| High power fiber lasers in industrial applications, especially in the field of laserprocessing, laser cutting and marking is gradually occupied an increasingly importantposition. Due to the impact factors of the fiber dispersion effects, nonlinear effects andproduction costs, it’s difficult to obtain the higher power output, so the group-beamtechnology has been proposed, which is include spectral beam and coherent beam combiningtechnology.The basic principle of spectral beam combining technology is to use the dispersiveelement to combine the beam array. It doesn’t need to control the phase, amplitude andpolarization while maintaining good beam quality. It’s a important technology to achievehigh power of fiber laser systems.In this thesis, we researched the spectral beam combining technology based on volumegrating and designed optimal high-power laser beam combination. When the beam order theBragg condition of volume grating, it has high diffraction efficiency. If one beam violatedthe Bragg condition, it will cause the diffraction efficiency decreased. Based on this principlewe can be realized the spectral beam combining with different wavelengths.According to Kognelnk’s coupled-wave theory of the volume grating, we analyzed thebasic theory of reflection volume grating, transmission volume grating and volume gratingcharacteristics. We also created two types of the volume grating spectral beam parameteroptimization model to achieve high efficiency spectral beam combining. The combiningefficiency is up to95%with Gaussian beam. Based on transmission volume grating spectralbeam model of the two-way and three-way, we expansion multi-channel spectral beamcombination model and discussed the impact of loss and crosstalk to the efficiency of beamcombination.Based on the coupled wave theory we proposed the parameters optimization model ofthe volume grating. There are constructive suggestions for the efficient production of volumegrating and high-power laser beam combining technology. |
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