A Fishnet Metasurface as an Ultra-Thin Quarter Wave Plate

Authors A.O. Perov

O.Ya. Usikov Institute for Radiophysics and Electronics NASU, 12, Akad. Proskura St., 61085 Kharkiv, Ukraine

Е-mail andrii.perov@gmail.com
Issue Volume 13, Year 2021, Number 5
Dates Received 16 September 2020; revised manuscript received 20 October 2021; published online 25 October 2021
Citation A.O. Perov, J. Nano- Electron. Phys. 13 No 5, 05005 (2021)
DOI https://doi.org/10.21272/jnep.13(5).05005
PACS Number(s) 41.20. – q, 42.25.Bs, 42.25.Ja
Keywords Polarization conversion, Quarter-wave plate, Subwavelength holes, Metasurface.

In the paper, a design of an ultra-thin quarter wave plate using a fishnet metasurface is described. The metasurface is arranged as a periodic array of compound supercells with subwavelength circular holes. Even though the holes are polarization insensitive, it is shown that one can control polarization response manipulating with metasurface supercell asymmetry. A specific phase difference between the x and y components of the transmitted field can be obtained by manipulating with hole locations in the supercell as well as with periodic supercell dimensions. In the design, magnitude and phase of two orthogonal components for the transmitted field can be controlled independently, hence enabling efficient and robust polarization conversion. It is explained that the effect of conversion of a linearly polarized wave into a circularly polarized one is due to enhanced transmission phenomenon through subwavelength holes and coupling with orthogonal eigenmodes of the metasurface. In the case of subwavelength holes, a whole periodic supercell behaves as a scatterer, which combines impacts of the individual elements leading to the strong polarization sensitivity, which cannot be observed in the case of resonant ones. It is analytically shown that the effect of polarization conversion for ultra-thin metasurfaces appears when two orthogonal eigenmodes with closely spaced eigenfrequencies are coupled to the incident field. Analytical formulas to describe the polarization effects as a function of eigenfrequencies are obtained, and the conditions to get the maximum level of the conversion efficiency possible for ultra-thin single layer structures are discussed.

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