1. Forschungszentrum Dresden-Rossendorf, PF 510 119, 01314 Dresden, Germany
2. Institute of Photoelectronics, Nankai University, Tianjin 300071, China
3. Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
4. FHR Anlagenbau GmbH, 01458 Ottendorf-Okrilla, Germany