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提出了一种基于级联体光栅(VBG)的谱组束方案,组束阵元数可随级联体光栅的数目倍增。给出了一个双光栅级联谱组束系统实例,将组束阵元按波长分为两组,利用具有相应波长选择性的体光栅分别对它们进行组束,由于两个级联体光栅的角度选择性互不重叠,所有光束经第二个体光栅后都沿其布拉格(Bragg)角方向出射,实现近场和远场的功率叠加。为保证各光束传播方向的一致性,采用严格耦合波理论推导出了准确计算光束入射角的解析式。数值计算结果表明各光束的平均衍射效率优于80%,在入射角偏离理论值不超过±5′(≈2.424×10-5rad)的条件下组束光中所有光束的传播方向偏差小于4×10-7rad。
A spectral beam scheme based on cascade volume grating (VBG) is proposed. The number of group beam array elements can be doubled with the number of cascaded grating. An example of a two-grating cascade grouping beam system is given. The grouping array elements are divided into two groups according to the wavelength. The two groups are respectively bundled by the volume grating with the corresponding wavelength selectivity. The angular selectivity does not overlap each other, and all the light beams exit through the Bragg angle after passing through the second individual grating to achieve the power superposition in the near field and the far field. In order to ensure the consistency of the propagation directions of the beams, the analytic formula for accurately calculating the incident angle of the beam is deduced by using the strictly coupled wave theory. The numerical results show that the average diffraction efficiency of each beam is better than 80%. The deviation of the propagation direction of all the beams in the beam is less than 4 × when the incident angle deviates from the theoretical value by no more than ± 5 ’(≈2.424 × 10-5 rad) 10-7rad.