1. Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
2. Department of Physics, Department of Chemistry, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
3. Instituto Nacional de Metrologia, Qualidade e Tecnologia (Inmetro), Duque de Caxias, RJ 25250-020, Brazil
4. Electrical Engineering Graduate Program, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil