Metallic nanolayers -- a sub-visible wonderland of optical properties

TL;DR

Ultra-thin metallic nanolayers exhibit unique optical properties such as high reflectivity and equal transmittance and reflectance at nanometer scales, with potential applications in various optical technologies.

Contribution

This paper reviews the electromagnetic theory of metallic nanolayers and presents new experimental and theoretical insights into their unusual optical behaviors.

Findings

Nanolayers remain highly reflective even when much thinner than skin depth.

At a few nanometers thickness, reflectivity equals transmittivity and absorption peaks at 50%.

Experimental confirmation of predicted optical properties.

Abstract

It was predicted long ago that ultra-thin metallic films must exhibit unusual optical properties for radiation frequencies from rf to infrared domain. A film would remain highly reflective even when it is orders of magnitude thinner than a skin depth at any frequency. Only when it is a few nanometers thick (depending on material but not on the frequency), its reflectivity and transmittivity get equal, while its absorption peaks at 50%. It has been confirmed experimentally and new directions and applications were proposed. We review the EM theory of the phenomenon and recent developments in the field, and present some new results.