多重结构对体全息光栅衍射角带宽的拓展

Diffraction Angular Bandwidth Broadening of Volume Holographic Grating by Multiplex Structures

以Kogelnik耦合波理论为基础,从理论上分析了反射体全息光栅衍射效率的影响因素,提出了采用多光栅重叠衍射拓展体全息光栅角带宽的方法。针对衍射均匀性的要求,分析了多重光栅重叠衍射的物理过程,给出了相邻光栅拼接时的布拉格角偏移量,得到了多重光栅衍射角带宽随光栅重数和折射率调制度的变化关系。理论计算结果表明,多重光栅衍射角带宽与多重光栅数量和光栅折射率调制度均呈现出线性增加的关系。在合适的折射率调制度下,通过增加光栅数量可显著增加衍射角带宽。

Based on Kogelnik＇s coupled-wave theory, diffraction efficiency of reflection volume holographic grating is analyzed for several parameters. We propose a method to broaden the diffraction angular bandwidth by superposing multiplex volume holographic gratings, each of which is oriented properly. Permised on the requirement of uniform diffraction, the diffraction process in multiplex volume gratings is analyzed to acquire the offset of Bragg angle between adjacent gratings, and the uniform-diffraction bandwidth versus multiple numbers and refractive index modulation are finally obtained. Numerical results show that diffraction angular bandwidth of multiplex volume holographic gratings increases linearly with the number of multiplex gratings and refractive index modulation depth. The angular bandwidth can be broadened markedly via increasing the number of superposed gratings with appropriate refractive index modulation depth.