Metalenses with polarization-independent adaptive nano-antennas

TL;DR

This paper introduces polarization-insensitive nano-antennas and a non-uniform unit cell arrangement to create high-efficiency, high-NA metalenses capable of advanced imaging, surpassing previous polarization-dependent designs.

Contribution

The work presents a novel design of polarization-insensitive dimer nano-antennas and abandons uniform spacing, achieving ultrahigh NA and efficiency in visible wavelengths.

Findings

Achieved polarization-independent metalenses with NA=1.48 and 43% efficiency.

Demonstrated confocal microscopy imaging with 300 nm resolution at 532 nm.

Significantly improved polarization-insensitive metalens performance.

Abstract

Metalens research has made major advances in recent years. These advances rely on the simple design principle of arranging meta-atoms in regular arrays to create an arbitrary phase and polarization profile. Unfortunately, the concept of equally spaced meta-atoms reaches its limit for high deflection angles where the deflection efficiency decreases. The efficiency can be increased using nano-antennas with multiple elements, but their polarization sensitivity hinders their application in metalenses. Here, we show that by designing polarization-insensitive dimer nano-antennas and abandoning the principle of equally spaced unit cells, polarization-independent ultrahigh numerical aperture (NA=1.48) oil-immersion operation with an efficiency of 43% can be demonstrated. This represents a significant improvement on other polarization-independent designs at visible wavelength. We also use this single layer metalens to replace a conventional objective lens and demonstrate the confocal scanning microscopic imaging of a grating with a period of 300 nm at 532 nm operating wavelength. Overall, our results experimentally demonstrate a novel design concept that further improves metalens performance.