Theory of Electromagnetic Wave Transmission through Metallic Gratings of Subwavelength Slits

TL;DR

This paper uses FDTD calculations to analyze electromagnetic wave transmission through metallic gratings with subwavelength slits, revealing resonant peaks linked to Rayleigh anomalies and Fabry-Perot resonances, independent of surface plasmons.

Contribution

It provides a theoretical interpretation of transmission enhancement in metallic gratings based on beam anomalies and resonances, differing from surface plasmon explanations.

Findings

Resonant transmission peaks can be up to ten times higher than off-resonance.

Enhancement is explained by Rayleigh anomalies and Fabry-Perot resonances.

Surface plasmon polaritons are not the primary cause of transmission peaks.

Abstract

We present FDTD calculations for transmission of light and other electromagnetic waves through periodic arrays of slits in a metallic slab. The results show resonant, frequency dependent, transmittance peaks for subwavelength widths of the slits which can be up to a factor of ten with respect to those out of resonance. Although our conclusions agree with previous work by Lezec and Thio as regards both the magnitude of the enhancement and the lack of contribution of surface plasmon polaritons of the metal surface to this effect, we derive an interpretation from a theory that deals with emerging beam- Rayleigh anomalies of the grating, and with Fabry-Perot resonances of the perforated slab considered as an effective medium.