Laboratory of Telecommunications and Materials Science and Engineering-www.locem.ufc.br-Fortaleza, Ceará, Brazil;
Department of Physics, Science Center, Federal University of Ceará(U.F.C.)-Fortaleza, Ceará, Brazil;
State University of Vale do Acaraú, Sobral, Ceará, Brasil;
Laboratory of Telecommunications and Materials Science and Engineering-www.locem.ufc.br-Fortaleza, Ceará, Brazil;
Department of Physics, Science Center, Federal University of Ceará(U.F.C.)-Fortaleza, Ceará, Brazil;