Preparation of High Damage Threshold Device Based on Bi₂Se₃ Film and Its Application in Fiber Lasers

As a handicap for passive mode-locked lasers to operate stably for a long time, the undesirable damage threshold of saturable absorption devices means that it is difficult to maintain a normal operation state under the irradiation brought by ultrashort pulses. To reduce the damage probability when the saturable absorption devices interact with an ultrafast laser, some technologies have been developed to resist the high-energy irradiation of an ultrafast laser that will also increase the difficulty of laser construction at the same time. In this paper we put forward a new research idea to improve the low-damage threshold problem: optimizing the optical transmittance, which will avoid dissociation due to excessive heat accumulation. Using the melt and machine exfoliation method, the high optical transmittance (>95%) saturable absorption devices based on Bi₂Se₃ are prepared, whose damage threshold (2.45 mJ/cm²) is nearly 5 times higher than commercial SESAM. The devices applied to generate femtosecond pulses exhibit exciting nonlinear optical effects, which enable the mode-locked fiber laser to operate with a pulse duration of 195 fs and a signal-to-noise ratio of 81.73 dB. This discovery not only proves that the passive mode-locked laser-based high transmittance Bi₂Se₃ can obtain reliable pulse output, but also provides a new perspective for the selection of saturable absorption materials in the future.