Metalenses at visible wavelengths: past, present, perspectives

TL;DR

This paper reviews the development, current state, and future prospects of metalenses operating at visible wavelengths, highlighting technological challenges and design considerations for high-efficiency flat optical devices.

Contribution

It provides a comprehensive overview of the history, current advancements, and future perspectives in visible-wavelength metalenses, emphasizing design and material challenges.

Findings

High-efficiency metalenses require low absorption materials.

Achieving large deflection angles demands precise nanostructure engineering.

Technological and material innovations are crucial for future improvements.

Abstract

The so-called "flat optics" that shapes the phase of an incident wave in free space through subwavelength structures has a venerable history. In that domain, achieving high efficiency at large deflection angles requires a low absorption material, a suitable technological process, as well as suitably engineered nanostructures that makes them electromagnetically independent despite the small spacing required to spatially sample a rapidly varying phase.