Few-layer bismuthene is an emerging two-dimensional material in the fields of physics, chemistry, and material science. However, its nonlinear optical property and the related photonics device have been seldom studied so far. Here, we demonstrate a sub-200 fs soliton mode-locked erbium-doped fiber laser (EDFL) using a microfiber-based bismuthene saturable absorber for the first time, to the best of our knowledge. The bismuthene nanosheets are synthesized by the sonochemical exfoliation method and transferred onto the taper region of a microfiber by the optical deposition method. Stable soliton pulses centered at 1561 nm with the shortest pulse duration of about 193 fs were obtained. Our findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.

Due to the unique properties of two‐dimensional (2D) materials, much attention has been paid to the exploration and application of 2D materials. In this review, we focus on the application of 2D materials in mode‐locked fiber lasers. We summarize the synthesis methods for 2D materials, fiber integration with 2D materials and 2D materials based saturable absorbers. We discuss the performance of the diverse mode‐locked fiber lasers in the typical operating wavelength such as 1, 1.5, 2 and 3 μm. Finally, a summary and outlook of the further applications of the new materials in mode‐locked fiber lasers are presented.