谱合成是获得高功率激光输出的有效方法。反射布拉格光栅衍射旁瓣是影响谱合成效率的主要因素。建立了sinc切趾布拉格光栅谱合成理论模型，采用传输矩阵法，分析了光栅参数对切趾光栅衍射特性的影响，以及入射光束光谱宽度和发散角对谱合成效率的影响。计算结果表明：sinc切趾布拉格光栅可有效抑制衍射旁瓣的影响，其一级衍射旁瓣和二级衍射旁瓣的峰值分别由62%和36%下降为0.57%和0.12%。通过优化光栅参数，利用sinc切趾布拉格光栅可实现窄光谱间距、高谱合成效率的多光束谱合成。切趾后，在10 nm的带宽内，参与谱合成光束的数目由7束增加为25束。对于波长为1 064 nm和1 064.4 nm的两束光谱合成，当入射光束光谱宽度小于0.15 nm，且发散角小于0.8 mrad时，谱合成效率达90%以上。

Spectral beam combining technology is an effective approach to obtain high-power laser output. The side-lobe in diffraction efficiency of reflection Bragg grating is the main factor which limits the efficiency of spectral beam combining. In this paper, the theoretical model of spectral beam combining system based on the sinc-apodized Bragg grating is proposed. The diffraction characteristic of the sinc-apodized grating is analyzed by the chain-matrix approach, and the effects of spectral width and beam divergence on combining efficiency are considered. Numerical analysis show that the side-lobe in diffraction efficiency is suppressed well after using the sinc-apodized grating, the peaks of the first side-lobe and second side-lobe are reduced from 62% and 36% to 0.57% and 0.12%, respectively. The narrow spectral separation and high efficiency of spectral combining can be achieved after optimizing the sinc-apodized grating’s parameters. The number of wavelength channel is increased from 7 to 25 in a total 10 nm bandwidth after using sinc-apodized grating, and the combining efficiency of two beams can be more than 90% theoretically when the spectral width is less than 0.15 nm and the angular divergence is less than 0.8 mrad at wavelength of 1 064 nm and 1 064.4 nm.