Reflective Metalenses for Near-Infrared Wavelengths Based on Silicon Nanorods

Abstract

This paper presents the design and analysis of reflective metalenses optimized for a 900 nm wavelength, using silicon nanorods as the primary components. The metalens consists of unit cells, each containing a thin silicon rod. Lumerical FDTD software is used to create a detailed library that connects the dimensions of these nanorods with their respective phase shifts and reflectance properties. The nanorods are placed on a 70 nm thick silicon dioxide (SiO2) layer, with a 50 nm thick gold (Au) reflective layer underneath. In contrast to conventional transmissive metalenses, our design accomplishes complete 2{\pi} phase control via geometry-optimized silicon nanorods, facilitating compact reflective optics. By carefully examining the impact of nanorod dimensions on optical performance, the main goal is to optimize the metalens design for enhanced light focusing and manipulation, which could benefit imaging systems, optical communications, and sensor technology.