Design method for large-scale wide field-of-view monochromatic metalenses

Abstract

We propose a novel design method for wide field-of-view monochromatic metalenses. The proposed technique partitions the outer region of a metalens into supercells, which are generated by dividing the outer region into intervals along the radial direction, where the target phase changes by 2π, and along the angular direction with a constant angular periodicity. Therefore, the shape of each supercell can be approximated as a rectangle with its size comparable to a wavelength. The arrangement of pillars within this supercell is determined by metagrating optimization via the adjoint method. The optimization process considers both inter-pillar couplings and the range of incidence angles. This makes the design of large-scale wide field-of-view high-efficiency metalenses more tractable than the conventional unit-cell-based method, which is prone to efficiency decrease especially near the lens periphery. Furthermore, it has a potential advantage in terms of computational cost over other recently proposed optimization-based methods.