Resonant absorption of electromagnetic waves in transition anisotropic media

TL;DR

This paper investigates how electromagnetic waves are absorbed and converted in a stratified anisotropic medium with tilted optical axes, revealing conditions for resonant absorption and the effects of medium hyperbolicity on wave transmission.

Contribution

It introduces a detailed analysis of mode conversion and resonant absorption in tilted anisotropic media using invariant imbedding theory, highlighting the impact of medium hyperbolicity on absorption enhancement.

Findings

Resonant absorption is significantly enhanced in hyperbolic media.

Asymmetry in transmission and absorption occurs with nonzero tilt angles.

Sharp peaks in transmittance and absorptance are observed at specific incident angles.

Abstract

We study the mode conversion and resonant absorption phenomena occurring in a slab of a stratified anisotropic medium, optical axes of which are tilted with respect to the direction of inhomogeneity, using the invariant imbedding theory of wave propagation. When the tilt angle is zero, mode conversion occurs if the longitudinal component of the permittivity tensor, which is the one in the direction of inhomogeneity in the non-tilted case, varies from positive to negative values within the medium, while the transverse component plays no role. When the tilt angle is nonzero, the wave transmission and absorption show an asymmetry under the sign change of the incident angle in a range of the tilt angle, while the reflection is always symmetric. We calculate the reflectance, the transmittance and the absorptance for several configurations of the permittivity tensor and find that resonant absorption is greatly enhanced when the medium from the incident surface to the resonance region is hyperbolic than when it is elliptic. For certain configurations, the transmittance and absorptance curves display sharp peaks at some incident angles determined by the tilt angle.