# Electromagnetic surface waves guided by the planar interface of isotropic chiral materials

## TL;DR

This study investigates electromagnetic surface waves at the interface of two isotropic chiral materials, analyzing how their propagation depends on material composition and complex permittivity, revealing conditions for surface wave support.

## Contribution

It introduces a numerical analysis of surface wave propagation at isotropic chiral interfaces, considering the effects of homogenized composite materials and varying permittivity.

## Key findings

- Surface waves exist only within specific volume fraction ranges.
- Surface wave characteristics depend on the real and imaginary parts of permittivity.
- Different behaviors are observed for positive and negative real permittivity cases.

## Abstract

The propagation of electromagnetic surface waves guided by the planar interface of two isotropic chiral materials, namely materials $\calA$ and $\calB$, was investigated by numerically solving the associated canonical boundary-value problem. Isotropic chiral material $\calB$ was modeled as a homogenized composite material, arising from the homogenization of an isotropic chiral component material and an isotropic achiral, nonmagnetic, component material characterized by the relative permittivity $\eps_a^\calB$. Changes in the nature of the surface waves were explored as the volume fraction $f_a^\calB$ of the achiral component material varied. Surface waves are supported only for certain ranges of $f_a^\calB$; within these ranges only one surface wave, characterized by its relative wavenumber $q$, is supported at each value of $f_a^\calB$. For $\mbox{Re} \lec \eps_a^\calB \ric > 0 $, as $\left| \mbox{Im} \lec \eps_a^\calB \ric \right|$ increases surface waves are supported for larger ranges of $f_a^\calB$ and $\left| \mbox{Im} \lec q \ric \right|$ for these surface waves increases. For $\mbox{Re} \lec \eps_a^\calB \ric < 0 $, as $ \mbox{Im} \lec \eps_a^\calB \ric $ increases the ranges of $f_a^\calB$ that support surface-wave propagation are almost unchanged but $ \mbox{Im} \lec q \ric $ for these surface waves decreases. The surface waves supported when $\mbox{Re} \lec \eps_a^\calB \ric < 0 $ may be regarded as akin to surface-plasmon-polariton waves, but those supported for when $\mbox{Re} \lec \eps_a^\calB \ric > 0 $ may not.