Narrow linewidth tunable CW thulium fiber lasers with VBG and GMRF stabilization

Eye-safe, high power tunable narrow linewidth lasers are important for various applications such as atmospheric propagation measurements. We have investigated two techniques of generating narrow linewidth thulium 2-μm fiber lasers, utilizing a reflective volume Bragg grating (VBG), and a guided mode resonance filter (GMRF) as a cavity end mirror. A stable narrow linewidth (50 pm), tunable (from 2004 nm to 2054 nm) thulium doped fiber laser using a reflective VBGg was demonstrated. A CW power of 17 W was achieved. Using a GMRF as an end mirror we showed a narrow linewidth (~30 pm) laser with an output power of 5.8W, and at a slope efficiency of 44%.