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[[Vol. 26]Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelength Photonics _ WPI-MANA.pdf](https://mdr.nims.go.jp/filesets/8a1e6fff-7de2-4119-9125-31b649f26101/download)

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International Center for Materials Nanoarchitectonics (WPI-MANA)

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[[Research Highlights Vol.26] Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelength Photonics](https://mdr.nims.go.jp/datasets/9251d152-4648-4127-a419-2439b4777954)

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2022/04/04 10:13 Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelength Photonics | MANAhttps://www.nims.go.jp/mana/research/highlights/vol26.html 1/3Previous  Index  NextResearch Highlights[Vol. 26]Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelengthPhotonics15 Jun, 2016A new class of optical topological transitions in electromagnetic metamaterials inducedby the non-locality of the electromagnetic response is reported.Figure 1: a-f, Iso-frequency curves of the multilayer HMM in kx-ky-kz space (a-c) and in kτ-kn space (d–f)at ω/ωp = ωc/ωp+Δ (a, d), ω/ωp = ωc/ωp (b, e) and ω/ωp = ωc/ωp−Δ (c, f). Panel (g) shows theevolution of iso-frequency curve with frequency, in the range ωc/ωp−Δ ≤ ω/ωp ≤ ωc/ωp+Δ. The iso-frequency curves in panels d-f are superimposed in panel g with the same colors. Throughout the entireplot, c is the speed of light, ωp is the plasma frequency of the metal layer consisting HMM, kp = ωp/c andΔ = 2.5×10-5.https://www.nims.go.jp/mana/research/highlights/vol25.htmlhttps://www.nims.go.jp/mana/research/highlights/index.htmlhttps://www.nims.go.jp/mana/research/highlights/vol27.html2022/04/04 10:13 Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelength Photonics | MANAhttps://www.nims.go.jp/mana/research/highlights/vol26.html 2/3Figure 2: Schematic of light propagating through a hyperbolicmetamaterial (HMM) in a critical state where the effectiverefractive index is zero. Blue and gray stripes represent metaland dielectric layers, respectively.Materials scientists can produce sub-wavelength artificial structures (split rings, honeycomb shapesand many more) to interact with electromagnetic waves so that the propagation of waves can bearbitrarily controlled to achieve desired effects. Among the myriad of these ‘metamaterials’, metal-dielectric periodic multilayers--hyperbolic metamaterials (HMMs)--are of particular interest. In spiteof their simple structure, HMMs have the potential for unique optical applications including super-resolution lens, sub-wavelength interference and enhancing the emission of single-photon sources.Now, Satoshi Ishii, at the International Center for Materials Nanoarchitectonics (MANA), NIMS, andEvgenii Narimanov at Purdue University, USA, analytically describe non-local optical topologicaltransition in HMMs for the first time and unveil unique optical properties at the critical states.So far, most researchers have treated HMMs as effectively homogenous media based on effectivemedium theory. Following this theory, an HMM behaves either like a ‘metal’ (reflects light) or like a‘dielectric’ (refracts light in the negative direction) depending on the frequency of incident light.In this research, the scientists succeeded in analytically demonstrating the transition betweenthese two types of states induced by the non-local topological transition (see Figure 1).Furthermore, they found that in response to incoming light at the critical state, an HMM exhibitspeculiar optical properties such that its effective refractive index is zero (see Figure 2) and therefraction becomes conical.Based on these findings, the team is going to apply HMMs for the development of novelnanophotonic elements and photonic integrated circuits by an in-depth analysis of the criticalstates caused by the non-local topological transitions.Reference"Non-local Optical Topological Transitions and Critical States in Electromagnetic Metamaterials"Satoshi Ishii and Evgemii NarimanovJournal : Scientific Reports 5 (2015) 17824.https://samurai.nims.go.jp/profiles/sishii?locale=en2022/04/04 10:13 Electromagnetic Metamaterials with Zero-refractive Index for Sub-wavelength Photonics | MANAhttps://www.nims.go.jp/mana/research/highlights/vol26.html 3/3DOI : 10.1038/srep17824AffiliationsInternational Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for MaterialsScience (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, JapanContact informationInternational Center for Materials Nanoarchitectonics(WPI-MANA)National Institute for Materials Science1-1 Namiki, Tsukuba, Ibaraki 305-0044 JapanPhone: +81-29-860-4710E-mail: mana-pr[AT]ml.nims.go.jphttps://www.nature.com/articles/srep17824