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 μm 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 6.0~8.5 pm/degree-C. It was possible to achieve 10 W of output for each wavelength. In addition, we applied this configuration to 10 μm 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 μm 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.
We developed the dual line fiber laser module based on FBG combination. The proposed configuration has several advantages such as compact, simple, and inexpensive. The laser was composed pump LD (40W), two HR FBGs for 1053 nm and 1058 nm, Yb-doped fiber, two OC FBGs for 1053 nm and 1058 nm, and delivery fiber. All single mode fibers were polarization maintained with approximately 6 micron core. All FBGs were mounted on holders with TECs and their temperatures were controlled independently. The center wavelengths of HR and OC FBGs were temperature dependent and their shifts are approximately 7 nm/degree-C for all integrated FBG. By adjusting the temperature, it is possible to realize the resonant condition for only 1053 nm or only for 1058 nm. Based on this configuration, we demonstrated dual line CW fiber laser module. This module was compact with the size of 200 mm X 150 mm X 23 mm. By adjusting the FBG temperatures, we obtained the output power of more than 10 W at 1053 nm and 1058 nm with linear polarization.
We focused on wavelength conversion of simple and compact CW Yb-Doped fiber laser based on FBGs with wavelength adjustable function. By controlling temperatures of FBGs in fiber laser, it was possible to tune oscillated wavelength from 1064.101 nm to 1064.414 nm with more than 20 W in CW operation mode. Based on this fundamental light, frequency converted light (SHG and THG) were generated by utilizing two PP:Mg-SLT devises. We obtained more than 3 W of SHG light with tuning range of 150 pm and more than 35 mW of THG with tuning range of 100 pm. By selecting FBG grating and QPM grating properly, we can realize adjustable wavelength laser with the same scheme from 1040 nm to 1090 nm and their SHG/THG. With this combination of FBG based fiber laser and QPM devices, it is possible to tune the wavelength just by temperature tuning without any changes of beam shape and beam pointing.