Magnetic Topological Insulator MnBi<sub>2</sub>Te<sub>4</sub> Nanosheets for Femtosecond Pulse Generation
Haiqin Deng, Yan Zhang, Xiaoxin Yang, Qiang Yu, Pengdong Wang, Zixin Yang, Yongping Dai, Xiuyang Pang, Xiao Wang, Jian Wu, Pu Zhou
Abstract
The van der Waals layered material MnBi 2 Te 4, as a magnetic topological insulator, has attracted tremendous interest for novel physics research in the fields of condensed matter physics and materials science. However, the nonlinear optical properties of MnBi 2 Te 4 and its applications in ultrafast optics have rarely been explored. In this study, high-quality MnBi 2 Te 4 nanosheets have been successfully synthesized by the self-flux method. The morphology, chemical composition, magnetic properties, and nonlinear optical characteristics were systematically investigated. The magnetic transition of MnBi 2 Te 4 was confirmed by a low-temperature spatially resolved spectroscopic technique. The saturable absorption property of MnBi 2 Te 4 was measured by a balanced twin-detector system with a modulation depth of 4.5% and a saturation optical intensity of 2.35 GW/cm 2 . Furthermore, by inserting the MnBi 2 Te 4 -based saturable absorber, a soliton mode-locking laser operating at 1558.8 nm was obtained with a pulse duration of 331 fs. This research will pave the way for applications of the magnetic TI MnBi 2 Te 4 in nonlinear optics and photonics.