Saturable absorption may be induced at critical pumping power by nonlinear optical effects of nanomaterials, thereby making it possible to generate a high-power ultrafast laser. Recently, Bi4Br4 is theoretically predicted to be a member of topological insulators and is expected to be a promising candidate for saturable absorbers (SAs). We show here that Bi4Br4 features a large modulation depth of 42.3%. The Bi4Br4-based SA enables mode-locking operation at the near-infrared range, as demonstrated here by a 1.5 μm fiber laser with a signal-to-noise ratio (SNR) of 90 dB and a pulse duration of 172 fs. Moreover, the robustness of the Bi4Br4-based SA at relatively high power is of particular interest, which can be proved by a laser's stable operation state. The strong optical nonlinearity and robustness provided by Bi4Br4 may arouse a growing upsurge in the innovation of high-power ultrafast photonic devices and further development of photon applications.
Bi4Br4-based saturable absorber with robustness at high power for ultrafast photonic device
Wenjun Liu, Xiaolu Xiong, Mengli Liu, XiaoWei Xing, Hailong Chen, Han Ye, Junfeng Han, Zhiyi Wei; Bi4Br4-based saturable absorber with robustness at high power for ultrafast photonic device. Appl. Phys. Lett. 31 January 2022; 120 (5): 053108. https://doi.org/10.1063/5.0077148
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