Demonstration of focal length tuning by rotational varifocal moir\'e metalens in an ir-A wavelength

TL;DR

This paper demonstrates a moiré metalens with wide focal length tunability from negative to positive by rotating the lens, using high contrast amorphous silicon meta-atoms at 900 nm wavelength, enabling adjustable optical focusing.

Contribution

It introduces a moiré metalens with polarization insensitivity and full phase coverage, achieving wide focal length tuning through mutual rotation at near-infrared wavelengths.

Findings

Focal length tunability between ±1.73 mm and ±5 mm.

Optical power range from ±578 to ±200 m$^{-1}$.

Achieved tunability by mutual rotation at ±90 degrees.

Abstract

This paper reports an experimental demonstration of moir\'e metalens which shows wide focal length tunability from negative to positive by mutual angle rotation at the wavelength of 900 nm. The moir\'e metalens was developed using high index contrast transmitarray meta-atoms made of amorphous silicon octagonal pillars, which is designed to have polarization insensitivity and full 2$\pi$ phase coverage. The fabricated moir\'e metalens showed focal length tunability at the ranges between $\pm$1.73 -- $\pm$5 mm, which corresponds to the optical power ranges between $\pm$578 -- $\pm$200 m$^{-1}$ at the mutual rotation between $\pm$90 degrees.