Effects of roughness and resonant-mode engineering in all-dielectric metasurfaces

The development of all-dielectric metasurfaces vigorously prompts the applications of optical metasurfaces for the visible and near-IR light range. Compared to IR or longer wavelength light, visible and near-IR light have shorter wavelengths. As a result, surface roughness and imperfections of all-dielectric metasurfaces have larger scattering or absorption of visible and near-IR light, thereby directly affecting the performance of an all-dielectric metasurface. In this article, a volume-current method is adopted to study the effect of metasurface roughness. Numerical calculations based on the finite difference time domain (FDTD) method are also used to study the relationship between the effects of metasurface roughness and the optical resonant modes. Numerical predictions based on our theoretical studies fit the experimental data well. Further, the effect of different roughness levels on the all-dielectric metasurface performance is predicted. More importantly, a method utilizing resonant-mode engineering to enhance the metasurface performance (e.g. incident angle insensitivity) is also proposed and demonstrated. This work deepens our understanding of the working mechanism of all-dielectric metasurfaces and paves the way for their use in a broad spectrum of applications.