1. College of Information Science and Technology Donghua University Shanghai 201620 P. R. China
2. Liquid Crystals and Photonics Group ELIS Department Ghent University Technologiepark 126 Ghent 9000 Belgium
3. Key Laboratory of Textile Science and Technology Ministry of Education College of Textiles Donghua University Shanghai 201620 P. R. China
4. The Hong Kong University of Science and Technology Hong Kong 99077 P. R. China