Transformation optics

About: Transformation optics is a research topic. Over the lifetime, 2687 publications have been published within this topic receiving 102378 citations.

Photorealistic rendering of unidirectional free-space invisibility cloaks.

Abstract: Carpet or ground-plane invisibility cloaks hide an object in reflection and inhibit transmission experiments by construction. This concept has significantly reduced the otherwise demanding material requirements and has hence enabled various experimental demonstrations. In contrast, free-space invisibility cloaks should work in both reflection and transmission. The fabrication of omnidirectional three-dimensional free-space cloaks still poses significant challenges. Recently, the idea of the carpet cloak has been carried over to experiments on unidirectional free-space invisibility cloaks that only work perfectly for one particular viewing direction and, depending on the design, also for one linear polarization of light only. Here, by using photorealistic ray tracing, we visualize the performance of four types of such unidirectional cloaks in three dimensions for different viewing directions and different polarizations of light, revealing virtues and limitations of these approaches in an intuitive manner.

Diamond-shaped electromagnetic transparent devices with homogeneous material parameters

Abstract: Based on the linear coordinate transformation method, two-dimensional and three-dimensional electromagnetic transparent devices with diamond shape composed of homogeneous and non-singular materials are proposed in this paper. The permittivity and permeability tensors of the transparent devices are derived. The performance and scattering properties of the transparent devices are confirmed by a full-wave simulation. It can physically protect electric devices such as an antenna and a radar station inside, without sacrificing their performance. This work represents important progress towards the practical realization of metamaterial-assisted transparent devices and expands the application of transformation optics.

Water based fluidic radio frequency metamaterials

Abstract: Electromagnetic metamaterials offer great flexibility for wave manipulation and enable exceptional functionality design, ranging from negative refraction, anomalous reflection, super-resolution imaging, transformation optics to cloaking, etc. However, demonstration of metamaterials with unprecedented functionalities is still challenging and costly due to the structural complexity or special material properties. Here, we demonstrate for the first time the versatile fluidic radio frequency metamaterials with negative refraction using a water-embedded and metal-coated 3D architecture. Effective medium analysis confirms that metallic frames create an evanescent environment while simultaneously water cylinders produce negative permeability under Mie resonance. The water-metal coupled 3D architectures and the accessory devices for measurement are fabricated by 3D printing with post electroless deposition. Our study also reveals the great potential of fluidic metamaterials and versatility of the 3D printing proc...

The KdV hierarchy in optics

Abstract: Transformation optics [1, 2] has contributed greatly to our understanding of wave propagation in inhomogeneous media, providing a simple intuitive recipe for relating material properties to analytical solutions. It makes use of the fact that Maxwell's equations in a transformed coordinate system take the same form as Maxwell's equations in an inhomogeneous anisotropic medium. In this talk I shall discuss the application of a different equivalence that is embedded in Maxwell's equations. This is the equivalence of the scattering from a planar medium, if the properties of that medium are evolved according to the Korteweg-de Vries equation [3]. Given the lack of many general statements one can make about wave propagation through inhomogeneous media, one line of attack is to separate out the possible functions ϵ(x) into families that have closely related scattering properties. Take for example monochromatic electromagnetic waves polarized along z and propagating in the x-y plane through an inhomogeneous slab with complex permittivity ϵ s (x) = 1 + u s (x). These are governed by the Helmholtz equation equation where φ s is the electric field amplitude, k y = k 0 sin(θ) is the in-plane wavevector determining the angle of incidence θ, and u s (x) → 0 as |x| → ∞. The subscript ‘s’ on the permittivity labels one of a continuous family of inhomogeneous media (schematic shown in Figure 1).

Designing flexible and versatile metamaterial absorbers

Abstract: Absorbers play an important role in protecting sensitive electronic devices from electromagnetic interference by absorbing the energy of incoming waves and reducing unnecessary reflection or transmission. In this paper we introduce new types of absorbers based on periodic structures, or the so-called metamaterials, which give us additional degrees of freedom to design the absorbing performance of absorbers with reduced thicknesses. Specifically, we demonstrate two types of metamaterial absorbers: one allowing us to customize absorption and other scattering parameters at selected frequencies; another absorbing only high-power microwaves and transmitting small signals even at the same frequency to maintain wireless communications. These metamaterial absorbers are expected to facilitate solving modern, complex EM interference issues where different-interdependent requirements exist.