[1] Linkoping Univ, Dept Elect Engn, S-58183 Linkoping, Sweden
[2] Nanjing Univ, Natl Lab Solid State Microstruct, Nanjing, Peoples R China
[3] Linkoping Univ, Dept Phys Chem & Biol, S-58183 Linkoping, Sweden
[4] Univ Concepcion, Dept Phys, Concepcion, Chile
[5] Millennium Inst Res Opt, Concepcion, Chile