High-efficiency broadband achromatic metalens in the visible

TL;DR

This paper presents a novel broadband achromatic metalens in the visible spectrum that achieves high efficiency and polarization independence, enabling advanced imaging and display applications.

Contribution

The work introduces a polarization-independent, high-efficiency broadband achromatic metalens using a minimalist nanofin library and particle swarm optimization.

Findings

Average focusing efficiency of 80.5% across 450-650 nm

Stable focal length with less than 4% deviation

Demonstration of multi-wavelength bi-focal metalens

Abstract

The metalenses have been extensively studied for their compact and flexible characteristics in focusing and imaging applications. However, it remains a significant challenge to design a broadband achromatic metalens that maintains high efficiency under arbitrary polarization incidence. In this work, we design a broadband achromatic metalens that achieves polarization-independent, high-efficiency focusing by effectively utilizing both co-polarization and cross-polarization components of the transmitted light. Using a minimalist anisotropic nanofin library, we optimize the phase distribution of the metalens at each designed wavelength with the particle swarm algorithm. Numerical simulations demonstrate a stable focal length with a deviation of less than 4$\%$ and an average focusing efficiency of 80.5$\%$ in the visible wavelength range of 450 to 650 nm. Moreover, we design a multi-wavelength off-axis bi-focal metalens to demonstrate the flexible control of output light phase and dispersion achieved by this method. The generality of this design enables its implementation in various metasurface devices, accelerating applications in broadband imaging and virtual/augmented reality.