Role of commensurate arrangements in the optical response of metallic gratings

TL;DR

This paper investigates how commensurate arrangements of metallic sub-wavelength grooves influence light localization, revealing new states that emerge as arrangements approach irrational ratios, with experimental validation in the infrared spectrum.

Contribution

It introduces a theoretical framework showing new light localization states in commensurate metallic gratings and provides experimental evidence supporting these predictions.

Findings

New light localization states are produced near irrational commensuration ratios.

Experimental reflectivity measurements confirm theoretical predictions.

Localized light states resemble hot spots on disordered surfaces.

Abstract

Light localization on commensurate arrangements of metallic sub-wavelength grooves is studied. We theoretically show that as the degree of commensuration tends to an irrational number new light localization states are produced. These have properties close to that reported for hot spots on disordered surfaces and are not permitted for simple period gratings. Some theoretical predictions are experimentally provided in the infra-red region by reflectivity measurements performed on two commensurate samples with respectively two and three slits per period.