Editing Metamaterial (section)

==History==
{{main|History of metamaterials}}
Explorations of artificial materials for manipulating [[electromagnetic wave]]s began at the end of the 19th century. Some of the earliest structures that may be considered metamaterials were studied by [[Jagadish Chandra Bose]], who in 1898 researched substances with [[chiral]] properties. Karl Ferdinand Lindman studied [[Dispersion (optics)|wave interaction]] with metallic [[helices]] as artificial [[Chirality (chemistry)|chiral media]] in the early twentieth century.

In the late 1940s, [[Winston E. Kock]] from [[AT&T Bell Laboratories]] developed materials that had similar characteristics to metamaterials. In the 1950s and 1960s, artificial [[dielectric]]s were studied for lightweight [[microwave antenna]]s. Microwave [[Radar-absorbent material|radar absorbers]] were researched in the 1980s and 1990s as applications for artificial chiral media.<ref name=metamaterialplasmonics1/><ref>{{cite journal |title=Birefringent left-handed metamaterials and perfect lenses for vectorial fields |journal=New Journal of Physics |date=2005 |volume=7 |issue=1 |page=220 |doi=10.1088/1367-2630/7/1/220|arxiv=physics/0412128 |doi-access=free |bibcode=2005NJPh....7..220Z |last1=Zharov |first1=Alexander A. |last2=Zharova |first2=Nina A. |last3=Noskov |first3=Roman E. |last4=Shadrivov |first4=Ilya V. |last5=Kivshar |first5=Yuri S. }}</ref><ref>Bowers J. A.; Hyde R. A. et al. "Evanescent electromagnetic wave conversion lenses I, II, III" US Patent and Trademark Office, Grant US-9081202-B2, 14 juli 2015, {{US Patent|9081202}}</ref>

Negative-index materials were first described theoretically by [[Victor Veselago]] in 1967.<ref name=slyusarmeta>{{cite conference|last =Slyusar |first=V.I.|title= Metamaterials on antenna solutions|conference =7th International Conference on Antenna Theory and Techniques ICATT’09 |location =Lviv, Ukraine|date = October 6–9, 2009|pages= 19–24 |url = http://www.slyusar.kiev.ua/019_024_ICATT_2009.pdf}}</ref> He proved that such materials could [[transparency (optics)|transmit light]]. He showed that the [[phase velocity]] could be made anti-parallel to the direction of [[Poynting vector]]. This is contrary to [[wave propagation]] in naturally occurring materials.<ref name="Veselago1" />

In 1995, John M. Guerra fabricated a sub-wavelength transparent grating (later called a photonic metamaterial)  having 50&nbsp;nm lines and spaces, and then coupled it with a standard oil immersion microscope objective (the combination later called a super-lens) to resolve a grating in a silicon wafer also having 50&nbsp;nm lines and spaces. This super-resolved image was achieved with illumination having a wavelength of 650&nbsp;nm in air.<ref name="Guerra 3555–3557"/>

In 2000, [[John Pendry]] was the first to identify a practical way to make a left-handed metamaterial, a material in which the [[right-hand rule]] is not followed.<ref name="slyusarmeta" /> Such a material allows an electromagnetic wave to convey energy (have a [[group velocity]]) against its [[phase velocity]]. Pendry hypothesized that metallic wires aligned along the direction of a wave could provide negative [[permittivity]] ([[dielectric function]] ε < 0). Natural materials (such as [[ferroelectricity|ferroelectrics]]) display negative permittivity; the challenge was achieving negative permeability (μ < 0). In 1999, Pendry demonstrated that a split ring (C shape) with its axis placed along the direction of wave propagation could do so. In the same paper, he showed that a periodic array of wires and rings could give rise to a negative refractive index. Pendry also proposed a related negative-permeability design, the [[Swiss roll (metamaterial)|Swiss roll]].

In 2000, [[David R. Smith (physicist)|David R. Smith]] et al. reported the experimental demonstration of functioning electromagnetic metamaterials by horizontally stacking, [[periodic function|periodically]], [[split-ring resonator]]s and thin wire structures. A method was provided in 2002 to realize negative-index metamaterials using artificial lumped-element loaded transmission lines in [[microstrip]] technology. In 2003, complex (both real and imaginary parts of) negative refractive index<ref>AIP News, Number 628 #1, March 13 Physics Today, May 2003, Press conference at APS March Meeting, Austin, Texas, March 4, 2003, New Scientist, vol 177, p. 24.</ref>  and imaging by flat lens<ref>{{cite journal|pmid=14647372|year=2003|last1=Parimi|first1=P. V.|title=Photonic crystals: Imaging by flat lens using negative refraction|journal=Nature|volume=426|issue=6965|pages=404|last2=Lu|first2=W. T.|last3=Vodo|first3=P|last4=Sridhar|first4=S|doi=10.1038/426404a|bibcode=2003Natur.426..404P|s2cid=4411307|doi-access=free}}</ref> using left handed metamaterials were demonstrated. By 2007, experiments that involved [[negative refractive index]] had been conducted by many groups.<ref name="physicsengineering1" /><ref name="radiation-properties" /> At microwave frequencies, the first, imperfect [[cloaking device|invisibility cloak]] was realized in 2006.<ref name="kock1">{{cite journal|author=Kock, W. E.|journal=IRE Proc.|volume=34|year=1946|pages=828–36|title=Metal-Lens Antennas|doi=10.1109/JRPROC.1946.232264|issue=11|s2cid=51658054}}</ref><ref name="kock2">{{cite journal|author=Kock, W.E.|journal=Bell Syst. Tech. J.|volume=27|year=1948|title=Metallic Delay Lenses|pages=58–82|doi=10.1002/j.1538-7305.1948.tb01331.x}}</ref><ref name="caloz">{{cite journal|author1=Caloz, C.|author2=Chang, C.-C.|author3=Itoh, T.|title=Full-wave verification of the fundamental properties of left-handed materials in waveguide configurations|journal=J. Appl. Phys.|url=http://xlab.me.berkeley.edu/MURI/publications/publications_9.pdf|year=2001|volume=90|page=11|doi=10.1063/1.1408261|bibcode=2001JAP....90.5483C|issue=11|access-date=2009-05-17|archive-date=2021-09-16|archive-url=https://web.archive.org/web/20210916205833/http://xlab.me.berkeley.edu/MURI/publications/publications_9.pdf|url-status=dead}}</ref><ref name="IEEEMTT-V50">{{cite journal|author1=Eleftheriades, G.V. |author2=Iyer A.K. |author3=Kremer, P.C.  |name-list-style=amp |title=Planar Negative Refractive Index Media Using Periodically L-C Loaded Transmission Lines|journal=[[IEEE Transactions on Microwave Theory and Techniques]]|volume=50|pages=2702–12|year=2002|doi=10.1109/TMTT.2002.805197|bibcode = 2002ITMTT..50.2702E|issue =12 }}</ref><ref name="Caloz-V2">{{cite book|author1=Caloz, C.  |author2=Itoh, T. |title=IEEE Antennas and Propagation Society International Symposium (IEEE Cat. No.02CH37313) |chapter=Application of the transmission line theory of left-handed (LH) materials to the realization of a microstrip "LH line" |volume=2|page=412|year=2002|doi=10.1109/APS.2002.1016111|isbn =978-0-7803-7330-3|s2cid=108405740 }}</ref>

From the standpoint of governing equations, contemporary researchers can classify the realm of metamaterials into three primary branches:<ref name="c1">{{cite journal |author1=Yang, F.B.; Zhang, Z.R.; Xu, L.J.; Liu, Z.F.; Jin, P.; Zhuang, P.F.; Lei, M.; Liu, J.R.; Jiang, J.-H.; Ouyang, X.P.; Marchesoni, F.; Huang, J.P. |title=Controlling mass and energy diffusion with metamaterials |journal=Rev. Mod. Phys. |date=2024 |volume=96 |issue=1 |page=015002 |arxiv=2309.04711 |doi=10.1103/RevModPhys.96.015002 |bibcode=2024RvMP...96a5002Y }}</ref> Electromagnetic/Optical wave metamaterials, other wave metamaterials, and [[diffusion metamaterial]]s. These branches are characterized by their respective governing equations, which include Maxwell's equations (a wave equation describing transverse waves), other wave equations (for longitudinal and transverse waves), and diffusion equations (pertaining to diffusion processes).<ref>{{cite book |author1=Yang, F.B.; Huang, J.P. |title=Diffusionics: Diffusion Process Controlled by Diffusion Metamaterials |date=2024 |publisher=Springer |location=Singapore |id={{ASIN|9819704863|country=ca}} }}</ref> Crafted to govern a range of diffusion activities, diffusion metamaterials prioritize diffusion length as their central metric. This crucial parameter experiences temporal fluctuations while remaining immune to frequency variations. In contrast, wave metamaterials, designed to adjust various wave propagation paths, consider the wavelength of incoming waves as their essential metric. This wavelength remains constant over time, though it adjusts with frequency alterations. Fundamentally, the key metrics for diffusion and wave metamaterials present a stark divergence, underscoring a distinct complementary relationship between them. For comprehensive information, refer to Section I.B, "Evolution of metamaterial physics," in Ref.<ref name="c1"/>