1. Lehrstuhl für Laser- und Röntgenphysik, Physik-Department, TUM School of Natural Sciences, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany
2. Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, 21 Nanyang Link, 637371, Singapore
3. Interdisciplinary Graduate School, Energy Research Institute @NTU (ERI@N), Nanyang Technological University, 50 Nanyang Drive, 637553, Singapore
4. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, P. R. China
5. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371, Singapore