We report the first-of-its-kind compact and robust coherent source operating in mid-IR based on Fe:ZnSe chalcogenide gain medium optically pumped by Er:ZBLAN fiber laser. In the research, we study the CW operation of cryogenically cooled laser based on Fe:ZnSe single crystals with different doping level grown from the vapor phase on a single-crystal seed by using the concurrent-doping technology. The maximal output power achieved is 2.1 W with 59% slope efficiency with respect to absorbed pump power, which is close to the Stokes shift limit. Measured Fe:ZnSe output spectra indicate a significant influence of re-absorption on generation wavelength. For high doping levels and output powers, spectrum shifts to the red wing, which makes possible continuous tuning from 4012 to 4198 nm. As well, tunability of the laser in a wide range of temperature is investigated.
We report the femtosecond laser inscription of fiber Bragg gratings (FBGs) in an Er-doped fluoride glass fiber used for lasing at a mid-infrared wavelength of 2.8 μm. FBG reflectivity and laser output power are observed with varying the index change of grating plane. We have tried to create high-index-contrast grating planes worked as Bragg reflector. The index change was estimated by fitting experimentally obtained reflectivity to its calculation. When using laser fluences of 25 and 40 J/cm<sup>2</sup>, the index change was found to be 0.7×10<sup>-3</sup> and 1.1×10<sup>-3</sup>, respectively. When using laser fluence of 25 J/cm<sup>2</sup>, FBG reflectivity increases up to 95% at the grating length of 4.0 mm. The case of using 40 J/cm<sup>2</sup> shows 97% at the grating length of 2.5 mm. These results are in agreement with the reflectivity calculation. The investigation of lasing evolution will contribute to more efficient fabrications of FBG and fiber laser system.