面向增强现实的多模干涉型RGB波导合波器的对比研究

A Comparative Study of Multi-mode Interference RGB Waveguide Combiner for Augmented Reality (AR)

RGB合波器作为激光扫描显示系统的关键性核心部件,其微小型化和高传输效率是应用于增强现实的必然要求。针对氮化硅、氮化镓、SU8三种可见光波段高透过率材料,对比研究了其波导的折射率差、色散曲线、单模条件,以及所构成的多模干涉型RGB波导合波器的尺寸、传输效率、光场分布。研究结果表明,氮化硅器件的各项性能介于氮化镓与SU8器件之间;氮化镓器件具有最大的芯层与包层折射率差,最小的单模截止尺寸,最短的器件长度(2 000μm);SU8器件具有最小的芯层与包层折射率差,最大的单模截止尺寸,但器件长度大于氮化镓,为3 600μm。此外,氮化硅、氮化镓、SU8三种器件的RGB平均传输率分别为78%,55%和91%,可见SU8器件占有明显优势。未来,经过进一步优化设计的超紧凑氮化镓多模干涉型RGB波导合波器有望应用于激光扫描单片集成系统中,而具有良好柔性的SU8多模干涉型RGB波导合波器则在可形变系统中具有重要应用价值。这些器件为增强现实系统朝着微小型化和高传输效率的方向发展提供了技术基础。

As a key component of laser scanning display system,it is an inevitable requirement for RGB combiner to be of miniaturization and high transmission efficiency applied in augmented reality.Waveguides formed by three different materials with high transparency in visible light band,such as silicon nitride,gallium nitride and SU8,were comparatively studied in aspects of refractive index difference,dispersion curve and single mode condition,as well as dimension,transmission efficiency and optical field distribution of multi-mode interference RGB waveguide combiners based on the waveguides.The results show that the performances of silicon nitride devices are somewhere between those of gallium nitride devices and SU8 devices.Gallium nitride devices have the largest core-cladding refractive index difference,the smallest single-mode cut-off size,and the shortest device length(2 000 μm).SU8 devices have the smallest core-cladding refractive index difference,the largest single-mode cutoff size,but the larger device length(3 600 μm) than that of gallium nitride devices.In addition,the average RGB transmission rate of the silicon nitride,gallium nitride and SU8 devices are 78%,55% and 91%,respectively.The SU8 device dominates obviously.The optimized ultra-compact gallium nitride multi-mode interference RGB waveguide combiner is expected to be integrated to laser scanning monolithic systems,while SU8 multi-mode interference RGB waveguide combiner has great practical value in deformable systems due to its well flexibility.Those devices provide a solid technical foundation for the development of augmented reality systems towards microminiaturization and high transmission efficiency.