1. Université de Haute-Alsace; CNRS; Institut de Science des Matériaux de Mulhouse; IS2M UMR 7361, 15 rue Jean Starcky F 68100 Mulhouse France
2. Université de Strasbourg; 4 rue Blaise Pascal CS 90032 F-67081 Strasbourg cedex France
3. Department of Photonics; College of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu Taiwan 30010 Republic of China