Monolithic Tm-Doped Fiber Laser at 1951 nm With Deep-UV Femtosecond-Induced FBG Pair

We report on a monolithic Tm-doped fiber laser emitting in the region ${\sim}{\rm 2}~\mu{\rm m}$ . A pair of fiber Bragg gratings (FBGs) was written into the Tm-doped fiber using a two-beam interferometry and a deep ultraviolet (DUV) femtosecond laser source at 266 nm. Such a monolithic setup allows a simple setup of the laser made of a single fiber only. This configuration also offers greater reliability because fusion splices inside the resonator cavity could eventually generate failure in the laser cavity. To the best of our knowledge, this is the first rare-earth-doped fiber laser with an FBG pair written by DUV femtosecond laser radiation. Laser characteristics are presented as well as compared with the fiber laser with external FBGs conventionally spliced to the Tm-doped fiber. Dependence of the laser wavelength on the pump power is investigated in detail.