[1] Institute of Physics, Academia Sinica, Taipei 115, Taiwan
[2] Department of Physics, National Taiwan University, Taipei 106, Taiwan
[3] Department of Physics, Fu Jen Catholic University, Taipei 242, Taiwan
[4] Unit Mixte de Physique CNRS/Thales, 91767 Palaiseau, Cedex, France
[5] Universit Paris-Sud 11, Orsay 91405, France
[6] Laboratoire de Photonique et de Nanostructure, CNRS, F-91460 Marcoussis, France