1. Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo. Postal 70-360, Cd. Universitaria México, 04510 D.F., México
2. Fenomenos Nonlineales y Mecánica (FENOMEC), Department of Mathematics and Mechanics, Instituto de Investigación en Matemáticas Aplicádas y Sistemas, Universidad Nacional Autónoma de México, 01000 México D.F., México
3. School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, The King's Buildings, Edinburgh, Scotland EH9 3FD, United Kingdom
4. NooEL Nonlinear Optics and OptoElectronics Lab, University 'Roma Tre,' Via della Vasca Navale 84, 00146 Rome, Italy
5. Optics Lab, Department of Physics, Tampere University of Technology, FI 330101 Tampere, Finland