Effect of rounded angle on the sharp corners of meta-atoms in dielectric metasurface

Optical metasurfaces have attracted much attention in recent years, due to their versatile capabilities to manipulate electromagnetic waves within subwavelength scale. Dielectric metasurface holograms can significantly improve resolution, efficiency, view angle and suppression of the high order diffraction compared to traditional devices. The ability to completely control the optical properties of light using metasurface is sensitive to the geometric parameters of the nanostructures. However, current metasurface fabrication methods often result in unavoidable structural deformations. Here we introduce the rounded angles (fillets) to the sharp corners of the meta-atoms, such as rectangular pillars and isosceles triangular pillars, in dielectric metasurface and numerically study the effect of these fillets under different symmetric conditions. We find that with specific radii of the fillets, bound states in continuum (BICs) appear, making the structure act as an absorber. Apart from these BICs, fillets that do not break the original symmetry of the meta-atoms have almost no effect on the manipulation of incident light by the metasurface. However, for fillets that break the original symmetry of the meta-atoms, the amplitude and phase manipulation by metasurface may be distorted.