A multiple soliton state erbium-doped fiber laser based on SnBi 2 Te 4 saturable absorber

Abstract With the growing research on topological insulators (TIs) in recent years, a variety of novel TIs with excellent nonlinear optical properties have been synthesized—such as SnBi 2 Te 4 . Its strong absorption in the near-infrared region makes it a promising candidate as a saturable absorber (SA) for utilize in passively mode-locked fiber lasers. In this experiment, SnBi 2 Te 4 was thoroughly characterized, and a nanosheet solution was prepared via liquid-phase exfoliation (LPE). The nanosheets were then deposited onto the tapered region of a tapered optical fiber via the optical deposition method (ODMs) to fabricate the saturable absorber, exhibiting a modulation depth of 6.058% and a saturation intensity of 15.32 MW cm −2 . The fiber laser incorporating the SnBi 2 Te 4 SA was able to generate conventional soliton pulses with a central wavelength of 1532.13 nm, with a signal-to-noise ratio of 60.18 dB. By increasing the pump power, 59th-order harmonic mode-locking was successfully achieved. Furthermore, by adjusting the polarization controller (PC), multi-pulse outputs ranging from the 2nd to the 9th order could be flexibly generated, with smooth switching between different pulse states. These results demonstrate that SnBi 2 Te 4 possesses excellent pulse modulation capabilities and holds significant potential as a promising ultrafast laser modulator for future research applications.