光导板中新型衍射元件的数值模拟研究

基于严格耦合波理论,数值计算了一种在闪耀斜面镀膜的亚波长光栅结构,并首次提出将该光栅应用于光导板的设计中,使光导板衍射的RGB光束无需经过滤色片,直接透射相应的像素点。在数值计算中,设定入射光为TE偏振态、入射角为60°、波长为RGB三基色。光栅以有机玻璃为基底,二氧化钛为膜层,并随波长改变周期、闪耀角等参数。计算结果表明,该光栅的一级衍射光可垂直于表面出射,一级衍射效率随膜厚渐变,最高达37%,其余非零级次的衍射效率低于2%。将该特性的光栅应用于新型光导板的数值建模中,并对光栅的制作进行了工艺容差分析,计算得归一化能量的标准差小于1%,总衍射效率接近80%。

Numerical simulation of the new type grating used in LGP

Numerical study is made on a coated blazed grating based on rigorous coupled wave analysis (RCWA) and as far as known, for the first time the novel grating is used in the design of new type LGP, which can diffract the RGB light directly into the pixels without filter. The incident light is TE-mode with wavelengths of RGB and incident angle of 60°. The grating is composed of plexiglas with the coating made of Titanium dioxide; its cycle and thickness of the saw tooth are changed with the wavelengths. The result shows that the 1st order diffraction is perpendicular to the surface and its efficiency changes with the coating thickness with the peak of 37 % while the other high-orders’ are below 2 %. By applying the grating in the design of new type LGP and making tolerance analysis, the standard deviation of normalized energy is less than 1 % and the total efficiency is about 80 %.