Performance of Bi-Directional Mode-Locked Fiber Laser at 2 μm

Bidirectional mode-locking pulse laser has attracted great attentions because of its simplicity and compactness for free-running dual-comb spectroscopy. In this paper, we developed an all-polarization- maintaining, bi-directional Tm-doped fiber laser at 2 μm with a single-wall carbon nanotube (SWNT) presented as saturable absorber mode-locking mechanism. By manipulating the polarization controller, changing the pump power and shortening the cavity length, we successfully obtain bidirectional mode-locking operations at different repetition frequencies, namely 35 MHz and 122 MHz. Besides, the repetition rate difference between the clockwise and counterclockwise pulse trains is adaptable, varying from 764 Hz to 1.01 KHz at 35 MHz and 540 Hz to 1.8 KHz at 122 MHz.