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  1. Article ; Online: Exploring localized ENZ resonances and their role in superscattering, wideband invisibility, and tunable scattering.

    Serebryannikov, Andriy E / Ozbay, Ekmel

    Scientific reports

    2024  Volume 14, Issue 1, Page(s) 1580

    Abstract: While the role and manifestations of the localized surface plasmon resonances (LSPRs) in anomalous scattering, like superscattering and invisibility, are quite well explored, the existence, appearance, and possible contribution of localized epsilon-near- ... ...

    Abstract While the role and manifestations of the localized surface plasmon resonances (LSPRs) in anomalous scattering, like superscattering and invisibility, are quite well explored, the existence, appearance, and possible contribution of localized epsilon-near-zero (ENZ) resonances still invoke careful exploration. In this paper, that is done along with a comparison of the resonances of two types in the case of thin-wall cylinders made of lossy and loss-compensated dispersive materials. It is shown that the localized ENZ resonances exist and appear very close to the zero-permittivity regime, i.e., at near-zero but yet negative permittivity that is similar to the ENZ modes in thin planar films. Near- and far-field characteristics of the superscattering modes are investigated. The results indicate that the scattering regimes arising due to LSPRs and localized ENZ resonances are distinguishable in terms of the basic field features inside and around the scatterer and differ in their contribution to the resulting scattering mechanism, e.g., in terms of the occupied frequency and permittivity ranges as well as the sensitivity to the wall thickness variations. When the losses are either weak or tend to zero due to the doping with gain enabling impurities, the sharp peaks of the scattering cross-section that are yielded by the resonances can be said to be embedded into the otherwise wide invisibility range. In the case of lossy material, a wide and continuous invisibility range is shown to appear not only due to a small total volume of the scatterer in the nonresonant regime, but also because high-Q superscattering modes are suppressed by the losses. For numerical demonstration, indium antimonide, a natural lossy material, and a hypothetical, properly doped material with the same real part of the permittivity but lower or zero losses are considered. In the latter case, variations of permittivity with a control parameter can be adjusted in such a way that transitions from one superscattering mode to another can be achieved. In turn, transition from the strong-scattering to the invisibility regime is possible even for the original lossy material. The basic properties of the studied superscattering modes may be replicable in artificial structures comprising natural low-loss materials.
    Language English
    Publishing date 2024-01-18
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-024-51503-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Using Thin Films of Phase-Change Material for Active Tuning of Terahertz Waves Scattering on Dielectric Cylinders.

    Cakmak, Atilla Ozgur / Colak, Evrim / Serebryannikov, Andriy E

    Materials (Basel, Switzerland)

    2024  Volume 17, Issue 1

    Abstract: The scattering of electromagnetic waves by isotropic dielectric cylinders can be dramatically modified by means of vanadium dioxide (VO2) thin-film coatings. Efficient dynamic control of scattering is achieved due to the variations in material parameters ...

    Abstract The scattering of electromagnetic waves by isotropic dielectric cylinders can be dramatically modified by means of vanadium dioxide (VO2) thin-film coatings. Efficient dynamic control of scattering is achieved due to the variations in material parameters realizable by means of external biasing. In this paper, we study the scattering of terahertz waves in a case where the coating shells are made of VO2, a phase-change material, whose thin films may work rather as electromagnetic phase screens in the insulator material phase, but as lossy quasi-metallic components in the metallic material phase. The shells that uniformly cover the dielectric cylinders are investigated. Attention will be paid to the demonstration of the potential of VO2 in the external control of diverse scattering regimes of the dielectric-VO2 core-shell scatterer, while conductivity of VO2 corresponds to rather insignificant variations in temperature. In line with the purposes of this work, it is shown that the different resonant and nonresonant regimes have different sensitivity to the variations in VO2 conductivity. Both the total scattering cross section and field distributions inside and around the core are studied, as well as the angle-dependent scattering cross section.
    Language English
    Publishing date 2024-01-04
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma17010260
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Transmissive terahertz metasurfaces with vanadium dioxide split-rings and grids for switchable asymmetric polarization manipulation.

    Serebryannikov, Andriy E / Lakhtakia, Akhlesh / Vandenbosch, Guy A E / Ozbay, Ekmel

    Scientific reports

    2022  Volume 12, Issue 1, Page(s) 3518

    Abstract: Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO[Formula: see text]), a phase-change material can deliver switching between (1) polarization manipulation in ... ...

    Abstract Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO[Formula: see text]), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO[Formula: see text]. As the meta-atom arrays function as arrays of metallic subwavelength resonators for the metallic phase of VO[Formula: see text], but as transmissive phase screens for the insulator phase of VO[Formula: see text], numerical simulations of double- and triple-array metasurfaces strongly indicate extreme scenarios of functionality switching also when the resulting structure comprises only VO[Formula: see text] meta-atoms and VO[Formula: see text] grids. More switching scenarios are achievable when only one meta-atom array or one grid is made of VO[Formula: see text] components. They are enabled by the efficient coupling of the geometrically identical resonator arrays/grids that are made of the materials that strongly differ in terms of conductivity, i.e. Cu and VO[Formula: see text] in the metallic phase.
    Language English
    Publishing date 2022-03-03
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-022-07265-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Multifunctional tunable gradient metasurfaces for terahertz beam splitting and light absorption.

    Erçağlar, Veysel / Hajian, Hodjat / Serebryannikov, Andriy E / Ozbay, Ekmel

    Optics letters

    2021  Volume 46, Issue 16, Page(s) 3953–3956

    Abstract: Obtaining functional devices with tunable features is beneficial to advance terahertz (THz) science and technology. Here, we propose multifunctional gradient metasurfaces that are composed of a periodic array of binary Si microcylinders integrated ... ...

    Abstract Obtaining functional devices with tunable features is beneficial to advance terahertz (THz) science and technology. Here, we propose multifunctional gradient metasurfaces that are composed of a periodic array of binary Si microcylinders integrated with
    Language English
    Publishing date 2021-07-28
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.435197
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: One-way and near-absolute polarization insensitive near-perfect absorption by using an all-dielectric metasurface.

    Yildirim, Deniz Umut / Ghobadi, Amir / Soydan, Mahmut Can / Serebryannikov, Andriy E / Ozbay, Ekmel

    Optics letters

    2020  Volume 45, Issue 7, Page(s) 2010–2013

    Abstract: In this Letter, we numerically propose the one-way perfect absorption of near-infrared radiation in a tunable spectral range with high transmission in the neighboring spectral ranges. This functionality is obtained by using a two-dimensional, guided-mode ...

    Abstract In this Letter, we numerically propose the one-way perfect absorption of near-infrared radiation in a tunable spectral range with high transmission in the neighboring spectral ranges. This functionality is obtained by using a two-dimensional, guided-mode resonance-based grating-waveguide metasurface that acts as a frequency-selective reflector, a spacer dielectric, and an absorbing oxide layer. Within the bandwidth of the excited guided-mode resonance excited at 1.82 µm (with a full-width at half-maximum of 19 nm), we confirmed perfect absorption when light was incident from one of the two opposite directions, whereas in the other direction, perfect reflection was observed. The forward-to-backward absorption ratio reached as high as 60, while the thickness of the entire structure was on the order of the operating wavelength. In addition to the spectral tunability of the excited resonances and their bandwidths, our proposed device supports transparency windows with 65% transmission in the adjacent frequency bands. Our 2D grating is also verified to enable near-absolute insensitivity to the polarization state of incident light. Geometrical parameter modification also gives our design great tunability, as we also designed a device with a 300 nm absorption/reflection linewidth.
    Language English
    Publishing date 2020-04-01
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.387350
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Thermally sensitive scattering of terahertz waves by coated cylinders for tunable invisibility and masking.

    Serebryannikov, Andriy E / Alici, Kamil B / Ozbay, Ekmel / Lakhtakia, Akhlesh

    Optics express

    2018  Volume 26, Issue 1, Page(s) 1–14

    Abstract: Temperature-sensitive scattering of terahertz (THz) waves by infinitely long, cylindrical core-shell structures was theoretically studied. Each structure is a dielectric cylinder coated with an InSb shell illuminated by either a transverse-electric (TE) ... ...

    Abstract Temperature-sensitive scattering of terahertz (THz) waves by infinitely long, cylindrical core-shell structures was theoretically studied. Each structure is a dielectric cylinder coated with an InSb shell illuminated by either a transverse-electric (TE) or a transverse-magnetic (TM) plane wave. InSb is a thermally tunable semiconductor showing a transition from dielectric to plasmonic state at THz frequencies. Accordingly, the total scattering efficiency (TSE) can be thermally tuned for both polarization states of the incident plane wave. The spectral locations of the maxima and minima of the TSE of an InSb-coated cylinder can be exploited for cloaking the core. At least three scenarios lead to the strong suppression of scattering by a single core-shell structure in different spectral regimes when the temperature is fixed. The excitation of localized surface-plasmon resonances is the feature being common for two of them, while the effect of volumetric resonance dominates in the third scenario. Regimes that are either highly or weakly sensitive to the core material were identified. Weak sensitivity enables masking, i.e., the core material cannot be identified by a far-zone observer. The TSE minima are usually significantly sensitive to the polarization state, but ones with weak sensitivity to the polarization state also exist.
    Language English
    Publishing date 2018-01-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.26.000001
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Wideband switchable unidirectional transmission in a photonic crystal with a periodically nonuniform pupil.

    Serebryannikov, Andriy E / Lakhtakia, Akhlesh

    Optics letters

    2013  Volume 38, Issue 17, Page(s) 3279–3282

    Abstract: Wideband switchable diode-like transmission can be exhibited by an asymmetric dielectric photonic crystal, when the host medium is changed from air to a coherent atomic gas (CAG), a strongly dispersive medium. Significant modification of diffraction- ... ...

    Abstract Wideband switchable diode-like transmission can be exhibited by an asymmetric dielectric photonic crystal, when the host medium is changed from air to a coherent atomic gas (CAG), a strongly dispersive medium. Significant modification of diffraction-enabled one-way transmission due to the CAG is possible in both frequency and incidence-angle domains in the short-wave infrared regime. In particular, new one-way and high-contrast passbands, which are as much as 1.0 THz in bandwidth, can appear at fixed incidence angle within a stop band of the CAG-free structure and tuned by varying the oscillator strength of the CAG. These passbands correspond to relatively small, either positive or negative, values of the dielectric susceptibility of the CAG.
    Language English
    Publishing date 2013-09-01
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.38.003279
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  8. Article ; Online: Light guiding, bending, and splitting via local modification of interfaces of a photonic waveguide.

    Vashistha, Vishal / Krawczyk, Maciej / Serebryannikov, Andriy E / A E Vandenbosch, Guy

    Optics letters

    2019  Volume 44, Issue 19, Page(s) 4725–4728

    Abstract: A general approach to the surface control of the localization, guiding, and redirecting of volume-mode light in photonic waveguides via tailoring their interfaces (surfaces) is proposed. The approach is demonstrated for dielectric rod-type photonic ... ...

    Abstract A general approach to the surface control of the localization, guiding, and redirecting of volume-mode light in photonic waveguides via tailoring their interfaces (surfaces) is proposed. The approach is demonstrated for dielectric rod-type photonic crystal slabs, whose regular and defect parts are distinguished by whether the nanocylinders are covered by metal caps. Thus, the rod-array part of the structure is not changed, while the local modifications are only applied to the interfaces. The basic functionalities, i.e., localized volume wave guiding, bending, and splitting are achievable. Selective dual-mode operation is possible due to the co-existence of a defect mode and a chainlike mode in one structure.
    Language English
    Publishing date 2019-10-07
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.44.004725
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  9. Article ; Online: Broadband mixing of [Formula: see text]-symmetric and [Formula: see text]-broken phases in photonic heterostructures with a one-dimensional loss/gain bilayer.

    Özgün, Ege / Serebryannikov, Andriy E / Ozbay, Ekmel / Soukoulis, Costas M

    Scientific reports

    2017  Volume 7, Issue 1, Page(s) 15504

    Abstract: Combining loss and gain components in one photonic heterostructure opens a new route to efficient manipulation by radiation, transmission, absorption, and scattering of electromagnetic waves. Therefore, loss/gain structures enabling [Formula: see text]- ... ...

    Abstract Combining loss and gain components in one photonic heterostructure opens a new route to efficient manipulation by radiation, transmission, absorption, and scattering of electromagnetic waves. Therefore, loss/gain structures enabling [Formula: see text]-symmetric and [Formula: see text]-broken phases for eigenvalues have extensively been studied in the last decade. In particular, translation from one phase to another, which occurs at the critical point in the two-channel structures with one-dimensional loss/gain components, is often associated with one-way transmission. In this report, broadband mixing of the [Formula: see text]-symmetric and [Formula: see text]-broken phases for eigenvalues is theoretically demonstrated in heterostructures with four channels obtained by combining a one-dimensional loss/gain bilayer and one or two thin polarization-converting components (PCCs). The broadband phase mixing in the four-channel case is expected to yield advanced transmission and absorption regimes. Various configurations are analyzed, which are distinguished in symmetry properties and polarization conversion regime of PCCs. The conditions necessary for phase mixing are discussed. The simplest two-component configurations with broadband mixing are found, as well as the more complex three-component configurations wherein symmetric and broken sets are not yet mixed and appear in the neighbouring frequency ranges. Peculiarities of eigenvalue behaviour are considered for different permittivity ranges of loss/gain medium, i.e., from epsilon-near-zero to high-epsilon regime.
    Language English
    Publishing date 2017-11-14
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-017-14982-w
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Temperature-mediated invocation of the vacuum state for switchable ultrawide-angle and broadband deflection.

    Serebryannikov, Andriy E / Lakhtakia, Akhlesh / Aalizadeh, Majid / Ozbay, Ekmel / Vandenbosch, Guy A E

    Scientific reports

    2018  Volume 8, Issue 1, Page(s) 15044

    Abstract: Temperature-mediated appearance and disappearance of a deflection grating in a diffracting structure is possible by employing InSb as the grating material. InSb transits from the dielectric state to the plasmonic state in the terahertz regime as the ... ...

    Abstract Temperature-mediated appearance and disappearance of a deflection grating in a diffracting structure is possible by employing InSb as the grating material. InSb transits from the dielectric state to the plasmonic state in the terahertz regime as the temperature increases, this transition being reversible. An intermediate state is the vacuum state in which the real part of the relative permittivity of InSb equals unity while the imaginary part is much smaller. Then the grating virtually disappears, deflection being impossible as only specular reflection can occur. This ON/OFF switching of deflection and relevant angular filtering are realizable over wide ranges of frequency and incidence angle by a temperature change of as low as 20 K. The vacuum state of InSb invoked for ON/OFF switching of deflection and relevant angular filtering can also be obtained for thermally tunable materials other than InSb as well as by using non-thermal mechanisms.
    Language English
    Publishing date 2018-10-09
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-018-32977-z
    Database MEDical Literature Analysis and Retrieval System OnLINE

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