SCANNING THE ISSUE Metamaterials: Fundamentals and Applications in the MicrowaveandOpticalRegimes By GEORGE V. ELEFTHERIADES, Fellow IEEE Guest Editor

NADER ENGHETA, Fellow IEEE Guest Editor

etamaterials are artificially structured media with unusual Typically, metamaterials are peri- electromagnetic properties ranging from radio frequency odic structures consisting of subwave- and microwaves all the way up to optical frequencies. In its length metalo-dielectric scatterers modern form, the field of Bmetamaterials,[ which has its having a periodicity that is much Mroots in the history of artificial dielectrics, is just over ten years old but has already smaller than the impinging and guided attracted strong interest from many researchers around the globe. Suddenly, wavelengths (although nonperiodic classical electromagnetism took on a metamaterials are also entirely possi- fresh and exciting perspective reveal- ble). These constituent scatterers or ing that there are fascinating phenom- Binclusions[ behave like Bartificial ena still awaiting to be discovered and This Special Issue on molecules[ that scatter an incident corresponding applications to be in- Metamaterials: Artificially electromagnetic wave giving rise to vented. In particular, all this richness is macroscopic effective material param- associated with the notion of the Engineered Materials with eters such as a permittivity, a perme- macroscopic constitutive parameters Electromagnetic ability, and a refractive index. Although such as the permittivity and perme- Properties covers topics the term Bmetamaterial[ is relatively ability. What would be possible if we on prescribing material new, a precursor concept dates back to were able to synthesize materials with parameters to obtain the late part of the nineteenth century user-defined constitutive parameters? exotic new functions, in the work of Jadagis Chunder Bose on The richness of these possibilities the rotation of the plane of polarization becomes more evident when we recall physically implementing by his man-made twisted structures, the fact that material parameters can in metamaterials, and resembling chiral structures [1]. In general be anisotropic tensors which applying them in the 1914, Karl Ferdinand Lindman investi- can also be spatially inhomogeneous microwave and optical gated artificially engineered chiral (varying from point to point). More- domains. media, which he constructed by a over, they can attain values previously collection of wire helices [2]. This not considered, and they can even mix was followed by a few other researchers together the electric and magnetic response of a material. This Special Issue in the first half of the twentieth century contains 16 papers written by some of the internationally renowned leaders in the studying some other man-made mate- field who discuss how to prescribe material parameters to obtain exotic new rials. In the late 1940s, 1950s, and functions, how to physically implement such metamaterials, and how to apply 1960s, Bartificial dielectrics[ became a them in the microwaves and optical domains. subject of interest, when Winston E. Kock of the Bell telephone laboratories Digital Object Identifier: 10.1109/JPROC.2011.2161808 developed this concept in order to

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realize lightweight lenses at microwave Veselago in 1967 [6], the intriguing split-ring resonators. The paper makes frequencies (in the 3Y5-GHz range), and groundbreaking notion of the use of a rigorous homogenization where the wavelength is long (several Bperfect lens[ proposed by Pendry in treatment of these metamaterials. centimeters) and thus the correspond- 2000 [14], and the experimental ver- Moreover, an exciting application of ing natural dielectric lenses are bulky ification of the negative-index meta- such magnetic metamaterials is de- and heavy [3]. The corresponding materials in the microwave regime by scribed for enhancing the resolution Bartificial molecules[ were electrically Shelby, Smith, and Schultz in 2001 [9] of surface coils in magnetic resonance small metallic disks periodically ar- stimulated interest in these materials imaging (MRI). The paper by Alu` and ranged in a lens shape. The interest in and led to the expansion and growth in Engheta describes the possible idea for artificial complex materials, particular- this field in the 2000s. The field of realization of metamaterials in the ly chiral materials, was resurrected in metamaterials has now reached a optical regime based on lumped optical the 1980s and 1990s, mostly with the variety of disciplines such as physics, nanocircuit element concepts. The view towards applications in micro- electrical engineering, material science, paper establishes a way to realize wave radar absorbing materials and mathematics, mechanics, acoustics, nanocapacitors and nanoinductors us- other microwave devices and compo- fluidics, and chemistry just to name ing dielectric and plasmonic nanopar- nents [4]. A comprehensive review of a few. ticles. It also presents a method of artificial dielectrics, including a rigor- The first paper in this Special combining these elements to synthe- ous mathematical treatment, from that Issue is by Kundtz, Smith, and Pendry size complex optical nanocircuits by era can be found in [5]. who introduce and review the notion treating the displacement current using In the present context, metama- of Btransformation optics[ (TO) as a well-known low-frequency circuit terials can be defined as artificially powerful technique for designing theory techniques. Finally, the paper engineered materials with electro- electromagnetic metamaterials based establishes a method for designing 0-D, magnetic properties that are inacces- on the invariance of Maxwell’s equa- 1-D, 2-D, and 3-D optical metamaterial sibleinnatureoraredifficultto tions. Specifically, at the heart of TO structures based on transmission-line obtain in natural materials, but are lies the use of coordinate transforma- concepts thus helping to decrease physically realizable. One of the early tions which can be translated to losses and improve bandwidth. The examples of metamaterials is the material parameters. In this way, following paper by Valentine, Zhang, so-called Bnegative-index,[Bleft- several novel electromagnetic device Zentgraf, and Zhang presents the so- handed[ or Bdouble negative[ meta- examples are introduced and dis- called cascaded Bfishnet[ structures for material which is characterized by cussed including cloaks, beam shif- building broadband low-loss negative- simultaneously negative permittivity ters, and beam splitters. refraction metamaterials. It deals with and permeability, thus implying a The following paper by Zedler and design, fabrication, and characteriza- negative index of refraction. These Eleftheriades introduces a method for tion of such materials. The paper shows media were theoretically suggested synthesizing TO metamaterials at how coupling of unit cells leads to and studied by Victor Veselago in the microwaves (hence more appropriate- lower loss and a high figure of merit. 1960s [6]. Inspired by the work of ly Btransformation electromagnetics[) Kildishev, Borneman, Shalaev, and Pendry [7], [8], Shelby, Smith, and using loaded transmission lines. These Drachev in their paper give an overview Schultz experimentally demonstrated metamaterials are in general inhomo- of some principles in the development the first left-handed metamaterial in geneous and anisotropic with nonzero of bianisotropic homogenization tech- 2001 using arrays of wires (giving rise off-diagonal material parameters. A niques for metamaterials, and provide to negative permittivity) and split-ring few examples of microwave devices examples in passive and active optical resonators (giving rise to negative per- are described including broadband metamaterials. meability) at microwave frequencies cloaks and flattened retroreflectors. The next group of six papers [9]. In the electrical engineering com- The next paper by Alitalo and describes specific applications of munity, a different realization ap- Tretyakov describes an alternative metamaterials at microwave and opti- proach has also been considered at approach for cloaking based on trans- cal frequencies. The paper by Dura´n- microwaves using 2-D loaded networks mission-line metamaterials, and also Sindreu, Ve´lez, Siso´,Ve´lez, Selga, of transmission lines [10], [11], which gives a brief overview of some other Bonache, and Martin reviews recent were subsequently extended to the cloaking techniques. advances in metamaterial transmission optical regime [12]. Typically this The next four papers deal with lines based on loading with split-ring transmission-line approach leads to specific ideas for realizations of meta- resonators. The paper highlights the reduced transmission losses and wide materials with user-defined param- advantages of transmission-line meta- bandwidths due to the tight coupling eters. The paper by Marque´s, Jelinek, materials and describes a number of of the constituent unit cells [13]. The Freire, Baena, and Lapine discusses the enabled microwave applications. Such pioneering work on the concept of realization of 3-D magnetic metamater- applications include compact wideband negative-index metamaterials by ials at microwave frequencies using filters and power splitters. Caloz in his

Vol. 99, No. 10, October 2011 | Proceedings of the IEEE 1619 Scanning the Issue

paper reviews the theory and advan- discussed by Lam, Vier, Nielsen, describes some interesting and useful tages of transmission-line metamater- Parazzoli, and Tanielian. This applica- pattern surfaces (near-field plates) ials with particular emphasis on their tion, however, concerns phased arrays that can focus microwaves down to frequency dispersion properties. Based as applied, for example, to the case of subwavelength spots. Both 1-D and on dispersion analysis, the author satellite communications. The paper 2-D plates are described as well as describes a number of interesting introduces an interesting metamaterial their applications to imaging, sensing, Bdispersion engineering[ microwave lens structure that is designed using and wireless power transfer. applications including a pulse-position transformation optics. This lens extends The field of metamaterials has modulator and a real-time spectrum the scanning capability of phased arrays expanded so vastly that it is impossible analyzer using leaky-wave antennas. to directions close to the horizon which to represent all its subfields and topics The paper concludes by introducing is a Bclassical[ challenge in conven- of research in one special issue. As a some interesting microwave nonrecip- tional phased-array antennas. result, the present collection of papers rocal magnetic devices using ferro- The next three papers deal with in this issue is by no means exhaustive. magnetic nanowires. The papers by some special problems and applica- Multivolume handbooks would be ne- Ziolkowski, Jin, and Lin, and by Volakis tions of structures that strictly speak- cessary to include all the various areas and Sertel review several interesting ing are not metamaterials but are of this field. We refer the interested and useful applications of metamata- closely related to them. The paper by readerstonumerousotherspecial materials in electrically small antennas. Notomi describes methods for strong issues of various technical journals, The paper by Ziolkowski, Jin, and Lin light confinement in dielectric pho- books, and monographs on metama- focuses on the realization of electrically tonic crystals. Ultrahigh-Q cavities terials in the fields of engineering, small but efficient antennas using with the quality factor on the order physics, material science, chemistry, metamaterial loading. Multiband and of 106 and higher are described which and mathematics among others. The multifrequency antennas are also dis- are capable of confining light in a metamaterial research is vibrant, pro- cussed. The paper by Volakis and Sertel wavelength-cubed volume. It is shown gressing steadily and strongly into describes electrical small antennas that such structures can have applica- various exciting forefronts which in- based on unique anisotropic metama- tions in low-power, integrated pho- clude quantum metamaterials, super- terial structures. The paper concludes tonic circuits and photonic network- conducting metamaterials, tunable by describing remarkable wideband on-chips, in developing extremely and reconfigurable metamaterials, arrays based on metamaterial ideas and slow light systems, and in adiabatic photonic metamaterials, infra-red me- the concept of the Bcurrent sheet.[ The tuning of light. The following paper by tamaterials, and terahetz metamater- paper by Hashemi and Itoh reviews Jackson, Burghignoli, Lovat, Capolino, ials,justtonameafew.Sothefuture the application of transmission-line Chen, Wilton, and Oliner tackles the of this field is quite bright. metamaterials in the realization of important problem of directive beam- We wish to thank the authors for leaky-wave antennas. Such leaky-wave ing through periodic structures at their outstanding contributions and the antennas exhibit unique beam scanning microwave and optical frequencies. reviewers whose careful reviews led to properties that can continuously scan Theunderlyingmechanismisidenti- the improvement of the quality of the from backward end fire to forward end fied as the involvement of weakly papers. We would also like to express fire and even scan through broadside. attenuated leaky waves. The paper our appreciation to J. Calder, Managing The paper presents electronically scan- discusses the role of these leaky waves Editor, and J. Sun, Publications Editor, nable, conformal, and dual polarization in the near field of the aperture and of the Proceedings of the IEEE, for leaky-wave antennas. Another applica- the far field of the structures. Finally, their help and support throughout the tion of metamaterials to antennas is the last paper by Grbic and Merlin preparation of this Special Issue. h

REFERENCES [5] R. E. Collin, Field Theory of Guided Waves. index of refraction,[ Science, vol. 292, Y B Piscataway, NJ: IEEE Press, 1990, ch. 12. pp. 77 79, Apr. 6, 2001. [1]J.C.Bose, On the rotation of plane B of polarisation of electric waves by a [6]V.G.Veselago, The electrodynamics of [10] G. V. Eleftheriades, A. K. Iyer, and substances with simultaneously negative P. C. Kremer, BPlanar negative refractive twisted structure. Proc. Roy. Soc., vol. 63, " [ pp. 146Y152, 1898. values of and , Sov. Phys. Usp.,vol.10, index media using periodically L-C loaded pp. 509Y514, Jan.YFeb. 1968. transmission lines,[ IEEE Trans. Microw. [2] I. V. Lindell, A. H. Sihvola, and J. Kurkijarvi, Theory Tech., vol.50,no.12,pp.2702Y2712, BKarl F. Lindman: The last Hertzian, and [7] J.B.Pendry,A.J.Holden,D.J.Robbins,and [ W. J. Stewart, BMagnetism from conductors Dec. 2002. a Harbinger of electromagnetic chirality, [ B IEEE Antennas Propag. Mag., vol. 34, no. 3, and enhanced nonlinear phenomena, [11]A.Sanada,C.Caloz,andT.Itoh, Planar Y IEEE Trans. Microw. Theory Tech., vol. 47, distributed structures with negative pp. 24 30,Jun.1992. Y [ B [ no. 11, pp. 2075 2081, Nov. 1999. refractive index, IEEE Trans. Microw. [3] W. Kock, Metallic delay lenses, Bell Syst. Theory Tech., vol. 52, no. 4, pp. 1252Y1263, Tech. J., vol. 27, pp. 58Y82, 1948. [8]J.B.Pendry,A.J.Holden,D.J.Robbins,and W. J. Stewart, BLow-frequency plasmons in Apr. 2004. [4]N.Engheta,Ed.BSpecial Issue on ‘Wave [ B [ thin wire structures, J. Phys., Condensed [12] A. Alu and N. Engheta, Three-dimensional interaction with chiral and complex media’, Matter., vol. 10, pp. 4785Y4809, 1998. nanotransmission lines at optical J. Electromagn. Waves Appl., vol. 6, no. 5/6, [9] R. A. Shelby, D. R. Smith, and S. Schultz, frequencies: A recipe for broadband May/Jun. 1992. [ BExperimental verification of a negative negative-refraction optical metamaterials, Phys. Rev. B., vol.75,Jan.2007,024304.

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[13] G. V. Eleftheriades, BAnalysis of bandwidth coupled resonators,[ IEEE Microw. Wireless [14] J. B. Pendry, BNegative refraction makes and loss in negative-refractive-index Compon. Lett., vol. 17, no. 6, pp. 412Y414, aperfectlens,[ Phys. Rev. Lett., vol. 85, transmission-line (NRI-TL) media using Jun. 2007. pp. 3966Y3969, Oct. 2000.

ABOUTTHEGUESTEDITORS George V. Eleftheriades (Fellow, IEEE) received whereheiscurrentlytheRamseyProfessor.Heisalsoamemberofthe the diploma in electrical engineering from the Mahoney Institute of Neurological Sciences. He was the graduate group National Technical University of Athens, Athens, chair of electrical engineering from July 1993 to June 1997. His current Greece, in 1988 and the M.S.E.E. and Ph.D. degrees research interests and activities span over a broad range of areas in electrical engineering from the University of including metamaterials and plasmonics, nano-optics and nanopho- Michigan, Ann Arbor, in 1989 and 1993, respectively. tonics, nanocircuits and nanostructures modeling, bio-inspired/biomi- From 1994 to 1997, he was with the Swiss metic polarization imaging and reverse engineering of polarization Federal Institute of Technology, Lausanne, vision, miniaturized antennas and nanoantennas, hyperspectral sensing, Switzerland. Currently, he is a Professor in the biologically based visualization and physics of sensing and display of Department of Electrical and Computer Engineer- polarization imagery, through-wall microwave imaging, fields and waves ing, University of Toronto, Toronto, ON, Canada, where he holds the phenomena, fractional operators, and fractional paradigm in electrody- Canada Research Chair/Velma M. Rogers Graham Chair in Engineering. He namics. He has published numerous journal papers, book chapters, and is one of the originators of the field of transmission-line metamaterials conference articles in his fields of research. He coedited (with R. W. which he introduced in 2002. Along with his graduate students he Ziolkowski) the book Metamaterials: Physics and Engineering Explora- produced the first experimental evidence of imaging beyond the tions (New York: Wiley/IEEE Press, 2006). diffraction limit with a negative-index lens and invented a number of Dr. Engheta was selected as one of the Scientific American Magazine novel metamaterial-based microwave devices and antennas. Some of this 50 Leaders in Science and Technology in 2006 for developing the work has been compiled in the book Negative-Refraction Metamaterials: concept of optical lumped nanocircuits. He is a Guggenheim Fellow, an Fundamental Principles and Applications (New York: Wiley/IEEE Press, IEEE Third Millennium Medalist, a Fellow of the American Physical June 2005, G. V. Eleftheriades and K. G. Balmain, Eds.). His research Society (APS), the Optical Society of America (OSA), the American interests include transmission-line and other electromagnetic metama- Association for the Advancement of Science (AAAS), and the SPIEVThe terials, small antennas and components for wireless communications, International Society for Optical Engineering. He is the recipient of the passive and active microwave components, near-field imaging techni- 2008 George H. Heilmeier Award for Excellence in Research from UPenn, ques, plasmonic and nanoscale optical structures, fundamental the Fulbright Naples Chair Award, NSF Presidential Young Investigator electromagnetic theory, and electromagnetic design of high-speed award, the UPS Foundation Distinguished Educator term Chair, and interconnects. several teaching awards including the Christian F. and Mary R. Lindback Prof. Eleftheriades has served as an IEEE Antennas and Propagation Foundation Award, the W. M. Keck Foundation’s 1995 Engineering Society (APS) Distinguished Lecturer (2004Y2009) and as a member of Teaching Excellence Award, and two times recipient of S. Reid Warren, the IEEE APS Administrative Committee (AdCom, 2008Y2010). He is an Jr. Award. He has been selected to receive the 2012 IEEE Electromag- associate editor of the IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION netics Award for his contributions to the fields of metamaterials and and a member of Technical Coordination Committee Microwave Field nanoscale optics. He was an Associate Editor of the IEEE ANTENNAS AND Theory (MTT-15). He has been the General Chair of the 2010 IEEE WIRELESS PROPAGATION LETTERS (2002Y2007), the IEEE TRANSACTIONS ON International Symposium on Antennas and Propagation and CNC/USNC/ ANTENNA AND PROPAGATION (1996Y2001), and Radio Science (1991Y1996). URSI Radio Science Meeting held in Toronto, ON, Canada. He was the He was on the Editorial Board of the Journal of Electromagnetic Waves recipient of the 2008 IEEE Kiyo Tomiyasu Technical Field Award Bfor and Applications. He is currently on the Editorial Board of Metamaterials, pioneering contributions to the science and technological applications of on the board of Waves in Random and Complex Media,andonthe negative-refraction electromagnetic materials.[ He was the recipient of Editorial Board of the Istituto Superiore Mario Boella Book Series in the 2001 Ontario Premiers’ Research Excellence Award and the 2001 Radio Science.HeservedasanIEEEAntennasandPropagationSociety Gordon Slemon Award presented by the University of Toronto. He was Distinguished Lecturer for 1997Y1999. He is a member of Sigma Xi, also the recipient of the 2004 E.W.R. Steacie Fellowship presented by the Commissions B, D, and K of the U.S. National Committee (USNC) of the Natural Sciences and Engineering Research Council of Canada. He is the International Union of Radio Science (URSI), and a member of the corecipient (with L. Markley) of the inaugural 2009 IEEE Microwave and Electromagnetics Academy. He is the Chair of the Commission B of USNC- Wireless Components Letters Best Paper Award. One of his papers (with URSI for 2009Y2011. He is the Chair of the Gordon Research Conference A. Iyer) received the RWP King Best Paper Award in 2008. In 2009, he on Plasmonics in 2012. He has organized and chaired various special has been elected a Fellow of the Royal Society of Canada. sessions in international symposia and conferences, and has guest edited/coedited several special issues, namely, the special issue of the Nader Engheta (Fellow, IEEE) received the B.S. Journal of Electromagnetic Waves and Applications on the topic of BWave degree in electrical engineering from the Univer- interaction with chiral and complex media[ in 1992, part special issue of sity of Tehran, Tehran, Iran, in 1978 and the M.S. the Journal of the Franklin Institute on the topic of BAntennas and and Ph.D. degrees in electrical engineering from microwaves[ (from the 13th Annual Benjamin Franklin Symposium) in the California Institute of Technology (Caltech), 1995, special issue of the Wave Motion on the topic of BElectrodynamics Pasadena, in 1979 and 1982, respectively. in complex environments[ (with L. B. Felsen) in 2001, special issue of the He is the H. Nedwill Ramsey Professor of IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION on the topic of Electrical and Systems Engineering, and Professor BMetamaterials[ (with R. W. Ziolkowski) in 2003, special issue of Solid of Bioengineering at the University of Pennsylva- State Communications on the topic of BNegative refraction and nia, Philadelphia. After spending one year as a metamaterials for optical science and engineering[ (with G. Shvets) in postdoctoral research fellow at Caltech and four years as a Senior 2008, and the special issue of the IEEE JOURNAL OF SELECTED TOPICS IN Research Scientist as Kaman Sciences Corporation’s Dikewood Division in QUANTUM ELECTRONICS on the topic of BMetamaterials[ (with V. Shalaev, Santa Monica, CA, he joined the faculty of the University of Pennsylvania, N. Litchinitser, R. McPhedran, E. Shamonina, and T. Klar) in 2010.

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