Imaging with flat optics: metalenses or diffractive lenses?

TL;DR

This paper compares metalenses and diffractive lenses, showing that properly designed multi-level diffractive lenses can outperform metalenses in imaging, with advantages in manufacturing and size, while metalenses excel in polarization control.

Contribution

It demonstrates that multi-level diffractive lenses can surpass metalenses in performance and are easier to manufacture at large scales, clarifying their respective advantages.

Findings

MDLs can exceed metalenses in imaging performance

MDLs are suitable for low-cost, large-area manufacturing

Thickness advantage of metalenses is minimal due to substrate dominance

Abstract

Recently, there has been an explosion of interest in metalenses for imaging. The interest is primarily based on their sub-wavelength thicknesses. Diffractive lenses have been used as thin lenses since the late 19th century. Here, we show that multi-level diffractive lenses (MDLs), when designed properly can exceed the performance of metalenses. Furthermore, MDLs can be designed and fabricated with larger constituent features, making them accessible to low-cost, large area volume manufacturing, which is generally challenging for metalenses. The support substrate will dominate overall thickness for all flat optics. Therefore the advantage of a slight decrease in thickness (from ~2{\lambda} to ~{\lambda}/2) afforded by metalenses may not be useful. We further elaborate on the differences between these approaches and clarify that metalenses have unique advantages when manipulating the polarization states of light.