07/7001 METAMATERIALS FOR SPACE APPLICATIONS

Size: px

Start display at page:

Download "07/7001 METAMATERIALS FOR SPACE APPLICATIONS"

Arnold Cannon
5 years ago
Views:

1 07/7001 METAMATERIALS FOR SPACE APPLICATIONS Type of activity: Medium Study (4 months, 25 KEUR) Background and Motivation Brief description of the Metamaterial concept Metamaterials could be considered as the latest revolution inside of the Electrical and Electronic Engineering community. Indeed, the interest in Metamaterials has given rise to the creation of Metamorphose, an European consortium focus in the scientific research of this new artificial materials. The control over the material properties is traditionally achieved by chemical combination of different compounds in a way that a different substance is obtained. Stainless steel, teflon or kevlar among many others materials are clear success stories of this procedure. If, however, a new material is obtained by a structural combination of different compounds, the resulting structure has its own properties and when considered as a whole, receives the name of composite [1]. The composite materials play nowadays an important role in the different subsystems of a spacecraft, e.g. ceramic matrix composites can be found in the airframe and in the propulsion components. When the composite exhibits new properties in response to an external electromagnetic field, it is referred in the literature as an electromagnetic composite or as a Metamaterial [2]. The properties that Metamaterials are able to show can be as spectacular as: negative permeability and permittivity [3] or an electromagnetic band gap [4]. For a detailed classification of Metamaterials see Ref. [2]. Design of Metamaterial devices Theoretical tools are desirable in the design phase of Metamaterials in order to fully exploit their possibilities, e.g. a left-handed material at visible frequencies has been successfully fabricated by A. N. Grigorenko et al. [5] following theoretical suggestions [6]. For more general purposes a reverse engineering approach is more convenient. However, these kind of approaches are often formulated as an optimization problem, whose solutions are obtained after long computer calculations (see for example Ref. [7]). Recently J. B. Pendry et al. described a coordinate transformation procedure to design an exotic lens capable to cloak objects from electromagnetic radiation [8]. Later this procedure has been formulated in a framework inspired by Einstein's General Theory of Relativity [9,10], whereby the authors exploit the invariance thereof under general coordinate transformations. However, while such transformations in general relativity transform all physical laws and therefore constitute symmetry, this is not true in this application, where the "correct" coordinate system is determined via our independent knowledge of the device. The main advantage of this new strategy lies on its functional character, i.e. given a geometry of the device a spatial distribution of the permittivity,, and permeability,, is directly obtained. In a more detailed work A. Greenleaf et al. reported under which conditions this procedure is valid at all frequencies not only in under the ray approximation but in the full-wave description as well [10]. Once the Metamaterial has been designed, the realization is the next step to be done in the fabrication process. An interesting proposal has been made W. Cai and al. to obtain an electromagnetic cloak [12]. The authors claim that the Metamaterial can be envisaged as a nanostructured material whose averaged spatial distributions of

2 and are the same as the objective ones in the framework of the 'shapedependent' effective-medium theory (EMT) [12,13]. Indeed, the "homogenization" of the Metamaterial permits to describe its response to electromagnetic fields in terms of macroscopic quantities. For the particular fabrication of an invisibility cloak at microwave frequencies D. Shurig et al. made use of split-ring resonators (SRRs) [13] as core elements of the Metamaterial [14]. The later work is considered as the first experimental realization of an invisible device. In Figure (1) we have reproduced the experimental device of Ref. [15] to illustrate the real aspect of a Metamaterial. An interesting collection of design approaches have been recently published by T. A. Leskova et al. [16]. There different approaches are discussed to design a randomly rough surface for a given optical response, e.g. production of scattering fields with specified angular dependencies. Although we only present in this document a reduced number of examples of Metamaterial design strategies many others are reported in the literature. It is relevant to stress out that the control over the properties of a Metamaterial is effectively achieved if good design strategies are available. Space applications of Metamaterial devices The particular properties that characterize Metamaterials have propitiated the appearance of new concept devices, e.g. electromagnetic band gap [4], perfect lenses [17] and invisibility devices [8,18]. These concepts seem to have the potential to play a disruptive role in the development of new devices to be used in space missions: Examples could be in the fields of the design of antennas and waveguides [19], or a photonic bandgap substrate to enhance the performance of a patch-antenna [20]. As further application, the possibility to manipulate electromagnetic fields opens a new way to design lens concepts which are able to expel or concentrate the radiation in a certain space region. The invisibility cloak could have a potential as a thermal isolator. In free space the only mechanism of heat transfer is radiation. Hence, a body inside of the cloaked region became invisible to the incoming radiation and therefore its absorption could be considered negligible. Additionally, an invisibility cloak can reduce the pressure exerted by the solar radiation on a spacecraft, influencing its orbital stability as a result of the particular way in which electromagnetic radiation is scattered by the cloak (as can be inferred from Fig 3 in Ref. [21]). While reliable inverse design strategies are mandatory for any systematic application of Metamaterials, this task becomes much more important and more complicated in space applications. Besides functional specifications essentially defined through the intended purpose of the material, any space application will be faced with numerous additional constraints, such as weight of the device, materials that can be used, robustness and lifetime or workability under extreme conditions. These constraints will reduce the "search space" for Metamaterials with a certain characteristic, which therefore increases the need for sophisticated but reliable inverse engineering methods. At the same time generic inverse design strategies (i.e. strategies not confined to certain applications, realizations or materials) can help to explore all possibilities within the given constraints and therefore offer much more flexibility than design methods restricted to certain situations.

3 Research and Study Objectives As pointed out above, powerful and reliable reverse engineering techniques are indispensable to tap the full potential of Metamaterials in space due to numerous constraints from space environment. The aim of this study is to give an overview of the state of the art in the fields mentioned above and to contribute to investigations particularly important for space applications. The study shall address the following points: 1. Explore the different design approaches in the framework of Metamaterials, whereby particular emphasis should be put on those exhibiting a functional character similar to the aforementioned coordinate transformation developed by J. B. Pendry et al. [4]. 2. The most fundamental parameters that define the behaviour of a Metamaterial are, μ, and the geometry of the interfaces. The first task to be accomplished in this point is to explore which are the main variables that can affect the above mentioned fundamental parameters, e.g. the electromagnetic frequency of the incident radiation, radiation power, the temperature of the system, structural strain, etc. Among them the most critical ones with respect to relative changes should be identified. Then, one design strategy described in point 1 should be chosen for studying the impact of the identified critical variables over the final design of the Metamaterial. After the completion of points 1 and 2, the study should have covered the fundamentals on the design of real Metamaterials. One additional problem should be addressed in the study. The following points can serve as an example, although original proposals from Universities are highly welcome: 3. The coordinate transformation technique can be formulated within General Theory of Relativity. Until now the analogy has been used only in a static situation; electromagnetic waves behave as test particles on a fixed background. The dynamical equations (Einstein equations) have not been used. It seems that in any GR formulation the electromagnetic field itself should not enter the dynamical equations of space-time: while in GR, electromagnetic fields are sources for space-time curvature, this clearly is not the case for Metamaterials. Still, it could be interesting to see if and how it is possible to relate time dependent coordinate transformations to dynamical perturbations of space-time. This should result in dynamical laws for spacetime itself, which of course need not be equivalent to Einsteins equations. Still, this could help to understand time-dependent changes due to the change of the environment, i.e. serve in some applications as a way to tackle the impact of some critical variables as described point Changing the characteristics of parts of a spacecraft without mechanical operations is particularly interesting in space. Therefore, Metamaterials that present a bistable response to electromagnetic radiation are of interest. In the same way as a ferroelectric material changes its internal polarization after applying a given external electric field, the bistable Metamaterial should change its optical properties after applying an external perturbation. This external perturbation could be an external electric/magnetic field or a perturbation of different nature. The study aims at proposing and exploring

4 possible techniques to design materials of this kind and further integrating them (depending on their nature) into reverse engineering models. To summarize: A successful proposal need to cover the points 1 and 2, and a selection from 3 and 4, or an original study point. References [1] K. K. Chawla, Composite Materials: Science and Engineering, Springer (1998) [2] A. Sihvola, Metamaterials in electromagnetics, Metamaterials 1, 2 (2007) [3] D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser and S. Schultz, Composite medium with simultaneously negative permeability and permittivity, Phys. Rev. Lett. 84, 4184 (2000) [4] M. Notomi, Theory of light propagation in strongly modulated photonic crystals: refraction like behaviour in the vicinity of the photonic band gap, Phys. Rev. B 62, (2000) [5] A. N. Grigorenko, Nanofabricated media with negative permeability at visible frequencies, Nature 483, 335 (2005) [6] L. V. Panina, A. N. Grigorenko, and D. P. Makhnovskiy, Metal-dielectric medium with conducting nanoelements, Phys. Rev. B 66, (2002); V. A. Podolskiy, A. K. Sarychev, and V. M. Shalaev, Plasmon modes in metal nanowires and left-handed materials, J. Nonlinear Opt. Phys. Mater. 11, 65 (2002) [7] P. Ben-Abdallah, Microstructured Radiators, European Space Agency, the Advanced Concepts Team, Ariadna Final Report (2007) [8] J. B. Pendry, D. Shurig, and D. R. Smith, Controlling electromagnetic fields, Science 312, 1780 (2006) [9] D. Schurig, J. B. Pendry, and D. R. Smith, Calculation of material properties and ray tracing in transformation media, Opt. Express 8, 655 (2001) [10] U. Leonhardt and T. G. Philbin, General relativity in electrical engineering, New J. Phys. 8, 247 (2006) [11] A. Greenleaf, Y. Kurylev, M. Lassas, and G. Uhlmann Full-wave invisibility of active devices at all frequencies, arxiv:math.ap/ (2007) [12] W. Cai, U. K. Chettiar, A. V. Kildishev and V. M. Shalaev, Optical cloacking with metamaterials, Nature Photonics 1, 224 (2007) [13] V. M. Shalaev, Nonlinear Optics of Random Media: Fractal Composites and Metal- Dielectric Films, Springer (2000) [14] J. B. Pendry, A. J. Holden, D. J. Roberts, and W. J. Stewart, Magnetism from conductors and enhanced nonlinear phenomena, IEEE Trans. Micr. Theory Techniques 47, 2075 (1999) [15] D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, and D. R. Smith1, Metamaterial electromagnetic cloak at microwave frequencies, Science 314, 977 (2006) [16] T. A. Leskova, A. A. Maradudin, E. E. García-Guerrero, E. R. Méndez, Structured surfaces as optical metamaterials, Metamaterials 1, 19 (2007) [17] J. B. Pendry, Negative refraction makes a perfect lens, Phys. Rev. Lett. 85, 3966 (2000)

5 [18] U. Leonhardt, Optical conformal mapping, Science 312, 1777 (2006) [19] N. Engheta and R. W. Ziolkowski, Metamaterials: Physics and Engineering Explorations, Wiley-IEEE Press (2006) [20] R. Gonzalo, P. de Maagt, and M. Sorolla, Enhanced patch-antenna performance by suppressing surface waves using photonic-bandgap substrates, IEEE Transactions on MTT 47, 2131 (1999) [21] S. A. Cummer, B.-I. Popa, D. Schurig, D. R. Smith, and J. B. Pendry, Full-wave simulations of electromagnetic cloaking structures, Phys. Rev. E 74, (2006)

New Concept Conformal Antennas Utilizing Metamaterial and Transformation Optics

New Concept Conformal Antennas Utilizing Metamaterial and Transformation Optics The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation