1. School of Electrical Engineering and Computer Science/Department of Physics and Photon Science, Gwangju Institute of Science and Technology, 123 Chemdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea
2. Laser R&D Laboratory, LIG Nex1, 207 Mabuk-ro, Giheung-gu, Yongin-si, Gyeonggi-do 16911, Republic of Korea
3. Nano-Photonics Research Center, Korea Photonics Technology Institute, 9 Chemdanventure-ro, 108 Beon-gil, Buk-gu, Gwangju 61007, Republic of Korea
4. Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA