Metasurfaces for wave conversions

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2019-09-25
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Authors

Date

2019

Department

Elektroniikan ja nanotekniikan laitos
Department of Electronics and Nanoengineering

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Mcode

Degree programme

Language

en

Pages

53 + app. 55

Series

Aalto University publication series DOCTORAL DISSERTATIONS, 153/2019

Abstract

Since ancient times people were fascinated by science. In the beginning, the discoveries were a part of learning the nature phenomenon and the way the world works. Electromagnetic waves represented by the visible spectrum were one of the wonders which attracted philosophers and motivated them to learn and explore. Such wave transformations as reflection from the mirror and focusing of light into a beam by a parabolic mirror were described a long ago. Later on, more "unnatural" discoveries were made: People were trying to create structures which would behave in previously unknown ways. Could anyone imagine that at some time the scientist will be able to break the ordinary geometrical way of light reflection and re-direct it in any direction?  This dissertation is devoted to wave transformations by metasurfaces including metasurface-inspired structures. Metasurfaces are two-dimensional artificial materials created as arrangements of subwavelength inclusions. The inclusions are engineered to manipulate electromagnetic waves in the desired manner. The development of this area brings exciting opportunities to enhance known devices and to create new ones. The first part of the thesis introduces the reader into the world of two-dimensional structures developed to date and the place of metasurfaces in it (or the other way around, the place of two-dimensional structures in metasurfaces).  The second and third parts are dedicated to two types of wave manipulations in reflection regime: propagating-to-propagating waves transformation and surface-to-propagating waves conversion. The former consists of two segments. The first contains a theoretical review of propagating waves transformations using metasurfaces described by the generalized reflection law. A novel reflector antenna with a subwavelength focal distance is presented as an example of implementation of the method. The second segment introduces a novel approach to synthesis of metasurface-inspired gratings for perfect propagating wave transformation. This method allows reaching unprecedented conversion efficiency in practical realizations. The latter part at first presents a theoretical review of known structures which perform surface-to-propagating wave conversion (leaky-wave antennas) and their operation principle. Further, a novel concept for conversion with maximized efficiency is introduced for different types of propagating waves including the polarization transformation case. The results are of fundamental importance for further development and enhancement of leaky-wave antennas.

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Supervising professor

Tretyakov, Sergei, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland

Thesis advisor

Asadchy, Viktar, Dr., Stanford University, USA
Díaz-Rubio, Ana, Dr., Aalto University, Finland

Keywords

metasurfaces, metasurface-based gratings, wave transformation, wave conversion, surface wave

Other note

Parts

  • [Publication 1]: S.N. Tcvetkova, V.S. Asadchy, S.A. Tretyakov. Scanning characteristics of metamirror antennas with subwavelength focal distance, IEEE Transactions on Antennas and Propagation, 2016 vol. 64, no. 8, pp. 3656-3660,
    DOI: 10.1109/TAP.2016.2565732 View at publisher
  • [Publication 2]: V.S. Asadchy, M. Albooyeh, S.N. Tcvetkova, A. Díaz-Rubio, Y. Ra’di, S.A. Tretyakov. Perfect control of reflection and refraction using spatially dispersive metasurfaces, Physical Review B, 2016, vol. 94, no. 7, p. 075139.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201808014182
    DOI: 10.1103/PhysRevB.94.075142 View at publisher
  • [Publication 3]: S.N. Tcvetkova, D.-H. Kwon, A. Díaz-Rubio, S.A. Tretyakov. Near-perfect conversion of a propagating plane wave into a surface wave using metasurfaces, Physical Review B, 2018, vol. 97, no. 11, p. 115447.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201805222249
    DOI: 10.1103/PhysRevB.97.115447 View at publisher
  • [Publication 4]: S.N. Tcvetkova, S. Maci, S.A. Tretyakov. Exact solution for conversion of surface waves to space waves by periodical impenetrable metasurfaces, IEEE Transactions on Antennas and Propagation, 2019, vol. 67, no. 5, pp. 3200-3207,
    DOI: 10.1109/TAP.2019.2896765 View at publisher
  • [Publication 5]: S.N. Tcvetkova, S.A. Tretyakov, S. Maci. Perfect conversion from surface wave to leaky wave through periodic metasurfaces, 13th European Conference on Antennas and Propagation (EuCAP 2019), pp. 2458-2460.

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https://urn.fi/URN:ISBN:978-952-60-8691-0

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[diss] Sähkötekniikan korkeakoulu / ELEC