Research On External Cavity Spectral Beam Combining Of Fiber Lasers

Spectral beam combination of fiber lasers is a effective way to break through the limitations of single-mode fiber laser.All the beams are arranged in the same propagation direction by the dispersion of the grating,because of their different incident angles and different wavelengths.The coincidence of all the beams from the emitters is realized in the space,achieving the spectral beam combining.The output power of the SBC is the sum of the power of the lasers participating the SBC,while preserving the beam quality of the individual fiber lasers.There is no necessity for a complex phasing control system in the SBC,which makes SBC a practical way for fiber laser power scaling.In this paper,a theoretical analysis and experimental study on spectral beam combining are discussed.The main completed work is as follows:The evaluation method of laser beam is given.The principle of spectral beam combining is described.The effect of related parameters on spectral beam combining is analyzed theoretically.The key parameters of SBC and the measurement methods of these parameters are given.The HR FBG and Yb-fiber damage problem is analyzed while the protection solutions for these problems are given.Coating a film of 1%reflectivity on the end facet of the fiber laser or reducing the reflectivity of OC FBG can solve this problem.A novel spectral beam combining configuration is demonstrated.In this novel SBC configuration,off-axis aberration and feedback insufficiency are eliminated by replacing one single transform lens with several individual transform lenses.The coupling efficiency of this novel SBC configuration is verified via ZEMAX stimulation.The spectral beam combining of three fiber lasers is achieved.This system consists of a1060nm laser,a 1070nm laser and a 1080nm laser.M~2 value of 1.388 in SBC direction is obtained,while M~2 value in the other direction is 1.305.The output power of the SBC system is 86.0W with a combining efficiency of 91.8%.Thermal stimulation analysis on the SBC system has been carried out,and the stability of the dispersion element is verified,paving the way toward kilowatts external cavity SBC.