Highly tunable elastic dielectric metasurface lenses

TL;DR

This paper introduces a highly tunable elastic dielectric metasurface lens made of silicon nano-posts in an elastic polymer, capable of adjusting focal length significantly while maintaining high efficiency, enabling versatile ultra-thin optical devices.

Contribution

The work presents a novel elastic metasurface lens with tunable focal length, demonstrating significant flexibility and high efficiency, which was not achievable with previous fixed-function metasurfaces.

Findings

Focal length tunable from 600 μm to 1400 μm via radial strain.

Maintains diffraction-limited focus and over 50% focusing efficiency.

Operates effectively at 915 nm wavelength.

Abstract

Dielectric metasurfaces are two-dimensional structures composed of nano-scatterers that manipulate phase and polarization of optical waves with subwavelength spatial resolution, enabling ultra-thin components for free-space optics. While high performance devices with various functionalities, including some that are difficult to achieve using conventional optical setups have been shown, most demonstrated components have a fixed functionality. Here we demonstrate highly tunable metasurface devices based on subwavelength thick silicon nano-posts encapsulated in a thin transparent elastic polymer. As proof of concept, we demonstrate a metasurface microlens operating at 915 nm, with focal distance tuning from 600 $\mu$m to 1400 $\mu$m through radial strain, while maintaining a diffraction limited focus and a focusing efficiency above 50$\%$. The demonstrated tunable metasurface concept is highly versatile for developing ultra-slim, multi-functional and tunable optical devices with widespread applications ranging from consumer electronics to medical devices and optical communications.