1. Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE School of Physical Science and Technology Lanzhou University Lanzhou Gansu 730000 China
2. Integrated Photonics and Applications Centre (InPAC) School of Engineering RMIT University Melbourne VIC 3001 Australia
3. Ligentec SA Ecublens 1024 Switzerland
4. The State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai 200240 China