Ultrafast Thulium-Doped Fiber Laser Mode Locked by Monolayer WSe2

We report the usage of chemical vapor deposition-grown monolayer WSe
₂
as a saturable absorber (SA) for a mode-locked thulium-doped fiber laser. The monolayer WSe
₂
was transferred onto a microfiber and then incorporated into a typical all-fiber-integrated ring cavity configuration. Stable soliton pulses emitting at 1863.96 nm were obtained with pulse duration of 1.16 ps, repetition rate of 11.36 MHz, and an average power of 32.5 mW. This is, to the best of our knowledge, the first demonstration of WSe
₂
-based SA in fiber lasers at 2 μm regime.