Femtosecond Fiber Laser Based on BiSbTeSe₂ Quaternary Material Saturable Absorber

Topological insulator materials, including Bi₂Te₃, Sb₂Te₃, Sb₂Te₃, and Bi₂Se₃, have attracted some attention due to their narrow band gaps, high carrier mobility, wide spectral absorption ranges and other characteristics. We report a new multi-compound topological insulator material BiSbTeSe₂ that, compared with the traditional topological insulator composed of two elements, can integrate the physical advantages of each element, helpful to build an experimental platform with rich physical properties. The nonlinear optical characteristics of the quaternary material BiSbTeSe₂ is obtained in the erbium-doped fiber laser. Using the BiSbTeSe₂ as a saturable absorber material, the passive Q-switched and mode-locked fiber lasers are achieved. The pulse duration and signal-to-noise ratio (SNR) of the Q-switched fiber laser are 854 ns and 70 dB, respectively. Meanwhile, the pulse duration and SNR of the mode-locked fiber laser are 259 fs and 87.75 dB, respectively. This work proves that the BiSbTeSe₂ has a considerable application prospect as a saturable absorber in fiber lasers, and provides a new reference for selection of high-performance saturable absorber materials.