All-dielectric double split ring metasurface for structural colour generation

The metasurfaces are attractive artificially structured materials in the Nano-photonics domain. The metal-dielectric metasurfaces are promising but experience high losses in optical wavelengths. This drawback is overcome by the use of all-dielectric metasurfaces (ADMS). The specifically designed ADMS based on double split silicon (Si) ring can produce the sharp Fano-resonance characterised by the asymmetric line shape. The Mie resonance in high index Si dielectric produces high Q-factor resonance. Such types of ADMS based Fano-resonances are capable of providing refractive index sensors with high figure of merit and optical modulators with broadband tunability. In this work, we show that the above ADMS producing Fano-resonance can be utilized to achieve structural colours where Fano-resonance with small linewidth and sharp peaks generate highly pure and saturate colour gamut. By scaling the feature size of metasurface, we are able to produce Fano resonance in reflectance profile with peak position at 360 nm, 541 nm and 720 nm, which corresponds to colours in visible spectrum, respectively. The linewidth of Fano-resonance for structural colour is in range of 8 to 17 nm. Such structures can be used in pixels of next-generation reflective colour displays.