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  1. Article ; Online: Perturbation theory for Kerr nonlinear leaky cavities.

    Christopoulos, Thomas / Tsilipakos, Odysseas / Kriezis, Emmanouil E

    Optics letters

    2020  Volume 45, Issue 23, Page(s) 6442–6445

    Abstract: In emerging open photonic resonators that support quasinormal eigenmodes, fundamental physical quantities and methods have to be carefully redefined. Here, we develop a perturbation theory framework for nonlinear material perturbations in leaky optical ... ...

    Abstract In emerging open photonic resonators that support quasinormal eigenmodes, fundamental physical quantities and methods have to be carefully redefined. Here, we develop a perturbation theory framework for nonlinear material perturbations in leaky optical cavities. The ambiguity in specifying the stored energy due to the exponential growth of the quasinormal mode field profile is lifted by implicitly specifying it via the accompanying resistive loss. The capabilities of the framework are demonstrated by considering a third-order nonlinear ring resonator and verified by comparing against full-wave nonlinear finite element simulations. The developed theory allows for efficiently modeling nonlinear phenomena in contemporary photonic resonators with radiation and resistive loss.
    Language English
    Publishing date 2020-12-01
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.408336
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: 2D-patterned graphene metasurfaces for efficient third harmonic generation at THz frequencies.

    Theodosi, Anna / Tsilipakos, Odysseas / Soukoulis, Costas M / Economou, Eleftherios N / Kafesaki, Maria

    Optics express

    2022  Volume 30, Issue 1, Page(s) 460–472

    Abstract: Graphene is an attractive two-dimensional material for nonlinear applications in the THz regime, since it possesses high third order nonlinearity and the ability to support tightly confined surface plasmons. Here, we study 2D-patterned graphene-patch ... ...

    Abstract Graphene is an attractive two-dimensional material for nonlinear applications in the THz regime, since it possesses high third order nonlinearity and the ability to support tightly confined surface plasmons. Here, we study 2D-patterned graphene-patch metasurfaces for efficient third harmonic generation. The efficiency of the nonlinear process is enhanced by spectrally aligning the fundamental and third harmonic frequencies with resonances of the metasurface, leading to spatiotemporal energy confinement in both steps of excitation at ω and radiation at 3ω. This precise resonance alignment is enabled by the 2D-patterning; it is achieved by modifying the dispersion of the underlying plasmons and, thus, the spectral positions of the supported standing wave resonances. Efficiencies as high as -20dB (1%) for input intensity 0.1 MW/cm
    Language English
    Publishing date 2022-02-21
    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.445751
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Meta-Atoms with Toroidal Topology for Strongly Resonant Responses.

    Tsilipakos, Odysseas / Viskadourakis, Zacharias / Tasolamprou, Anna C / Zografopoulos, Dimitrios C / Kafesaki, Maria / Kenanakis, George / Economou, Eleftherios N

    Micromachines

    2023  Volume 14, Issue 2

    Abstract: A conductive meta-atom of toroidal topology is studied both theoretically and experimentally, demonstrating a sharp and highly controllable resonant response. Simulations are performed both for a free-space periodic metasurface and a pair of meta-atoms ... ...

    Abstract A conductive meta-atom of toroidal topology is studied both theoretically and experimentally, demonstrating a sharp and highly controllable resonant response. Simulations are performed both for a free-space periodic metasurface and a pair of meta-atoms inserted within a rectangular metallic waveguide. A quasi-dark state with controllable radiative coupling is supported, allowing to tune the linewidth (quality factor) and lineshape of the supported resonance via the appropriate geometric parameters. By conducting a rigorous multipole analysis, we find that despite the strong toroidal dipole moment, it is the residual electric dipole moment that dictates the electromagnetic response. Subsequently, the structure is fabricated with 3D printing and coated with silver paste. Importantly, the structure is planar, consists of a single metallization layer and does not require a substrate when neighboring meta-atoms are touching, resulting in a practical, thin and potentially low-loss system. Measurements are performed in the 5 GHz regime with a vector network analyzer and a good agreement with simulations is demonstrated.
    Language English
    Publishing date 2023-02-17
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2620864-7
    ISSN 2072-666X
    ISSN 2072-666X
    DOI 10.3390/mi14020468
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Photo-elasticity of silk fibroin harnessing whispering gallery modes.

    Korakas, Nikolaos / Vurro, Davide / Tsilipakos, Odysseas / Vasileiadis, Thomas / Graczykowski, Bartlomiej / Cucinotta, Annamaria / Selleri, Stefano / Fytas, George / Iannotta, Salvatore / Pissadakis, Stavros

    Scientific reports

    2023  Volume 13, Issue 1, Page(s) 9750

    Abstract: Silk fibroin is an important biomaterial for photonic devices in wearable systems. The functionality of such devices is inherently influenced by the stimulation from elastic deformations, which are mutually coupled through photo-elasticity. Here, we ... ...

    Abstract Silk fibroin is an important biomaterial for photonic devices in wearable systems. The functionality of such devices is inherently influenced by the stimulation from elastic deformations, which are mutually coupled through photo-elasticity. Here, we investigate the photo-elasticity of silk fibroin employing optical whispering gallery mode resonation of light at the wavelength of 1550 nm. The fabricated amorphous (Silk I) and thermally-annealed semi-crystalline structure (Silk II) silk fibroin thin film cavities display typical Q-factors of about 1.6 × 10
    MeSH term(s) Fibroins/chemistry ; Silk/chemistry ; Elastic Modulus ; Biocompatible Materials ; Optics and Photonics
    Chemical Substances Fibroins (9007-76-5) ; Silk ; Biocompatible Materials
    Language English
    Publishing date 2023-06-16
    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/s41598-023-36400-0
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article: Fabrication of mm-Scale Complementary Split Ring Resonators, for Potential Application as Water Pollution Sensors.

    Viskadourakis, Zacharias / Fanourakis, George / Tamiolakis, Evangelos / Theodosi, Anna / Katsara, Klytaimnistra / Vrithias, Nikolaos Rafael / Tsilipakos, Odysseas / Kenanakis, George

    Materials (Basel, Switzerland)

    2023  Volume 16, Issue 15

    Abstract: Rectangular, millimeter-scale complementary split ring resonators were fabricated, employing the so-called Computer Numerical Control method, combined with a home-built mechanical engraver. Their electromagnetic performance was thoroughly investigated ... ...

    Abstract Rectangular, millimeter-scale complementary split ring resonators were fabricated, employing the so-called Computer Numerical Control method, combined with a home-built mechanical engraver. Their electromagnetic performance was thoroughly investigated with respect to their dimensions in the frequency regime between 2 and 9 GHz via combining experiments and corresponding theoretical simulations, wherein a considerably effective consistency was obtained. Moreover, their sensing response was extensively investigated against various aqueous solutions enriched with typical fertilizers used in agriculture, as well as detergents commonly used in every-day life. Corresponding experimental results evidently establish the capability of the studied metasurfaces as potential sensors against water pollution.
    Language English
    Publishing date 2023-07-27
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma16155290
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Antimatched Electromagnetic Metasurfaces for Broadband Arbitrary Phase Manipulation in Reflection.

    Tsilipakos, Odysseas / Koschny, Thomas / Soukoulis, Costas M

    ACS photonics

    2018  Volume 5, Issue 3, Page(s) 1101–1107

    Abstract: Metasurfaces impart phase discontinuities on impinging electromagnetic waves that are typically limited to 0-2π. Here, we demonstrate that multiresonant metasurfaces can break free from this limitation and supply arbitrarily large, tunable time delays ... ...

    Abstract Metasurfaces impart phase discontinuities on impinging electromagnetic waves that are typically limited to 0-2π. Here, we demonstrate that multiresonant metasurfaces can break free from this limitation and supply arbitrarily large, tunable time delays over ultrawide bandwidths. As such, ultrathin metasurfaces can act as the equivalent of thick bulk structures by emulating the multiple geometric resonances of three-dimensional systems that originate from phase accumulation with effective material resonances implemented on the surface itself via suitable subwavelength meta-atoms. We describe a constructive procedure for defining the required sheet admittivities of such metasurfaces. Importantly, the proposed approach provides an exactly linear phase response so that broadband pulses can experience the desired group delay without any distortion of the pulse shape. We focus on operation in reflection by exploiting an antimatching condition, satisfied by interleaved electric and magnetic Lorentzian resonances in the surface admittivities, which completely zeroes out transmission through the metasurface. As a result, the proposed metasurfaces can perfectly reflect a broadband pulse imparting a prescribed group delay. The group delay can be tuned by modifying the implemented resonances, thus opening up diverse possibilities in the temporal applications of metasurfaces.
    Language English
    Publishing date 2018-01-03
    Publishing country United States
    Document type Journal Article
    ISSN 2330-4022
    ISSN 2330-4022
    DOI 10.1021/acsphotonics.7b01415
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: On the calculation of the quality factor in contemporary photonic resonant structures.

    Christopoulos, Thomas / Tsilipakos, Odysseas / Sinatkas, Georgios / Kriezis, Emmanouil E

    Optics express

    2019  Volume 27, Issue 10, Page(s) 14505–14522

    Abstract: The correct numerical calculation of the resonance characteristics and, principally, the quality factor Q of contemporary photonic and plasmonic resonant systems is of utmost importance, since Q defines the bandwidth and affects nonlinear and spontaneous ...

    Abstract The correct numerical calculation of the resonance characteristics and, principally, the quality factor Q of contemporary photonic and plasmonic resonant systems is of utmost importance, since Q defines the bandwidth and affects nonlinear and spontaneous emission processes. Here, we comparatively assess the commonly used methods for calculating Q using spectral simulations with commercially available, general-purpose software. We study the applicability range of these methods through judiciously selected examples covering different material systems and frequency regimes from the far-infrared to the visible. We take care in highlighting the underlying physical and numerical reasons limiting the applicability of each one. Our findings demonstrate that in contemporary systems (plasmonics, 2D materials) Q calculation is not trivial, mainly due to the physical complication of strong material dispersion and light leakage. Our work can act as a reference for the mindful and accurate calculation of the quality factor and can serve as a handbook for its evaluation in guided-wave and free-space photonic and plasmonic resonant systems.
    Language English
    Publishing date 2019-06-03
    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.27.014505
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Perfect optical absorption with nanostructured metal films: design and experimental demonstration.

    Perrakis, George / Tsilipakos, Odysseas / Kenanakis, George / Kafesaki, Maria / Soukoulis, Costas M / Economou, Eleftherios N

    Optics express

    2019  Volume 27, Issue 5, Page(s) 6842–6850

    Abstract: Structuring metal surfaces on the nanoscale has been shown to alter their fundamental processes like reflection or absorption by supporting surface plasmon resonances. Here, we propose metal films with subwavelength rectangular nanostructuring that ... ...

    Abstract Structuring metal surfaces on the nanoscale has been shown to alter their fundamental processes like reflection or absorption by supporting surface plasmon resonances. Here, we propose metal films with subwavelength rectangular nanostructuring that perfectly absorb the incident radiation in the optical regime. The structures are fabricated with low-cost nanoimprint lithography and thus constitute an appealing alternative to elaborate absorber designs with complex meta-atoms or multilayer structuring. We conduct a thorough numerical analysis to gain physical insight on how the key structural parameters affect the optical response and identify the designs leading to broad spectral and angular bandwidths, both of which are highly desirable in practical absorber applications. Subsequently, we fabricate and measure the structures with an FT-IR spectrometer demonstrating very good agreement with theory. Finally, we assess the performance of the proposed structures as sensing devices by quantifying the dependence of the absorption peak frequency position on the superstrate material.
    Language English
    Publishing date 2019-03-15
    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.27.006842
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Book ; Online: Chapter Merging Plasmonics and Silicon Photonics Towards Greener and Faster "Network-on-Chip" Solutions for Data Centers and High-Performance Computing Systems

    Papaioannou, Sotirios / Markey, Laurent / Dereux, Alain / Kumar, Ashwani / Bozhevolnyi, Sergey I. / Suna, Alpaslan / Villasante, Oriol Gili de / Tekin, Tolga / Waldow, Michael / Tsilipakos, Odysseas / Pitilakis, Alexandros / Vyrsokinos, Konstantinos / Kriezis, Emmanouil E. / Pleros, Nikos / Kalavrouziotis, Dimitrios / Giannoulis, Giannis / Apostolopoulos, Dimitrios / Avramopoulos, Hercules / Zacharatos, Filimon /
    Hassan, Karim / Weeber, Jean-Claude

    2012  

    Keywords Endocrinology ; Medicine
    Size 1 Online-Ressource
    Publisher InTechOpen
    Document type Book ; Online
    Note English ; Open Access
    HBZ-ID HT021047319
    Database ZB MED Catalogue: Medicine, Health, Nutrition, Environment, Agriculture

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  10. Article ; Online: Split-cube-resonator-based metamaterials for polarization-selective asymmetric perfect absorption.

    Tsilipakos, Odysseas / Xomalis, Angelos / Kenanakis, George / Farsari, Maria / Soukoulis, Costas M / Economou, Eleftherios N / Kafesaki, Maria

    Scientific reports

    2020  Volume 10, Issue 1, Page(s) 17653

    Abstract: A split-cube-resonator-based metamaterial structure that can act as a polarization- and direction-selective perfect absorber for the infrared region is theoretically and experimentally demonstrated. The structure, fabricated by direct laser writing and ... ...

    Abstract A split-cube-resonator-based metamaterial structure that can act as a polarization- and direction-selective perfect absorber for the infrared region is theoretically and experimentally demonstrated. The structure, fabricated by direct laser writing and electroless silver plating, is comprised of four layers of conductively-coupled split-cube magnetic resonators, appropriately rotated to each other to bestow the desired electromagnetic properties. We show narrowband polarization-selective perfect absorption when the structure is illuminated from one side; the situation is reversed when illuminating from the other side, with the orthogonal linear polarization being absorbed. The absorption peak can be tuned in a wide frequency range by a sparser or denser arrangement of the split cube resonators, allowing to cover the entire atmospheric transparency window. The proposed metamaterial structure can find applications in polarization-selective thermal emission at the IR atmospheric transparency window for radiative cooling, in cost-effective infrared sensing devices, and in narrowband filters and linear polarizers in reflection mode.
    Language English
    Publishing date 2020-10-19
    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/s41598-020-74221-7
    Database MEDical Literature Analysis and Retrieval System OnLINE

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