Achromatic Metalens in the Visible and Metalens with Reverse Chromatic Dispersion

TL;DR

This paper reports the experimental development of an achromatic metalens operating across visible wavelengths and introduces a metalens with reverse chromatic dispersion, enabling new optical applications.

Contribution

The work demonstrates a novel dispersion engineering approach for achromatic metalenses and designs a metalens with reverse chromatic dispersion, expanding functional capabilities.

Findings

Achromatic metalens operates from 490 nm to 550 nm in reflection mode.

Metalens with reverse chromatic dispersion increases focal length with wavelength.

Potential applications include LED illumination imaging and spectroscopy.

Abstract

In this letter, we experimentally report an achromatic metalens (AML) operating over a continuous bandwidth in the visible. This is accomplished via dispersion engineering of dielectric phase shifters: titanium dioxide nanopillars tiled on a dielectric spacer layer above a metallic mirror. The AML works in reflection mode with a focal length independent of wavelength from wavelength of 490 nm to 550 nm. We also design a metalens with reverse chromatic dispersion, where the focal length increases as the wavelength increases, contrary to conventional diffractive lenses. The ability to engineer the chromatic dispersion of metalenses at will enables a wide variety of applications that were not previously possible. In particular, for the AML design, we envision applications such as imaging under LED illumination, fluorescence, and photoluminescence spectroscopy.