单层与双层谐衍射元件的衍射效率对比分析

Comparison analysis on the diffractive efficiency of single-layer and double-layer harmonic diffractive optical element

由于单层谐衍射元件只在谐振波长处能精确闪耀,随着波长偏离谐振波长,衍射效率迅速下降,导致宽波段成像质量变差。为了将谐衍射元件的应用拓展到宽波段,重点对可等效为普通单层衍射元件的双层谐衍射元件的衍射效率进行了详细的分析。理论分析得出:此种双层谐衍射元件的衍射效率在整个设计波段明显高于单层谐衍射元件的衍射效率,而且在整个设计波段的分布基本平衡。进一步以可见光波段的常用材料ZF7和QK3构成的单层和双层谐衍射元件为例,对衍射效率进行了Matlab模拟。结果表明:理论定性分析与模拟的定量结果基本一致。这为双层谐衍射元件应用于宽波段成像领域提供了有力的理论依据。

Single-layer harmonic diffractive optical element （HDOE） can only blaze at the harmonic wavelength. The diffractive efficiency will rapidly drop, as the wavelength deviates with harmonic wavelength, which will lead to bad imaging quality over wide wave band. In order to extend the application of HDOE to wide wave band, the diffractive efficiency of double-layer HDOE which was equivalent to common single-layer diffractive optical element （DOE） was analyzed. The result shows that the diffractive efficiency of the double-layer HDOE is evidently higher than that of single-layer HDOE, and the spectral distribution of the diffractive efficiency basically keeps balance over the whole design wave band. The diffractive efficiency of single-layer and double-layer HDOE made of ZF7 or QK3 was simulated by Matlab software respectively, which was used widely in the visible light wave band. The results show that the numerical simulation quantitative analysis is consistent with the theoretic qualitative analysis . The above method and results will provide powerful theoretical foundation for double-layer HDOE application in the imaging field over wide wave band.