ACKNOWLEDGMENTS This research was funded by Ministerio de Ciencia e Innovaci´ on (MICIIN) under the project TEC2009-11635. [1] J. Durnin, J. Opt. Soc. Am. A 4 , 651 (1987). [2] J. Durnin, J. J. Miceli, and J. H. Eberly, Phys. Rev. Lett. 58 , 1499 (1987). [3] Localized Waves , edited by H. E. Hern´ andez-Figueroa, M. Zamboni-Rached, and E. Recami (John Wiley & Sons, 2008). [4] G. Indebetouw, J. Opt. Soc. Am. A 6 , 150 (1989). [5] J. Fagerholm, A. T. Friberg, J. Huttunen, D. P. Morgan, and M. M. Salomaa, Phys. Rev. E 54 , 4347 (1996). [6] D. Mugnai, A. Ranfagni, and R. Ruggeri, Phys. Rev. Lett. 84 , 4830 (2000). [7] S. Longhi, K. Janner, and P. Laporta, J. Opt. B 6 , 477 (2004). [8] A. V. Novitsky and D. V. Novitsky, J. Phys. A: Math. Gen. 39 , 5227 (2006). [9] C. J. Zapata-Rodr´ıguez, M. A. Porras, and J. J. Miret, J. Opt. Soc. Am. A 25 , 2758 (2008). [10] C. J. Zapata-Rodr´ıguez and J. J. Miret, arXiv:0910.5642v1 [physics.optics](2009). [11] J. J. Miret and C. J. Zapata-Rodr´ıguez, J. Opt. Soc. Am. B 25 , 1 (2008). [12] D. N. Christodoulides, F. Lederer, and Y. Silberberg, Nature 424 , 817 (2003). [13] O. Manela, M. Segev, and D. N. Christodoulides, Opt. Lett. 30 , 2611 (2005). [14] K. Staliunas and R. Herrero, Phys. Rev. E 73 , 016601 (2006). [15] Z. Bouchal and M. Olivik, J. Mod. Opt. 45 , 1555 (1995). [16] Z. Bouchal, J. Bajer, and M. Bertolotti, J. Opt. Soc. Am. A 15 , 2172 (1998). [17] P. P¨ a¨ akk¨ onen, J. Tervo, P. Vahimaa, J. Turunen, and F. Gori, Opt. Express 10 , 949 (2002). [18] J. D. Joannopoulos, S. G. Johnson, J. N. Winn, and R. D. Meade, Photonic crystals. Molding the flow of light (Princeton University Press, 2008). [19] S. A. Ramakrishna and O. J. F. Martin, Opt. Lett. 30 , 2626 (2004). [20] L. D. Landau, E. M. Lifshitz, and L. P. Pitaevskii, Electrodynamics of continuous media (Butterworth-Heinenann, Oxford, England, 1984). [21] P. Yeh, Optical Waves in Layered Media (Wiley, New York, 1988). 18