Nonlinear Optical Properties of the Topological Material Bi₂Se₃ Family for the Application of an Ultrafast Pulse Laser Based on the Occupied and Unoccupied Band Structures

The Bi₂Se₃ family can exhibit many intriguing topological insulator properties, including a narrow bandgap and strong surface states, which show excellent nonlinear optical properties. Thinning bulk Bi₂Se₃ family materials to create a low-cost photoelectric modulation device and explaining the mechanisms of nonlinear optical differences in different types of materials remain challenges. Based on liquid-phase exfoliation technology and tapered fiber, this work prepared optoelectronic modulation devices for various samples within the Bi₂Se₃ family, quantitatively compared their nonlinear optical properties, and analyzed the sources of differentiation using the occupied and unoccupied multiband structure theory. The results correspond well to the phenomena observed in the ultrafast laser, which will provide strong support for the design of higher performance photoelectric devices based on topological insulators.