Eigen modes for the problem of anomalous light transmission through subwavelength holes

TL;DR

This paper reveals new eigen-modes with complex propagation constants in metal-dielectric structures, crucial for understanding anomalous light transmission through subwavelength holes, challenging traditional lossless waveguide concepts.

Contribution

It introduces a new class of eigen-modes with complex values in metal-dielectric structures, expanding the understanding of light transmission phenomena.

Findings

Identification of new eigen-states with complex propagation constants

Demonstration that traditional eigen-mode concepts fail in metal-dielectric structures

Highlighting the importance of anomalous modes in subwavelength hole transmission

Abstract

We show that the wide-spread concept of optical eigen modes in lossless waveguide structures, which assumes the separation on propagating and evanescent modes, fails in the case of metal-dielectric structures, including photonic crystals. In addition to these modes, there is a sequence of new eigen-states with complex values of the propagation constant and non-vanishing circulating energy flow. The whole eigen-problem ceases to be hermitian because of changing sign of the optical dielectric constant. The new anomalous modes are shown to be of prime importance for the description of the anomalous light transmission through subwavelength holes.