1. Central European Institute of Technology, Brno University of Technology, Purkyňova 123, Brno, 612 00, Czech Republic
2. Institute of Physical Engineering, Brno University of Technology, Technická 2896/2, Brno, 616 69, Czech Republic
3. Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China
4. Department of Physics, The University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
5. Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
6. Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235-1807, United States