基于严格耦合波理论的新型耦合光栅分析

Numerical Analysis of a Novel Coupling Grating Based on RCWA

针对波导全息平视器中一种新型的耦合光栅结构,基于严格耦合波理论数值分析了其衍射特性,同时对光栅的工艺容差进行了分析,计算了膜厚、槽深、周期与入射波长对耦合效率的影响.该光栅以波导板中内嵌的闪耀光栅锯齿面作基底,镀高折射率的膜层后,覆盖锯齿状的金属膜层.计算结果表明:对于波长532,nm的TE偏振光,空气中0°入射的一级衍射效率可大于90%;当空气中入射光的纵向角在[-8°,12°]、横向角在[-15°,15°]内变化时,一级衍射效率可大于82%且保持平稳.该光栅可在波导全息平视器中,对大视场成像光束进行均匀、高效的耦合.

A novel coupling grating could play an important part in the waveguide holographic helmet mounted dis-play,but to our knowledge few documents reveal its diffraction features in detail. Based on rigorous coupled wave analysis,the diffraction features are numerically analyzed. Tolerance analyses are also made of film thickness, groove depth,cycles and incident wavelength. The grating base is like the blazing grating etched in the waveguide. On the tilt surface,the film with high refractive index is first coated and then the metal is coated on the film in suc-cession. The results show that for the TE-polarized incident light of 532,nm,the 1st order diffraction efficiency is larger than 90%with perpendicular incidence. It could remain stable with the incident angle from the air changing be-tween [-8＆#176;,12＆#176;] vertically and [-15＆#176;,15＆#176;] horizontally. The 1st diffraction efficiency could be larger than 82%and keep stable. The proposed coupling grating could couple the image rays from large view fields into the display device with high efficiency and uniformity.