1. National Council of Science and Technology (CONACYT), Av. Insurgentes Sur 1582, Col. Crédito Constructor del Benito Juárez, C.P. 03940, Cd. de Mexico, Mexico.
2. Department of Physics and Mathematics, Institute of Engineering and Technology, Universidad Autónoma de Ciudad Juárez, Av. del Charro 450 Col. Romero Partido, C.P. 32310, Juárez, Chihuahua, Mexico.