Dielectric metalens with reduced meta-atom aspect ratio and high focusing efficiency

Abstract

Metalenses have shown their great ability in efficient manipulation of light fields and have been proposed for variety of devices with specific functionalities making the world more compact and flatter. However, a high meta-atom aspect ratio is still a drawback as it causes difficulty in fabrication of metalens. In this paper, we propose a design principle to lower the meta-atom aspect ratio in near infrared region. The designed metalens is made by arranging hollow cylindrical nanopillars made up of crystalline Silicon and the substrate is of material SiO₂. The simulation results show that the required aspect ratio of our design is much smaller than that of solid single material meta-atom thus without compromising with the transmission efficiency of the meta-atom. Also, the designed metalens have a high focusing efficiency of nearly 90% and with polarization independent characteristics. Our proposed design may pave the way towards easier fabrication and thus application of near infrared devices.