Home Search Collections Journals About Contact us My IOPscience Pioneers in metamaterials: John Pendry and Victor Veselago This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 J. Opt. 13 020401 (http://iopscience.iop.org/2040-8986/13/2/020401) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 193.232.212.153 The article was downloaded on 09/12/2010 at 10:39 Please note that terms and conditions apply. IOP PUBLISHING JOURNAL OF OPTICS J. Opt. 13 (2011) 020401 (6pp) doi:10.1088/2040-8978/13/2/020401 COMMUNITY PERSPECTIVE Pioneers in metamaterials: John Pendry and Victor Veselago Allan Boardman1 Joule Physics Laboratory, University of Salford, Greater Manchester, M5 4WT, UK Received 6 September 2010, accepted for publication 18 October 2010 Published 1 December 2010 Online at stacks.iop.org/JOpt/13/020401 Abstract This article is a tribute designed to praise two great scientists who have set the world alight by stimulating boundless curiosity about metamaterials. It is stated early on that it is not intended to be a technical review but one from which it is possible to understand what the excitement is about. To achieve this outcome some simple discussions of refractive index are used as a means of getting to the now famous concept of negative index. After some selective, quasi-historical, development, the article moves on to a specific section about the pioneers themselves. It presents some impressions of their backgrounds, including the fact that John Pendry is now known now as Sir John Pendry. This flows from the recognition of his work by Queen Elizabeth. It is acknowledged that Victor Veselago truly guided the world along the track of negative refraction with a remarkable display of prescience. It is asserted that metamaterials have a brilliant future and that very important work is progressing towards the production of loss-free and active negative index and other forms of metamaterials. It pointed out that the control of light paths through the distortion of space is currently a major outcome from the groundbreaking work of the pioneers and that, in fact, light concentrators and optical black holes may well be life-transforming consequences. Indeed, in the conclusion, it is stated, unreservedly, that the whole world is indebted to John Pendry and Victor Veselago. Keywords: metamaterials, negative refraction, cloaking, pioneers 1. Introduction by the idea of embracing negative refractive index materials, some aspects of which will be outlined below. The ignition This article is designed to praise two very important people, point occurred at a much earlier time than the last decade, who have stimulated so much activity in the fascinating however, through the seminal negative index work of Victor area of metamaterials. It is not to be a technical review Veselago [2]. To this has been added the groundbreaking work but something that is more widely accessible. It contains of John Pendry [3] that magnificently stoked the fires of both just enough information, however, to enable a comfortable curiosity- and application-driven search for negative refractive impression to be constructed of what precisely these two great index media at the turn of the new millennium. The world scientists have done for the world, in terms of creating a lot truly became ignited and enthused by the pivotal experimental of excitement and focused action. The wonderful modern observation of this type of refraction [4]. poet Mary Oliver [1], in her poem ‘What I have learned In order to access the early concepts emanating from the so far’, asks us to recognize that ‘All summations have a work of Pendry and Veselago some elementary points will now beginning, all effect has a story, all kindness begins with the be made. The first everyday observation is that substances, sown seed. Thought buds towards radiance. Be ignited, or be in various forms, refract at optical frequencies. This is well- gone’. In a very potent way, metamaterials ignited the world known to everybody, without having to be a scientist. Indeed, it at the beginning of the last decade, and the flame was fanned is not necessary to embrace optics as a discipline to appreciate 1 Journal of Optics, Topical Editor, Metamaterials and Structured Photonic that lenses seem to work as they are expected to, and that Materials. rainbows can appear in the sky [5]. The common view would 2040-8978/11/020401+06$33.00 1 © 2011 IOP Publishing Ltd Printed in the UK & the USA J. Opt. 13 (2011) 020401 Community Perspective John Pendry Victor Veselago be that this is all about the magnitude of something called the with apparently ordinary materials, taking the positive sign is refractive index, which is the measure of how much light slows a natural, and apparently obvious, choice. Secondly, it can be down when passing from a medium like air into glass, for imagined that both the dielectric permittivity and the magnetic example. It is customary to set the sign of this index to be permeability could be negative, if only such a material could be positive and associate it with transparent materials. The use found. If that is the case, then, perhaps, the conclusion is that of an index to divide into the speed of light in an unbounded such a double negative isotropic medium is best described by a material to get a smaller value than it has in a vacuum lies negative index. These basic aspects developed into a vigorous at the heart of the familiar Snell’s law, which preceded the discussion and it soon became clear that the history of negative publication of Maxwell’s equations by over 200 years. The refraction goes back a long way [6], if uniaxial (anisotropic) idea of attributing a negative refractive index to materials like materials like calcite are used, for example. However, the glass, or water droplets in the sky, seems to be unnecessary real point is this. Nobody took any notice, until the last and, indeed, perverse. Assigning a positive value is enough decade started to unfold, awakened the world and caused it and is apparent common sense. This argument holds up to ask some really penetrating questions about what it felt it nicely, without the use of Maxwell’s equations, when it is already knew so well. All of these comments paint a picture of believed that optical magnetism is not a feature of what is an important feature of the scenario created by the Pendry– being examined, when referring to ordinary, isotropic, glass Veselago revolution that swept all before it with the tide of windows, or rainbows. However, it can be guessed, quite breathtaking metamaterial research in the last decade. reasonably, that if such materials did naturally, or unnaturally, But, why introduce the word metamaterial? This possess both dielectric and magnetic properties then it may is another aspect of the story of the Pendry–Veselago be necessary to think again about the sign of the refractive revolutionary decade, and the invention of the word is index. The main thought would be that maybe it is possible attributed to Walser [7], who celebrated the new millennium to discover, or manufacture, isotropic materials with a negative by introducing the name metamaterials for a description of index, if only the scientific community could be sufficiently the effective behaviour of composites, about which a little imaginative. A starting point is to deconstruct the meaning more will be said later. In spite of this attractive terminology of the refractive index of a material and recognize that this is for a new range of composites, the highly visible driver of a derived concept that was being used in science long before global news and excitement, as stated earlier, actually was the Maxwell’s equations appeared on the scene. Even after their wonderful idea of negative refraction in isotropic materials. arrival, refractive index did not emerge naturally from them. Nevertheless, underpinning this excitement was, indeed, the In fact, the refractive index is the square root of the product need for composites, or metamaterials, in this area to act as of the relative dielectric permittivity and the relative magnetic demonstrators [3, 4]. This became more and more urgent and permeability of a material. This raises two interesting points. inspirational, not only to scientists but to the media as well. First, in taking a square root, mathematically, it has to be Regardless of how many tracks can be made back into admitted that two signs are always on offer but, when dealing the early part of the last century, the world accepts proudly 2 J. Opt. 13 (2011) 020401 Community Perspective that the ignition point was the pioneering 1968 paper [2] called the plasma, or plasmon, frequency [10] and this is very by Veselago on the electrodynamics of isotropic substances high, beyond the familiar visible frequency window. The with simultaneously negative values of dielectric constant and net result at lower electromagnetic frequencies, even in the magnetic permeability. Within this beautiful work, Veselago optical range, is that the electrons will oppose transmission categorically stated that there had not been, so far, any by creating an imaginary index and there will be an effective experiment in which a substance such as this could even be negative relative permittivity. This is often called plasmon identified. He went on to discuss how to look for such behaviour. On the other hand, a metal ring with a piece cut materials, the impact upon the Doppler effect and the creation out of it (a split-ring) has a classical response to an incoming of special lenses based upon negative refraction.