2 µm sub-GHz harmonic mode-locked soliton generation based on a Bi<sub>2</sub>S<sub>3</sub> saturable absorber
Xiaohui Ma, Ziqi Zheng, Shanshan Ye, Yangyang Wang, Wu Chen, Shaoqing Liu, Liang Tong, Wenwen Dai, Yong Zhou, Wei Zhang, Wentan Fang, Xiaolin Chen, Song Huang, Meisong Liao, Weiqing Gao
Abstract
Saturable absorber (SA) based harmonic mode-locking (HML) techniques at 2 µm waveband are much less reported than those at 1.5 µm waveband, the maximum repetition rate of the harmonic pulse generated by such techniques at 2 µm waveband is also much lower than those generated at 1.5 µm waveband. In this paper, the 39th harmonic with the repetition rate of 908.6 MHz is realized in a Bi 2 S 3 -based thulium-doped fiber laser. The fundamental mode-locked pulse has a central wavelength of 1954.2 nm and a 3-dB bandwidth of 5.1 nm. The repetition rate is 23.27 MHz and the pulse width is 902 fs. The characteristics of the material and harmonic mode-locked pulse are investigated. To the best of our knowledge, this is the highest and the closest resonance frequency to GHz among the reported SA-based harmonic mode-locked fiber lasers operating at 2 µm waveband.