复用体布拉格光栅具有良好的波矢选择性以及可控的衍射效率。根据Kogelnik耦合波理论，分析复用体布拉格光栅作为谐波分离以及光束取样元件的可行性。结果表明，采用复用两片反射型以及单片透射型体布拉格光栅的结构，使得两片反射型体布拉格光栅对混有三个倍频成分的主光束中的基频、二倍频光束(1053 nm和527 nm)高效率衍射（色分离度分别为0.2%和0.3%），而对三倍频光束(351 nm)高效率透射（接近于100%），以达到谐波分离的目的；而透射型体布拉格光栅对三倍频光束低效率衍射(等于0.98%)，且衍射光束的空域时域光强分布与三倍频光束基本一致，以达到光束取样的目的。因此复用体布拉格光栅可同时实现谐波分离以及光束取样的功能，这给传统谐波分离以及光束取样光栅提供了一种备选方案。

Superposed volume Bragg gratings (SVBG) has the characteristics of excellent wave vector selectivity and adjustable diffraction efficiency. Based on Kogelnik′s coupled wave theory, the potential applications of SVBG for harmonic-wave separation and beam sampling are analyzed. The results show that the SVBG is made up of two pieces of reflecting volume Bragg grating (VBG) and one piece of transmitting VBG. The two pieces of reflecting VBG can highly diffract fundamental frequency and second harmonic beams (harmonic-wave separation ratios are 0.2% and 0.3% respectively), while do little effects on the third harmonic beam (transmittance is up to nearly 100%) in order to make the harmonic-wave separation. The transmitting VBG has low diffraction efficiency for third harmonic beam (only 0.98%). The spatial and temporal intensity distributions of the diffractive beam are similar to those of the third harmonic beam, so the harmonic-wave separation and beam sampling can be realized simultaneously based on the SVBG. The SVBG is a good potential substitution for the traditional grating for the harmonic-wave separation and beam sampling.