Transformation optics

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

Magnetoelastic nonlinear metamaterials

Abstract: We introduce the concept of magnetoelastic metamaterials with electromagnetic properties depending on elastic deformation. We predict a strong nonlinear and bistable response of such metamaterials caused by their structural reshaping in response to the applied electromagnetic field. In addition, we demonstrate experimentally the feasibility of the predicted effect.

Broadband electromagnetic cloaking with smart metamaterials

Abstract: The ability to render objects invisible with a cloak that fits all objects and sizes is a long-standing goal for optical devices. Invisibility devices demonstrated so far typically comprise a rigid structure wrapped around an object to which it is fitted. Here we demonstrate smart metamaterial cloaking, wherein the metamaterial device not only transforms electromagnetic fields to make an object invisible, but also acquires its properties automatically from its own elastic deformation. The demonstrated device is a ground-plane microwave cloak composed of an elastic metamaterial with a broad operational band (10-12 GHz) and nearly lossless electromagnetic properties. The metamaterial is uniform, or perfectly periodic, in its undeformed state and acquires the necessary gradient-index profile, mimicking a quasi-conformal transformation, naturally from a boundary load. This easy-to-fabricate hybrid elasto-electromagnetic metamaterial opens the door to implementations of a variety of transformation optics devices based on quasi-conformal maps.

A broadband low-reflection metamaterial absorber

Abstract: Artificially engineered metamaterials have enabled the creation of electromagnetic materials with properties not found in nature. Recent work has demonstrated the feasibility of developing high performance, narrowband electromagnetic absorbers using such metamaterials. These metamaterials derive their absorption properties primarily through dielectric loss and impedance matching at resonance. This paper builds on that work by increasing the bandwidth through embedding resistors into the metamaterial structure in order to lower the Q factor and by using multiple elements with different resonances. This is done while maintaining an impedance-matched material at normal incidence. We thus present the design, simulation, and experimental verification of a broadband gigahertz region metamaterial absorber, with a maximum absorption of 99.9% at 2.4 GHz, and a full width at half maximum bandwidth of 700 MHz, all while maintaining low reflection inside and outside of resonance.

Dielectric metamaterials with toroidal dipolar response

Abstract: Toroidal multipoles are the terms missing in the standard multipole expansion; they are usually overlooked due to their relatively weak coupling to the electromagnetic fields. Here, we propose and theoretically study all-dielectric metamaterials of a special class that represent a simple electromagnetic system supporting toroidal dipolar excitations in the THz part of the spectrum. We show that resonant transmission and reflection of such metamaterials is dominated by toroidal dipole scattering, the neglect of which would result in a misunderstanding interpretation of the metamaterials’ macroscopic response. Because of the unique field configuration of the toroidal mode, the proposed metamaterials could serve as a platform for sensing or enhancement of light absorption and optical nonlinearities.

Description and explanation of electromagnetic behaviors in artificial metamaterials based on effective medium theory

Abstract: We present a general theory of effective media to set up the relationship between the particle responses and the macroscopic system behaviors for artificial metamaterials composed of periodic resonant structures. By treating the unit cell of the periodic structure as a particle, we define the average permittivity and permeability for different unit structures and derive a general form of discrete Maxwell's equations on the macroscale, from which we obtain different wave modes in metamaterials including the propagation mode, pure plasma mode, and resonant crystal band-gap mode. We explain unfamiliar behaviors of metamaterials from the numerical S parameter retrieval approach. The excellent agreement between theoretical predictions and retrieval results indicates that the defined model and method of analysis fit the physical structures very well. Thereafter, we propose a more advanced form of the fitting formulas for the effective electromagnetic parameters of metamaterials.