Ultrafast pulse generation via magnetic topological insulator MnBi2Te4 nanosheets

Recently, 2D layered MnBi2Te4 has been a promising candidate for discovering the exotic topological quantum phenomena for the coexisting topology and magnetism. In particular, the layered structure of MnBi2Te4 with a small bandgap possesses excellent ultrafast nonlinear response and broadband saturable absorption, which indicates that they can be applied in the field of ultrafast photonics. Despite tremendous research on magnetism and topology, the nonlinear optical properties of MnBi2Te4 have been underexplored. Herein, we have successfully synthesized the high-quality MnBi2Te4 by the self-flux method. By using MnBi2Te4 nanosheets as a saturable absorber (SA), a passive mode-locking erbium-doped fiber (EDF) laser centered at 1560 nm was obtained with a pulse duration of 331 fs. This work suggests that magnetic topological insulators possess great potential for ultrafast photonics.