# 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.

## Key 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.

---
Source: https://tomesphere.com/paper/1901.05042