# Achromatic super-oscillatory lenses with sub-wavelength focusing

## TL;DR

This paper introduces achromatic super-oscillatory lenses capable of focusing light into sub-wavelength hotspots across multiple wavelengths, overcoming traditional chromatic and diffraction limitations with a compact, planar design.

## Contribution

The authors present a novel single-element planar lens design that achieves sub-wavelength focusing and chromatic correction using super-oscillations, fabricated on various substrates for visible and infrared light.

## Key findings

- Successfully fabricated super-oscillatory lenses on silicon wafers and silica substrates.
- Achieved sub-wavelength focusing across multiple wavelengths.
- Lenses are low-cost, compact, and suitable for various technological applications.

## Abstract

Lenses are crucial to light-enabled technologies. Conventional lenses have been perfected to achieve near-diffraction-limited resolution and minimal chromatic aberrations. However, such lenses are bulky and cannot focus light into a hotspot smaller than half wavelength of light. Pupil filters, initially suggested by Toraldo di Francia, can overcome the resolution constraints of conventional lenses, but are not intrinsically chromatically corrected. Here we report single-element planar lenses that not only deliver sub-wavelength focusing (beating the diffraction limit of conventional refractive lenses) but also focus light of different colors into the same hotspot. Using the principle of super-oscillations we designed and fabricated a range of binary dielectric and metallic lenses for visible and infrared parts of the spectrum that are manufactured on silicon wafers, silica substrates and optical fiber tips. Such low cost, compact lenses could be useful in mobile devices, data storage, surveillance, robotics, space applications, imaging, manufacturing with light, and spatially resolved nonlinear microscopies.

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Source: https://tomesphere.com/paper/1701.06863