Ultralow Saturation Intensity Topological Insulator Saturable Absorber for Gigahertz Mode-Locked Solid-State Lasers oleh Yi-Ran Wang, Wei-Heng Sung, Xian-Cui Su, Yue Zhao, Bai-Tao Zhang, Chung-Lung Wu, Guan-Bai He, Yuan-Yao Lin, Hong Liu, Jing-Liang He, Chao-Kuei Lee