2.5D Low Refractive Index Designer Color Router for High-Transmission Image Sensor

The invention of colorful imaging devices is to help human being better collect the environment information and store it. Based on the three primary color theory, the three channel Bayer type color filters and the complementary metal-oxide semiconductor (CMOS) combination is the most used basic module in the colorful imaging devices. While the intrinsic filtering mechanism has faced the low-level energy utilization efficiency. To minimize the energy loss, color router is proposed as a new mechanism since it can redirect different wavelengths light in the near field. Recent efforts with high-refractive-index (HRI) metasurfaces to design the color router (CR) have proved the ability to greatly improve the efficiency. While low-refractive-index (LRI) materials with advantages of high transparency, cost-effectiveness and mass production manufacturability is still unexplored to be applied in realizing high-resolution, high efficiency color router. Here, we propose two types of high-efficiency pixel-size color routers with LRI material fabricated by two-photon polymerization lithography, which present peak collection efficiencies around 60% for red, green and blue light. They achieve a desired average energy utilization efficiency of around 97% and 85% separately across the visible band, corresponding to 3.5 and 3.3 times over the Bayer filter. Colorful imaging experiment is conducted together with the monochromatic camera and is compared with the commercial imaging devices which further proved our design and desired CR performance in the low light environment.