Metalenses with Polarization‐Insensitive Adaptive Nano‐Antennas

Abstract

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, it is shown that by designing polarization‐insensitive dimer nano‐antennas and abandoning the principle of equally spaced unit cells, polarization‐insensitive ultrahigh numerical aperture (NA = 1.48) oil‐immersion operation with an efficiency of 42% can be demonstrated. This represents a significant improvement on other polarization‐insensitive designs at visible wavelength. This single layer metalens is used to replace a conventional objective lens and demonstrates the confocal scanning microscopic imaging of a grating with a period of 300 nm at 532 nm operating wavelength. Overall, the results experimentally demonstrate a novel design concept that further improves metalens performance.