Wavelength adjustability of PM-Yb-doped fiber laser based on FBGs for high power SHG generation

We focused on frequency conversion of simple and compact CW PM-Yb-doped fiber laser based on FBGs with wavelength adjustable function. By using the temperature dependency of FBG's center wavelength, it is possible to adjust the oscillation wavelength by controlling both FBG temperatures. We tested 6 mu m core based FBGs with at the center wavelength of 1040 nm, 1064 nm and 1090 nm. We found that it is possible to tune approximately 500 pm by controlling FBG temperatures between 15 and 85 degree-C. The tunability of wavelength was is around 6.0 similar to 8.5 pm/degree-C. It was possible to achieve 10 W of output for each wavelength. In addition, we applied this configuration to 10 mu m core fiber at center wavelength of 1064 nm. It was obtained wavelength adjustability of 8.3 pm/degree-C with output of over 35 W. Its linewidth is narrower than 50 pm and suitable for frequency conversion. The tuning range was similar to the 6 mu m core fiber case and slight difference and variations might be related to wavelength, refractive index distribution, thermal expansion coefficient, and fixation condition of FBGs. By using over 35 W fiber laser, it is possible to realize around 10 W of green-light SHG laser combined with high conversion efficiency QPM devices such as PP-Mg: SLTs with wavelength tunable function.