Wavelength stabilized laser module for highpower fiber laser pumping
The paper presents the results of development of wavelength stabilized laser modules where wavelength stabilization is achieved due to volume Bragg gratings with a 976 nm operating wavelength. The module was designed to spatially combine the light from six high-power laser diodes with its subsequent coupling into a silica fiber with a core diameter of 105 μm and a numerical aperture of 0.15. Stabilization scheme was realized, where volume Bragg
gratings were placed behind the lenses used for light collimation along the slow axis. Laser diode performance was studied for volume Bragg gratings with different reflectivity factors. The measurement results were used to determine optimum reflectivity of volume Bragg gratings; the spectral and power characteristics of the manufactured laser module were measured. The volume Bragg gratings allowed for significant, down to 0.5 nm, narrowing of the laser module spectrum width and wavelength stabilization over the entire range of operating currents. In continuous mode, the manufactured laser module power reached 43.6 W at a pumping current of 10 A and a thermal stabilization temperature of 25°C.