[1] [1] J. Durnin, J. J. Miceli Jr., and J. H. Eberly, Phys. Rev. Lett. 58, 1499 (1987).

[2] [2] J. Durnin, J. Opt. Soc. Am. A 4, 651 (1987).

[3] [3] Z. Song, Z. Zhang, and T. Nakajima, Opt. Express 17, 12217 (2009).

[4] [4] Z. Song and T. Nakajima, Opt. Express 18, 12923 (2010).

[5] [5] G. P. Agrawal, Nonlinear Fiber Optics (Academic, San Diego, 1995).

[6] [6] M. Mlejnek, E.M. Wright, and J. V. Moloney, Phys. Rev. E 58, 4903 (1998).

[7] [7] J. E. Rothenberg, Opt. Lett. 17, 583 (1991).

[8] [8] P. Polesana, M. Franco, A. Couairon, D. Faccio, and P. Di Trapani, Phys. Rev. A 77, 043814 (2008).

[9] [9] E. Yablonovitch and N. Bloembergen, Phys. Rev. Lett. 29, 907 (1972).