High brightness laser diode through open-loop spectral beam combining based on a VBG (volume Bragg grating) device

We have carried out what we believe to be a novel design for wavelength stabilization and spectral beam combining, focusing on increasing the brightness of fiber coupled laser diode (LD) based on a VBG (volume Bragg grating) device. The small size VBGs which can be called miniature VBGs with diffraction angle of 0.4 degrees are used to lock spectrum, and the large-scale size VBG which can be called primary combining VBG with diffraction angle of 6 degrees is employed to combine with two sub-beams. The fiber coupled LD module is used as sub-beam whose beam parameters such as point error, pupil deviation, center wavelength and spectral width can be conveniently controlled by fiber adjustment instead of each single chip compared to direct spatial light output. The locked spectral width of sub-beam is less than 0.3 nm (FWHM, full width at half maximum), the power after beam combining is more than 800W, the BPP (beam product parameter) is less than 15 mm·mrad containing 95% energy, which can be coupled into fiber of core diameter with 200 µm, NA (numerical aperture) less than 0.15.