Direct femtosecond laser inscription of Bragg gratings in Ho<sup>3+</sup>/Pr<sup>3+</sup> co-doped AlF<sub>3</sub>-based glass fibers for a 2.86 µm laser
Niannian Xu, Zhiyong Yang, Jiquan Zhang, Nian Lv, Mo Liu, Ruoning Wang, Zhenrui Li, Shijie Jia, Gilberto Brambilla, Shunbin Wang, Pengfei Wang
Abstract
In this Letter, we report the fabrication of fiber Bragg gratings (FBGs) in home-made Ho 3+ /Pr 3+ co-doped single-cladding fluoroaluminate (AlF 3 ) glass fibers and its application in watt-level lasing at the mid-infrared (MIR) wavelength of 2.86 µm. The FBGs were inscribed using an 800 nm femtosecond (fs) laser direct-writing technique. The FBG properties were investigated for different pulse energies, inscription speeds, grating orders, and transversal lengths. A second-order FBG with a high reflectivity of 99% was obtained at one end of a 16.5-cm-long gain fiber. Under 1150 nm laser pumping, this fiber yielded a power exceeding 1 W at 2863.9 nm with an overall laser efficiency of 17.7%. The fiber laser showed a FWHM bandwidth of 0.46 nm and long-term spectral stability.