Superresolution observed from evanescent waves transmitted through nano-corrugated metallic films

TL;DR

This paper investigates how evanescent waves generated by nano-corrugated metallic films can be converted into propagating waves using a microsphere, enabling superresolution imaging of nano-structures.

Contribution

It provides a theoretical analysis of evanescent wave production and their conversion into propagating waves via microspheres, explaining the superresolution mechanism.

Findings

Evanescent waves carry detailed nano-structure information.

Microspheres convert evanescent waves into propagating waves.

High resolution imaging is linked to evanescent wave properties.

Abstract

Plane EM waves transmitted through nano-corrugated metallic thin films produce evanescent waves which include the information on the nano-structures. The production of the evanescent waves at the metallic surface are analyzed. A microsphere located above the metallic surface collects the evanescent waves which are converted into propagating waves. The equations for the refraction at the boundary of the microsphere and the use of Snell's law for evanescent waves are developed. The magnification of the nano-structure images is explained by a geometric optics description, but the high resolution is related to the evanescent waves properties.