Counterposition and negative phase velocity in uniformly moving dissipative materials

TL;DR

This study investigates how uniform motion of dissipative dielectric materials affects electromagnetic wave refraction, phase velocity, and beam displacement, revealing controllable phenomena like negative phase velocity and lateral beam shifts.

Contribution

It demonstrates that observer velocity can alter phase velocity, counterposition, and beam position in moving dissipative materials, introducing new ways to control electromagnetic wave behavior.

Findings

Observer velocity can switch phase velocity from positive to negative.

Lateral beam displacement can be controlled by observer motion.

Transmittance in moving dissipative slabs is generally very low.

Abstract

The Lorentz transformations of electric and magnetic fields were implemented to study (i) the refraction of linearly polarized plane waves into a half-space occupied by a uniformly moving material, and (ii) the traversal of linearly polarized Gaussian beams through a uniformly moving slab. Motion was taken to occur tangentially to the interface(s) and in the plane of incidence. The moving materials were assumed to be isotropic, homogeneous, dissipative dielectric materials from the perspective of a co-moving observer. Two different moving materials were considered: from the perspective of a co-moving observer, material A supports planewave propagation with only positive phase velocity, whereas material B supports planewave propagation with both positive and negative phase velocity, depending on the polarization state. For both materials A and B, the sense of the phase velocity and whether or not counterposition occurred, as perceived by a nonco-moving observer, could be altered by varying the observer's velocity. Furthermore, the lateral position of a beam upon propagating through a uniformly moving slab made of material A, as perceived by a nonco-moving observer, could be controlled by varying the observer's velocity. In particular, at certain velocities, the transmitted beam emerged from the slab laterally displaced in the direction opposite to the direction of incident beam. The transmittances of a uniformly moving slab made of material B were very small and the energy density of the transmitted beam was largely concentrated in the direction normal to the slab, regardless of the observer's velocity.