嵌入式镀膜光栅的数值模拟研究

嵌入式镀膜光栅是将平行四边形的介质膜层,以亚波长量级的周期嵌入波导中.针对该光栅在不同偏振态、不同角度入射下的各级衍射效率问题,本文基于严格耦合波分析理论,对该光栅进行建模与数值分析.结果表明,在TE模入射时,该光栅的一级衍射效率可随膜厚在0,37％]内变化,其余非零级次的衍射效率低于2％.衍射特性可以满足平视器成像的效率递增要求,同时可以减少能量的损失与杂散成像光线.当入射光束的角度在纵向45°,70°]、横向-15°,15°]内变化时,一级衍射效率的变化平稳,可以保持平视器不同视场的成像能量均匀.针对入射光偏振态、光栅材料、嵌入膜层倾角、光栅周期对衍射特性的影响,给出了相应的数值分析,可为波导全息平视器中衍射元件的制作提供理论指导.

Numerical Analysis of the Buried Parallelogramic Grating

The buried parallelogramic grating is to embed tilt dielectric film in the waveguide with sub-wavelength cycles. Based on rigorous coupled-wave analysis, the grating is modeled and numerically analyzed. The diffraction efficiency under different polarization states and incident angels is calculated. The result shows that with the TE-mode incidence, the 1st order diffraction efficiency varies between ［0, 37%］ with the film thickness and stays almost the same with the change of incident angles. The other non-zero orders′ efficiencies are below 2%. This feature could satisfy the increasing efficiency required in the head-up display. It could also reduce the energy loss and unwanted image rays. When the incident angle changes between ［45 °, 70 °］ in vertical and ［－15 °, 15 °］ in horizontal, the 1st order diffraction efficiency stays almost the same to maintain the uniform display in different view fields. The effect on the diffraction efficiency is also discussed with the change of polarization, inclination, cycle and materials. This article can provide theoretical guidance in the manufacture of the grating.