2 μm sub-GHz harmonic mode-locked soliton generation based on a Bi2S3 saturable absorber

Authors：Ma, Xiaohui; Zheng, Ziqi; Ye, Shanshan; Wang, Yangyang; Chen, Wu; Liu, Shaoqing; Tong, Liang; Dai, Wenwen; Zhou, Yong; Zhang, Wei; Fang, Wentan; Chen, Xiaolin; Huang, Song; Liao, Meisong; Gao, Weiqing^*

Source：Optics Express, 2022, 30(2): 2278-2287.

DOI：10.1364/OE.446876

• FIBER LASER
• LOCKING
• NANOSHEETS

Saturable absorber (SA) based harmonic mode-locking (HML) techniques at 2 mu m waveband are much less reported than those at 1.5 mu m waveband, the maximum repetition rate of the harmonic pulse generated by such techniques at 2 mu m waveband is also much lower than those generated at 1.5 mu m waveband. In this paper, the 39th harmonic with the repetition rate of 908.6 MHz is realized in a Bi2S3-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 mu m waveband.