Simple and polarization-independent Dammann grating based on all-dielectric nanorod array

Abstract

In this work, we comprehensively investigate a Dammann grating (DG) that can generate a 5 × 5 diffraction spot array with an extending angle of around the fiber communication wavelength of . The DG is a simple metasurface structure composed of a silicon cuboid nanorod array on a silica substrate, and only two different sizes of nanorods with square cross-sections and uniform spatial orientations are used. These simple units and this configuration are favorable in practice, and the C4 symmetry cross section of the nanorods ensures the polarization-independent operation of the DG. The phase modulation of the nanorods is achieved by the guiding mode propagating in them rather than electric or magnetic Mie-type resonance, which makes the design of the cuboid nanorods easy and robust. More importantly, the two-dimensional nanorod array is generated from a one-dimensional array, which further decreases the design and fabrication complexity.