Abstract
Grating cloaks are a variation of dielectric carpet (or ground-plane) cloaks. The latter were introduced by Li and Pendry. In contrast to the numerical work involved in the quasi-conformal carpet cloak, the refractive-index profile of a conformal grating cloak follows a closed and exact analytical form. We have previously mentioned that finite-size conformal grating cloaks may exhibit better cloaking than usual finite-size carpet cloaks. In this paper, we directly visualize their performance using photorealistic ray-tracing simulations. We employ a Newtonian approach that is advantageous compared to conventional ray tracing based on Snell's law. Furthermore, we quantify the achieved cloaking quality by computing the cross-correlations of rendered images. The cross-correlations for the grating cloak are much closer to 100% (i.e., ideal) than those for the Gaussian carpet cloak.
Highlights
The concept of transformation optics [1,2,3,4,5] has firmly established that arbitrary objects can be made to appear invisible by surrounding them with an appropriately shaped inhomogeneous and generally anisotropic optical magneto-dielectric structure
The carpet cloak does suffer from certain limitations, such as a pronounced lateral beam displacement [13]
Photorealistic ray tracing [16,17,18] is a well-known rendering technique based on ray optics, allowing to simulate images as they would appear to the human eye, and providing a direct and intuitive impression of their performance
Summary
The concept of transformation optics [1,2,3,4,5] has firmly established that arbitrary objects can be made to appear invisible by surrounding them with an appropriately shaped inhomogeneous and generally anisotropic optical magneto-dielectric structure. The lateral beam displacement disappears almost completely for a single non-zero spatial frequency component We have called this configuration the grating cloak [15]. Photorealistic ray tracing [16,17,18] is a well-known rendering technique based on ray optics, allowing to simulate images as they would appear to the human eye, and providing a direct and intuitive impression of their performance. These images can be the basis for a quantitative assessment of the cloaking quality using cross-correlation functions (see section 5). To obtain fully converged results under these conditions, we employ Newtonian ray tracing in a dedicated home-built software program
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