No abstract

In the propagation phase of a dielectric metasurface, there are two important problems. Firstly, the range of transmittance of the nanopillars for a building metasurface is usually between 60% and 100%, which reduces the metasurface’s overall transmittance and affects the uniformity of the transmitted light. Secondly, the realistic phase provided by the nanopillar cannot be matched very well with the theoretical phase at each lattice location.The phase difference (between a realistic phase and theoretical phase) may reach tens of degrees. Here, we propose an interesting method to solve these problems. With this new method, a metalens is designed in this paper. The nanopillars for building the metalens have transmittance over 0.95, which increases the metalens transmittance and improves the light uniformity. In addition, with the new method, the phase differences of all elements in the metalens can also be reduced to be below 0.05°, decreasing the metalens spherical aberration dramatically. This method not only helps us to optimize the metalens but also provides a useful way for designing high-quality metasurfaces.

We propose a dual-function metasurface with a chiral double L-type silicon meta-atom that works in the near-infrared band. On one hand, the designed metasurface can achieve the function of a quarter-wave plate in the wavelength of 1660–1840 nm, and convert y -linear polarization (LP) light into right-hand circular polarization (RCP) light. The polarization conversion ratio (PCR) is above 90%, up to 98%, and the ellipticity of the transmitted light is 0.9–1.0. On the other hand, for a wavelength of 1497 nm, the designed structure can also convert LP in any direction to left-hand circular polarization (LCP) light by using the circular dichroism of chiral structures. The PCR is above 99%, and the ellipticity of the transmitted light is equal to approximately − 1 . Moreover, when incident in the opposite direction, the wave plate can convert LP to RCP light. At present, the all-dielectric metasurface has important application potential in polarization conversion and photonic integration.