Optical Superoscillatory Poisson-Arago Spots

TL;DR

This paper demonstrates that a simple single-disc setup can generate diffraction-unlimited superoscillatory spots, overcoming the optical diffraction limit and enabling ultra-narrow, long, non-diffracting light beams with potential broad applications.

Contribution

It introduces a novel, simple approach using a single disc to produce superoscillatory spots, bypassing complex metamaterial designs and near-field limitations.

Findings

Achieved diffraction-unlimited spots down to λ/20 size.

Created ultra-long, nearly nondiffracting superoscillatory needles.

Provided a simple, fabricable element for surpassing the diffraction limit.

Abstract

Optical diffraction limit has been a long-term scientific issue since Ernst Abbe first introduced the concept in 1873. It is a constraint on the smallest light spot that can be achieved. Substantial effort has been invested in the past decade to beat this limit by exploiting evanescent waves. But this method encounters serious near-field limitations. A more promising route to breaking the constraint is to explore optical superoscillation in the far field with engineered metamaterials. However, these particular structures involve with very complicated optimization-based design that requires precisely tailoring the interference of propagating waves with low spatial frequency. To overcome these limitations, here we explore a new approach based on the two-hundred-year-old discovery: Possion-Arago spots. We show for the first time that by using a single disc, constructive interference of propagating waves with high-spatial-frequency wavevectors can be realized, generating a diffraction-unlimited localized Possion-Arago spot with achievable size down to $\lambda/$20. Actually, such an element permits creation of an ultra-long nearly nondiffracting superoscillatory needle with appreciable field of view. This easy-to-fabrication element provides a promising route to overcome the diffraction limit, thus might open new avenues to exploit various applications in different fields.