Single-layer metasurface for ultra-wideband polarization conversion: bandwidth extension via Fano resonance

Abstract

In this paper, we propose a method of designing ultra-wideband single-layer metasurfaces for cross-polarization conversion, via the introduction of Fano resonances. By adding sub-branches onto the unit cell structure, the induced surface currents are disturbed, leading to coexistence of both bright and dark modes at higher frequencies. Due to the strong interaction between the two modes, Fano resonance can be produced. In this way, five resonances in all are produced by the single-layer metasurface. The first four are conventional and are generated by electric and magnetic resonances, whereas the fifth one is caused by Fano resonance, which further extends the bandwidth. A prototype was designed, fabricated and measured to verify this method. Both the simulated and measured results show that a 1:4.4 bandwidth can be achieved for both x- and y-polarized waves, with almost all polarization conversion ratio (PCR) above 90%. This method provides an effective alternative to metasurface bandwidth extension and can also be extended to higher bands such as THz and infrared frequencies.

Experimental demonstration of multiple Fano resonances appearing due to the interaction of plasmonic mode with waveguide modes in a mirrored array of split-ring resonators

“…Theoretical predictions have been con rmed experimentally on the metasurface manufactured using SSAIL technology. In comparison with 13,14 , where multiple resonances have also been observed, the proposed unit cell of the metasurface is much simpler in the present work. Moreover, the number, frequency, and amplitude of Fano resonances might be adjusted by changing the thickness of the substrate.…”

“…Theoretical considerations have shown that owing to the multimode characteristics of the slab waveguide, HMW design can offer an easy way to realize multiple Fano resonances in simple metal resonators operating in the far infrared and terahertz spectral ranges [10][11][12] . Recently in the GHz frequency range, a multiple electromagnetically induced transparency using a double-layered metasurface 13 and ultra-wideband polarization conversion extension using multiple Fano resonances 14 have been demonstrated experimentally. In both cases, to achieve multiple resonances, the unit cells of proposed metasurfaces have been rather complicated.…”

High-efficiency dual-polarized broadband reflecting metasurface using continuous polarization conversion technique and element with multi degree of freedom

“…21 ) improves the reflecting metasurface bandwidth up to 20% merely by utilizing single-layered configurations. In this regard, several works have been reported to design wideband or multi-band polarization conversion metasurfaces 22 – 26 . It can be understood that there is more freedom to manipulate the phase of reflected waves in the cross-polarization mode compared with the co-polarization (copol) one in reflective structures 19 , 21 , 27 .…”

Experimental demonstration of multiple Fano resonances in a mirrored array of split-ring resonators on a thick substrate

“…Theoretical considerations have shown that owing to the multimode characteristics of the slab waveguide, HMW design can offer an easy way to realize multiple Fano resonances in simple metal resonators operating in the far infrared and terahertz spectral ranges 10 – 12 . Recently in the GHz frequency range, a multiple electromagnetically induced transparency using a double-layered metasurface 13 and ultra-wideband polarization conversion extension using multiple Fano resonances 14 have been demonstrated experimentally. In both cases, to achieve multiple resonances, the unit cells of proposed metasurfaces have been rather complicated.…”