Bidirectional mode-locked erbium-doped fiber laser based on an all-fiber gold nanofilm saturable absorber

• Published in: Optics express 2024-01, Vol.32 (2), p.1851-1863
• Main Authors: Lv, Changjian, Meng, Fanchao, Yan, Qi, Zhang, Tianqi, Tian, Yiwei, Jia, Zhixu, Dong, Wei, Qin, Weiping, Qin, Guanshi
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.514835

We demonstrate a bidirectional mode-locked erbium-doped fiber laser by incorporating gold nanofilm as a saturable absorber (SA). The gold nanofilm SA has the advantages of high stability and high optical damage threshold. Besides, the SA exhibits a large modulation depth of 26% and a low saturation intensity of 1.22 MW/cm at 1.56 μm wavelength band, facilitating the mode-locking of bidirectional propagating solitons within a single laser cavity. Bidirectional mode-locked solitons are achieved, with the clockwise pulse centered at 1568.35 nm and the counter-clockwise one at 1568.6 nm, resulting in a slight repetition rate difference of 19 Hz. Moreover, numerical simulations are performed to reveal the counter-propagating dynamics of the two solitons, showing good agreement with the experimental results. The asymmetric cavity configuration gives rise to distinct buildup and evolution dynamics of the two counter-propagating pulses. These findings highlight the advantage of the gold nanofilm SA in constructing bidirectional mode-locked fiber lasers and provide insights for understanding the bidirectional pulse propagation dynamics.