Isotropic-medium three-dimensional cloaks for acoustic and electromagnetic waves

TL;DR

This paper introduces a three-dimensional isotropic spherical cloak for acoustic and electromagnetic waves, based on a conformal transformation, which can reduce object visibility within limited angles and restore wave phase in the short-wavelength limit.

Contribution

It generalizes 2D cloaking to 3D using isotropic media, enabling spherical cloaks that operate in transmission mode without mirrors or ground planes.

Findings

Cloak operates in transmission mode with isotropic media.

Restores wave trajectories and phase in the short-wavelength limit.

Applicable to both acoustic and electromagnetic waves.

Abstract

We propose a generalization of the two-dimensional eikonal-limit cloak derived from a conformal transformation to three dimensions. The proposed cloak is a spherical shell composed of only isotropic media; it operates in the transmission mode and requires no mirror or ground plane. Unlike the well-known omnidirectional spherical cloaks, it may reduce visibility of an arbitrary object only for a very limited range of observation angles. In the short-wavelength limit, this cloaking structure restores not only the trajectories of incident rays, but also their phase, which is a necessary ingredient to complete invisibility. Both scalar-wave (acoustic) and transverse vector-wave (electromagnetic) versions are presented.