1. Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
2. Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China
3. Institute for Advanced Study, Chengdu University, Chengdu, Sichuan 610106, P. R. China
4. State Key Laboratory of Bio-Fibers and Eco-Textiles & College of Physics, University-Industry Joint Center for Ocean Observation and Broadband Communication, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, P. R. China
5. Department of Engineering, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia B2N 5E3, Canada