Multiresonant silicon-based nanopillar metasurface for narrowband RGB color filter

The performance of conventional silicon (Si) -based metasurfaces is limited by intrinsic losses and low quality factors (Q). Here, we numerically investigate a silicon-based nanopillar RGB metasurface that exploits symmetry-tuned high-Q resonances (Q-BIC-like) enabled by intentional in-plane symmetry breaking. To mitigate substrate-induced non-radiative losses, a thin silicon nitride (Si₃N₄) interlayer is introduced between the metasurface and the Si substrate, providing improved refractive-index matching and reduced energy leakage into the substrate. This combined design leads to enhanced electromagnetic field confinement and narrower spectral responses. As a result, the reflection peak full width at half maximum (FWHM) is reduced from 103 nm and 77 nm to 51 nm and 48 nm for the red and green channels, respectively, accompanied by a 1.4× enhancement in local field intensity for the red channel. Furthermore, macro-pixel configurations based on Bayer-like arrangements demonstrate low spectral crosstalk and high color purity. These results demonstrate a practical metasurface design strategy for narrowband RGB color filtering in integrated micro-display and imaging applications.