Browsing by Department "Sergei Tretiakov Group"

Now showing 1 - 9 of 9
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    All-dielectric metamirror for independent and asymmetric wave-front control
    (American Physical Society, 2019-11-25) Odit, M. A.; Sayanskiy, A. D.; Asadchy, Viktar; Kapitanova, P.; Tretyakov, S. A.; Belov, P. A.; ITMO University; Sergei Tretiakov Group; Department of Electronics and Nanoengineering
    We report on the design and the numerical and experimental characterization of an all-dielectric reflecting focusing metasurface (metamirror) which does not have a back reflector, but effectively reflects incident waves with the desired reflection phase gradient. The profile of the reflection phase can be tuned independently for both sides of the single-layer subwavelength-thick metamirror by properly selecting dimensions of its dielectric inclusions. Such a feature stems from the bianisotropic omega properties of the inclusions. To demonstrate independent control of the reflection phase, we have designed a metamirror focusing normally incident plane waves at different focal distances being illuminated from the opposite sides. The proposed two-sided metamirror can find applications in antennas, diffraction gratings, and complex holograms. The absence of conducting elements makes it a perfect candidate for optical applications requiring asymmetric wave-front control.
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    Effective-medium model of wire metamaterials in the problems of radiative heat transfer
    (2014) Mirmoosa, M.S.; Ruting, F.; Nefedov, I.S.; Simovski, C.R.; Sergei Tretiakov Group; Kostantin Simovski Group; Department of Radio Science and Engineering
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    Electromagnetic energy sink
    (2015) Valagiannopoulos, Costas A.; Vehmas, Joni; Simovski, Constantin R.; Tretyakov, Sergei A.; Maslovski, Stanislav I.; Kostantin Simovski Group; Sergei Tretiakov Group; Department of Radio Science and Engineering
    The ideal black body fully absorbs all incident rays, that is, all propagating waves created by arbitrary sources. A known idealized realization of the black body is the perfectly matched layer (PML), widely used in numerical electromagnetics. However, ideal black bodies and PMLs do not interact with evanescent fields that exists near any finite-size source, and the energy stored in these fields cannot be harvested. Here, we introduce the concept of the ideal conjugate matched layer (CML), which fully absorbs the energy of both propagating and evanescent fields of sources acting as an ideal sink for electromagnetic energy. Conjugate matched absorbers have exciting application potentials, as resonant attractors of electromagnetic energy into the absorber volume. We derive the conditions on the constitutive parameters of media which can serve as CML materials, numerically study the performance of planar and cylindrical CML and discuss possible realizations of such materials as metal-dielectric composites.
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    Extreme coupling: A route towards local magnetic metamaterials
    (2014) Menzel, Christoph; Hebestreit, E.; Alaee, Rasoul; Albooyeh, Mohammad; Mühlig, Stefan; Burger, S; Rockstuhl, Carsten; Simovski, Constantin R.; Tretyakov, Sergei A.; Lederer, Falk; Pertsch, Thomas; Kostantin Simovski Group; Sergei Tretiakov Group; Department of Radio Science and Engineering
    Genuinely homogeneous metamaterials, which may be characterized by local effective constitutive relations, are required for many spectacular metamaterial applications. Such metamaterials have to be made of meta-atoms, i.e., subwavelength resonators, which exhibit only electric and or magnetic dipole and negligible higher-order multipolar polarizabilities in the spectral range of interest. Here, we show that these desired meta-atoms can be designed by exploiting the extreme coupling regime. Appropriate meta-atoms are identified by performing a multipole analysis of the field scattered from the respective meta-atom. To design those particular meta-atoms it is important to disclose the frequency and angular-dependent polarizability of both dipole moments. We demonstrate the applicability of a purely analytical model to accurately calculate for a normally incident plane wave reflection and transmission from meta-surfaces made of periodically arranged meta-atoms. With our work we identify a possible route towards the engineering of artificial materials while only considering the response from its constituents. Our approach is generally applicable to all spectral domains and can be used to evaluate and design metamaterials made from different constituting materials, e.g., metals, dielectrics, or semiconductors.
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    High-Impedance Wireless Power Transfer Transmitter Coils for Freely Positioning Receivers
    (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021) Mollaei, Masoud Sharifian Mazraeh; Jayathurathnage, Prasad; Tretyakov, Sergei A.; Simovski, Constantin R.; Kostantin Simovski Group; Sergei Tretiakov Group; Department of Electronics and Nanoengineering
    In this letter, a wireless power transfer (WPT) system based on two high-impedance coil (HIC) - cable loop antennas with a modified shield - as transmitters (Tx)s and a spiral coil as a receiver (Rx) is proposed and discussed. Utilizing features of HIC at its parallel-circuit resonance frequency, we design the Tx in a way that in the absence of the Rx, the input impedance of the Tx is very high compared to the case when the Rx is near the Tx. This feature offers a possibility for free positioning of the Rx over an array of Txs and auto self-activation and de-activation of the Txs, leading to highly efficient performance. To verify the proposed solution, we have designed, fabricated, and experimentally tested a WPT system based on two HICs as Txs and one Rx. The proposed system operates in a high-frequency range (around 280 MHz) in the near-field coupling regime. The measured averaged efficiency of the prototype is higher than 93%. The proposed system is simple, cheap, and does not require any control circuit system for tuning the system when the receiver position changes.
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    Hyperbolic-metamaterial antennas for broadband enhancement of dipole emission to free space
    (2014) Valagiannopoulos, Constantinos A.; Mirmoosa, Mohammad S.; Nefedov, Igor S.; Tretyakov, Sergei A.; Simovski, Constantin R.; Sergei Tretiakov Group; Kostantin Simovski Group; Department of Radio Science and Engineering
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    Instantaneous radiation from time-varying electric and magnetic dipoles
    (American Physical Society, 2020-07) Mirmoosa, Mohammad; Ptitcyn, Grigorii; Fleury, R.; Tretiakov, Sergei; Swiss Federal Institute of Technology Lausanne; Sergei Tretiakov Group; Department of Electronics and Nanoengineering
    Radiation from magnetic and electric dipole moments is a key subject in the theory of electrodynamics. Although people treat the problem thoroughly in the context of the frequency domain, the problem is still not well understood in the context of the time domain especially if dipole moments arbitrarily vary in time under the action of external forces. Here, we scrutinize the instantaneous power radiated by magnetic and electric dipole moments and report findings that are different from the conventional understanding of their instantaneous radiation found in textbooks. In contrast to the traditional far-field approach based on the Poynting vector, our analysis employs a near-field method based on the induced electromotive force, leading to corrective terms that are found to be consistent with time-domain numerical simulations, unlike previously reported expressions. Beyond its theoretical value, this paper may also have significant impact in the field of time-varying metamaterials especially in the study of radiation from subwavelength meta-atoms, scatterers, and emitters that are temporally modulated.
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    Multi-mode broadband power transfer through a wire medium slab
    (EMW Publishing, 2015) Vovchuk, Dmytro; Kosulnikov, Sergei; Nefedov, Igor; Tretyakov, Sergei; Simovski, Constantin; School common, ELEC; Sergei Tretiakov Group; Kostantin Simovski Group; Department of Radio Science and Engineering
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    Nihility in non-reciprocal bianisotropic media
    (EDP SCIENCES, 2015) "Ra'di", Younes; Asadchy, Viktar S.; Tretyakov, Sergei A.; Sergei Tretiakov Group; Department of Radio Science and Engineering