Fig. 1. Comparison between traditional Bayer color routers and color routers achieved using different optical materials

Fig. 2. Color routers based on metallic micro-nano structures. (a) Bullseye metallic ring lens structure^[61]; (b) metallic film nanopore resonant waveguide structure^[29]; (c) heterometallic nanoantenna resonant structure^[62]; (d) metallic grating integrated with dielectric waveguide structure^[63]

Fig. 3. Color routers based on multi-level grating structure with low-refractive-index materials. Scanning electron microscopy (SEM) image of the multi-level grating structure (a) and its beam-splitting results (b)^[98]; SEM image of the multi-level strip grating structure (c) and its beam-splitting results at 2 mm and 1 mm distances (d)^[99]

Fig. 4. Color routers based on high-refractive-index dielectrics. (a) GaN metalens color router based on geometric phase^[46]; (b) resonant color router using SiN microplate scattering^[51]; SiN (c‒e) and TiO₂ (f) resonant color routers designed via resonant phase^[114-117]; (g) SiN color router designed via propagation phase^[48]

Fig. 5. 3D structural color routers. (a) 3D color router based on a hybrid SiO₂/TiO₂ structure, minimum feature size: 10 nm^[120]; (b) 3D color router based on a hybrid SiO₂/SiN structure, minimum feature size: 10 nm^[7]; (c) 3D color router based on a hybrid SiO₂/TiO₂ structure, minimum feature size: 60 nm^[52]; (d) 3D color router using low-refractive-index 3D-printed photoresist structure^[52]; (e) experimentally demonstrated mid-infrared band 3D color router based on 3D-printed low-refractive-index photoresist^[123]

Fig. 6. Comparison of the nanophotonics-based color routers and the future development