Pseudo-anapole regime in terahertz metasurfaces

Maria V. Cojocari, Anar K. Ospanova, Vladimir I. Chichkov, Miguel Navarro-Cia, Andrei Gorodetsky, Alexey A. Basharin

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We present the numerical, theoretical, and experimental study of a terahertz metasurface supporting a pseudo-anapole. Pseudo-anapole effect arises when electric and toroidal dipole moments both tend to a minimum, instead of destructive interference between electric and toroidal dipole moments in conventional anapole mode. Such overlap allows resonance suppression of electric type radiation. Thus, it becomes possible to study the multipoles of other families and higher order excitations. We estimate multipoles contribution to the metasurface response via the multipole expansion method. The series is extended with such terms as mean-square radii and multipoles interference. We also study the metasurface geometrical tunability. Via scaling, we demonstrate that it is possible to control the metasurface toroidal and electric responses independently. This in turn proves the fact that these multipoles have different physical origin. Moreover, we demonstrate that proposed metasurface allows excitation of coherent magnetic dipole and electric quadrupole modes which is crucial for planar cavities and lasing spasers in nanophotonics.
Original languageEnglish
Article number075408
Pages (from-to)1-8
Number of pages8
JournalPhysical Review B
Issue number7
Publication statusPublished - 5 Aug 2021

Bibliographical note

Funding information: A.G. acknowledges support from Russian Foundation
for Basic Research (Grant No. 18-07-01492-a) and EPSRC (Grant No. EP/S018395/1). A.K.O. acknowledges support from RSF (Grant No. 20-72-00016) for multipole decomposition analysis works. M.N.-C. acknowledges support from the Royal Society (Grant No. IEC/NSFC/191104), EPSRC (Grant No. EP/S018395/1), and the European Union Horizon 2020 research and innovation programme (Grant No. 777714). V.I.C. acknowledges the Ministry of Science and Higher Education of the Russian Federation (Project No. 0718-2020-0025) for support of sample fabrication. A.A.B. acknowledges the RSF (Project No. 21-19-00138) for support of simulations, MISiS team acknowledge support from the Ministry of Education (Grant No. K2-2018-015). A.G. thanks Magicplot LLC for providing a copy of MagicPlot Pro plotting and fitting software used for preparation of all figures in the manuscript.


  • anapole
  • metasurface
  • multipole expansion
  • terahertz
  • time-domain spectroscopy


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