Consequences of nonreciprocity in reflection from a truncated spatial Kramers-Kronig medium

TL;DR

This paper investigates how nonreciprocity in a truncated Kramers-Kronig medium affects reflection, scattering, and surface wave properties, revealing unique unidirectional behaviors and surface plasmon modes due to inherent asymmetry.

Contribution

It demonstrates that a finite KK medium slab supports one-sided null scattering and unidirectional surface plasmons, highlighting the effects of nonreciprocity and asymmetry in wave interactions.

Findings

Finite KK slab supports one-sided null scattering.

Null scattering can be achieved on the opposite side with phase lag.

Surface TM modes exist only for illumination from one side.

Abstract

We study the truncated Kramers-Kronig (KK) medium to reveal the effects of nonreciprocity in reflection on the scattering and the wave guiding properties. We focus on the simplest possible spatial profile mimicking the dielectric response. We show that a finite slab of KK medium can support only one sided null scattering under bidirectional identical illumination. However, for a phase lag between the two incident beams it is possible to have null scattering on the other side. This is shown to be a consequence of the nonreciprocity in reflection due to the inherent asymmetry of the KK medium. We further look at the possibility of surface modes for unidirectional illumination. For specific range of parameters, we show the existence of TM polarized surface plasmons only for illumination from one side. The origin of such modes is traced to the inhomogeneous metal like layer with negative real part of the permittivity in the KK medium.