Transformation optics

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

Anisotropic Transmission-Line Metamaterials for 2-D Transformation Optics Applications

Abstract: In this contribution, we present a two-dimensional metamaterial unit cell which synthesizes effective material parameters needed for “transformation optics” applications. The metamaterial consists of a grid of reactively loaded transmission-line segments and is a generalization of a previously presented unit cell in that it also synthesizes off-diagonal elements of the permeability tensor. We apply this unit cell to two “transformation optics” applications, a retro-directive reflector, and a cloak. This cloak is different from the so-far reported split-ring-resonator/wire structures in that it not only synthesizes the required μρ and ez distribution but also the μφ one. For the cloak, detailed radar cross-section (RCS) and bandwidth results are presented. It is shown that the total RCS bandwidth is 33.5%, and that losses influence the cloaking performance not critically, pointing to the possibility of practical “transformation optics” designs using the proposed unit cell. Full-wave simulation results of a transmission-line metamaterial cloak in microstrip technology are presented, verifying that the unit cell presented in this paper synthesizes the effective material parameters needed for “transformation optics” or applications that require effective material parameters with off-diagonal tensor elements.

Metamaterials and the Control of Electromagnetic Fields

Abstract: A new class of materials, metamaterials, whose properties are engineered by controlling their nanostructure, open new vistas in optics and offer the possibility of lenses that can resolve details finer than the wavelength of light.

Study of Split-Ring Resonators as a Metamaterial for High-Power Microwave Power Transmission and the Role of Defects

Abstract: Microwave metamaterials show promise in numerous low-power applications, ranging from strip lines to antennas. In general, metamaterials allow microwave designers to obtain electromagnetic characteristics not typically available in nature, leading to new behavior as well as reductions in the size of typical devices. High-power microwave (HPM) sources were efficient in the conventional microwave source community. We consider a specific use of metamaterials as a method to reduce the size of waveguide used for power transmission, particularly, a configuration in which an array of split-ring resonators (SRRs), forming a “mu-negative” structure, allows transmission of power in a waveguide well below the cutoff frequency. This configuration would not be used in an actual HPM device, but explores the methods and considerations that might be required for developing a metamaterial structure for either making HPM sources more compact or developing new types of interaction at these high powers. For any HPM application, a microwave structure must be able to sustain high electric and magnetic fields, as well as high peak and possibly average power. The challenge for metamaterials consists of devising the subwavelength structures (a defining characteristic of metamaterials) that can sustain such fields. In particular, one must understand the sensitivity of any metamaterial system to changes in the individual elements, which in high power pertains mainly to the loss of an individual resonator element. As such a sample system, we explore the physical operating characteristics of the waveguide system loaded with an array of SRRs, particularly the role of defects on its properties. Such defects would form an important feature in any high-power application in which subwavelength structures can be damaged by high field stresses.

Design and experimental demonstration of Doppler cloak from spatiotemporally modulated metamaterials based on rotational Doppler effect.

Abstract: Recently, spatiotemporally modulated metamaterial has been theoretically demonstrated for the design of Doppler cloak, a technique used to cloak the motion of moving objects from the observer by compensating for the Doppler shift. Linear Doppler effect has an angular counterpart, i.e., the rotational Doppler effect, which can be observed by the orbital angular momentum (OAM) of light scattered from a spinning object. In this work, we predict that the spatiotemporally modulated metamaterial has its angular equivalent phenomenon. We therefore propose a technique to observe the rotational Doppler effect by cylindrical spatiotemporally modulated metamaterial. Conversely, such a metamaterial is able to cloak the Doppler shift associated with linear motion by generating an opposite rotational Doppler shift. This novel concept is theoretically analyzed, and a conceptual design by spatiotemporally modulating the permittivity of a voltage-controlled OAM ferroelectric reflector is demonstrated by theoretical calculation and numerical simulation. Finally, a Doppler cloak is experimentally demonstrated by a spinning OAM metasurface in radar system, which the spatiotemporal reflection phase are mechanically modulated. Our work presented in this paper may pave the way for new directions of OAM carrying beams and science of cloaking, and also explore the potential applications of tunable materials and metasurfaces.

Generalized transformation optics from triple spacetime metamaterials

Abstract: In this paper, various extensions of the design strategy for transformation media are proposed. We show that it is possible to assign different transformed spaces to the field strength tensor (electric field and magnetic induction) and to the excitation tensor (displacement field and magnetic field), respectively. In this way, several limitations of standard transformation media can be overcome. In particular, it is possible to provide a geometric interpretation of nonreciprocal as well as indefinite materials. We show that these transformations can be complemented by a continuous version of electric-magnetic duality and comment on the relation to the complementary approach of field-transforming metamaterials.