Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics

TL;DR

This paper investigates the photorealistic rendering of free-space invisibility cloaks made of uniaxial dielectrics, revealing performance limitations and promising results for azimuthal configurations through ray tracing simulations.

Contribution

It introduces and analyzes two new uniaxial dielectric cylindrical cloaks, including the novel azimuthal uniaxial design, using photorealistic ray tracing to evaluate their cloaking performance.

Findings

Cloaking is ineffective for horizontal and ordinary linear polarizations.

Viewing-angle-dependent aberrations affect cloaking performance.

Azimuthal uniaxial cloak shows surprisingly good cloaking performance.

Abstract

The design rules of transformation optics generally lead to spatially inhomogeneous and anisotropic impedance-matched magneto-dielectric material distributions for, e.g., free-space invisibility cloaks. Recently, simplified anisotropic non-magnetic free-space cloaks made of a locally uniaxial dielectric material (calcite) have been realized experimentally. In a two-dimensional setting and for in-plane polarized light propagating in this plane, the cloaking performance can still be perfect for light rays. However, for general views in three dimensions, various imperfections are expected. In this paper, we study two different purely dielectric uniaxial cylindrical free-space cloaks. For one, the optic axis is along the radial direction, for the other one it is along the azimuthal direction. The azimuthal uniaxial cloak has not been suggested previously to the best of our knowledge. We visualize the cloaking performance of both by calculating photorealistic images rendered by ray tracing. Following and complementing our previous ray-tracing work, we use an equation of motion directly derived from Fermats principle. The rendered images generally exhibit significant imperfections. This includes the obvious fact that cloaking does not work at all for horizontal or for ordinary linear polarization of light. Moreover, more subtle effects occur such as viewing-angle-dependent aberrations. However, we still find amazingly good cloaking performance for the purely dielectric azimuthal uniaxial cloak.