609133