Design, Modeling, and Measurement of a Metamaterial Electromagnetic Field Concentrator

This document addresses the need to improve the design process for creating an optimized metamaterial. In particular, two challenges are addressed: creating an electromagnetic concentrator and optimizing the design of metamaterial used to create the electromagnetic concentrator. The first challenge is addressed by developing an electromagnetic field concentrator from a design of concentric geometric shapes. The material forming the concentrator is derived from the application of transformation optics. The resulting anisotropic, spatially variant constitutive parameter tensors are then approximated with metamatieral inclusions using the combination of an AFIT rapid metamaterial design process and a design process created for rapid metamaterial production. The second challenge of optimizing the design of the metamaterial is addressed by considering factors such as circuit board selection, various sets of metamaterial cell geometry combinations, and optimization of the ratio of the widths for the concentric geometric shapes. The resulting optimized design is simulated and shown to compress and concentrate the vertical electric field component of incident plane waves. A physical device is constructed based on the simulations and tested to confirm the entire design process. Experimental data do not definitely show concentration however an optimized design process has been proven

Illusion optics: The optical transformation of an object into another object

We propose to use transformation optics to generate a general illusion such that an arbitrary object appears to be like some other object of our choice. This is achieved by using a remote device that transforms the scattered light outside a virtual boundary into that of the object chosen for the illusion, regardless of the profile of the incident wave. This type of illusion device also enables people to see through walls. Our work extends the concept of cloaking as a special form of illusion to the wider realm of illusion optics.Comment: Including a paper and its auxiliary materia

Non-closed acoustic cloaking devices enabled by sequential-step linear coordinate transformations

Hitherto acoustic cloaking devices, which conceal objects externally, depend on objects\u27 characteristics. Despite previous works, we design cloaking devices placed adjacent to an arbitrary object and make it invisible without the need to make it enclosed. Applying sequential linear coordinate transformations leads to a non-closed acoustic cloak with homogeneous materials, creating an open invisible region. Firstly, we propose to design a non-closed carpet cloak to conceal objects on a reflecting plane. Numerical simulations verify the cloaking effect, which is completely independent of the geometry and material properties of the hidden object. Moreover, we extend this idea to achieve a directional acoustic cloak with homogeneous materials that can render arbitrary objects in free space invisible to incident radiation. To demonstrate the feasibility of the realization, a non-resonant meta-atom is utilized which dramatically facilitated the physical realization of our design. Due to the simple acoustic constitutive parameters of the presented structures, this work paves the way toward realization of non-closed acoustic devices, which could find applications in airborne sound manipulation and underwater demands

Transformation Plasmonics

This review article provides the state of the art in the emerging topic of transformation plasmonics, with applications thought in cloaking.International audienceSurface plasmons polaritons (SPPs) at metal/dielectric interfaces have raised lots of expectations in the on-going quest towards scaling down optical devices. SPP optics offers a powerful and flexible platform for real two-dimensional integrated optics, capable of supporting both light and electrons. Yet, a full exploitation of the features of SPPs is conditioned by an accurate control of their flow. Most efforts have so far focused on the extrapolation of concepts borrowed from guided optics. This strategy has already led to many important breakthroughs but a fully deterministic control of SPP modes remains a challenge. Recently, the field of optics was stimulated by a novel paradigm, transformation optics, which offers the capability to control light flow in any desired fashion. While it has already significantly contributed to the design of metamaterials with unprecedented optical properties, its versatility offers new opportunities towards a fully deterministic control of SPPs and the design of a new class of plasmonic functionalities. Here, we review recent progress in the application of transformation optics to SPPs. We first briefly describe the theoretical formalism of transformation plasmonics, focusing on its specificities over its three-dimensional optical counterpart. Numerical simulations are then used to illustrate its capability to tame SPP flows at a metal interface patterned with a dielectric load. Finally, we review recent experimental implementations leading to unique SPP functionalities at optical frequencies

Discrete Coordinate Transformation for Designing All-Dielectric Flat Antennas

Transformation electromagnetics provides a practical approach to control electromagnetic fields at will. Based on this principle, novel devices such as the invisible cloak have been proposed. Here we examine the extension of this technique as applied to the design of flat devices in antenna systems. A method using discrete coordinate transformation is proposed, which allows the conversion of conventional devices with curved shapes into flat systems, while preserving their non-dispersive, isotropic, broadband, and lossless properties. Two specific design examples, a flat reflector and a flat lens embedded in free space, are presented. To avoid the loss and narrow bandwidth issues typically present in metamaterials, appropriate approximations and simplifications are introduced to make the all-dielectric devices, which are more practical to build. It is also shown that the discrete coordinate transformation is valid for both the E and H polarizations, as long as the local coordinates of the system remain near-orthogonal. Finite-Difference Time-Domain simulations are used to verify the performances of these designs, and show that the all-dielectric devices have similar broadband performances compared to the conventional ones, while possessing the advantages of flat profiles and small volumes

Transformation elastodynamics and active exterior acoustic cloaking

This chapter consists of three parts. In the first part we recall the elastodynamic equations under coordinate transformations. The idea is to use coordinate transformations to manipulate waves propagating in an elastic material. Then we study the effect of transformations on a mass-spring network model. The transformed networks can be realized with "torque springs", which are introduced here and are springs with a force proportional to the displacement in a direction other than the direction of the spring terminals. Possible homogenizations of the transformed networks are presented, with potential applications to cloaking. In the second and third parts we present cloaking methods that are based on cancelling an incident field using active devices which are exterior to the cloaked region and that do not generate significant fields far away from the devices. In the second part, the exterior cloaking problem for the Laplace equation is reformulated as the problem of polynomial approximation of analytic functions. An explicit solution is given that allows to cloak larger objects at a fixed distance from the cloaking device, compared to previous explicit solutions. In the third part we consider the active exterior cloaking problem for the Helmholtz equation in 3D. Our method uses the Green's formula and an addition theorem for spherical outgoing waves to design devices that mimic the effect of the single and double layer potentials in Green's formula.Comment: Submitted as a chapter for the volume "Acoustic metamaterials: Negative refraction, imaging, lensing and cloaking", Craster and Guenneau ed., Springe

Vibrant times for mechanical metamaterials

Metamaterials are man-made designer matter that obtains its unusual effective properties by structure rather than chemistry. Building upon the success of electromagnetic and acoustic metamaterials, researchers working on mechanical metamaterials strive at obtaining extraordinary or extreme elasticity tensors and mass-density tensors to thereby mold static stress fields or the flow of longitudinal/transverse elastic vibrations in unprecedented ways. In this prospective paper, we focus on recent advances and remaining challenges in this emerging field. Examples are ultralight-weight, negative mass density, negative modulus, pentamode, anisotropic mass density, Origami, nonlinear, bistable, and reprogrammable mechanical metamaterials

Design and implementation of photonic metamaterials

Los metamateriales son una nueva clase de materiales artificiales que pueden ser diseñados para poseer propiedades que serían difíciles o imposibles de encontrar en la naturaleza. Los metamateriales han posibilitado la aparición de un gran número de nuevos dispositivos fotónicos con asombrosas propiedades. Entre ellos, cabe destacar a los medios de índices negativos (NIMs) con los que es posible construir superlentes carentes del límite de resolución de las lentes convencionales, así como los dispositivos basados en óptica de transformación, una nueva teoría del electromagnetismo que permite conocer las propiedades que un medio debe tener para curvar o distorsionar el espacio electromagnético. Como consecuencia, ha sido posible crear dispositivos fascinantes, tales como capas de invisibilidad o agujeros negros ópticos. Debido a su importancia, en esta tesis nos hemos centrado en estas dos aplicaciones de los metamateriales. En el caso de los medios de índice negativo, hemos estudiado cómo éstos pueden ser construidos a partir de estructuras de transmisión extraordinaria. Como resultado principal, se ha diseñado y verificado experimentalmente un novedoso metamaterial de altas prestaciones que presenta una elevada figrua de mérito (sustancialmente mayor que las de trabajos previos)en el espectro visible. La estructura también presenta independencia de polarización y propiedades homogéneas para incidencia normal. Esta demostración corresponde al primer NIM experimental con bajas pérdidas en el régimen visible y también al primero formado por varias celdas unidad en la dirección de propagación, un paso imporante hacia NIMs homogéneos en esta banda. Este trabajo ha sido reconocido como uno de los últimos hitos en metamateriales ópticos tridimensionles. Además, otros autores han demostrado que las propiedades de esta estructura pueden ser empleadas para controlar la velocidad de propagación (subluminal y superluminal) de pulsos laser de femtosengudos o para conseguir cGarcía Meca, C. (2012). Design and implementation of photonic metamaterials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16465Palanci