Browsing by Author "Serebryannikov, Andriy E."
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Item Few‑layer bifunctional metasurfaces enabling asymmetric and symmetric polarization‑plane rotation at the subwavelength scale(Springer Nature, 2024-06-13) Gokkavas, Mutlu; Gundogdu, T. F.; Ozbay, Ekmel; Serebryannikov, Andriy E.We introduce and numerically validate the concept of few‑layer bifunctional metasurfaces comprising two arrays of quasiplanar subwavelength resonators and a middle grid (array of rectangular holes) that offer both symmetric and asymmetric transmissions connected, respectively, with symmetric and asymmetric polarization‑plane rotation functionalities. The proposed structures are thinner than lambda/7 and free of diffractions. Usually, the structure’s symmetry or asymmetry, i.e. unbroken or broken spatial inversion symmetries, are considered for metasurfaces as prerequisites of the capability of symmetric or asymmetric conversion of linearly polarized waves, respectively. Due to the achieved adjustment of the resonances enabling the rotation of the polarization plane simultaneously for both orthogonal polarizations of the incident wave, the symmetric polarization‑plane rotation functionality can be obtained within one subwavelength band, whereas the asymmetric polarization‑plane rotation functionality associated with the asymmetric transmission is obtained within another subwavelength band. This combination of the functionalities in one subdiffraction structure is possible due to the optimal choice of the grid parameters, since they may strongly affect the coupling between the two resonator arrays. Although normal incidence is required for the targeted bifunctionality, the variations of the incidence angle can also be exploited for the enrichment of the overall functional capability. Variations of the polarization angle give another important degree of freedom. The connection between the polarization‑angle dependence of cross‑polarized transmission and capability of symmetric and asymmetric polarization‑plane rotation functionalities is highlighted. The feasible designs of the bifunctional metasurfaces are discussed.Item Multifunctional Blazed Gratings for Multiband Spatial Filtering, Retroreflection, Splitting, and Demultiplexing Based on C2 Symmetric Photonic Crystals(American Institute of Physics, 2022-06-08) Serebryannikov, Andriy E.; Skigin, Diana C.; Vandenbosch, Guy A. E.; Ozbay, EkmelThe concept of multifunctional reflection-mode gratings that are based on rod-type photonic crystals (PhCs) with C2 symmetry is introduced. The specific modal properties lead to the vanishing dependence of the first-negative-order maximum on the angle of incidence and the nearly sinusoidal redistribution of the incident-wave energy between zero order (specular reflection) and first negative diffraction order (deflection) at frequency variation. These features are key enablers of diverse functionalities and the merging of different functionalities into one structure. The elementary functionalities, of which multifunctional scenarios can be designed, include but are not restricted to multiband spatial filtering, multiband splitting, retroreflection, and demultiplexing. The proposed structures are capable of multifunctional operation in the case of a single polychromatic incident wave or multiple mono-/polychromatic waves incident at different angles. The generalized demultiplexing is possible in the case of several polychromatic waves. The aforementioned deflection properties yield merging demultiplexing with splitting in one functionality. In turn, it may contribute to more complex multifunctional scenarios. Finally, the proposed PhC gratings are studied in transmissive configuration, in which they show some unusual properties.Item Thermally switchable, bifunctional, scalable, mid infrared metasurfaces with VO2 grids capable in versatile polarization manipulation and asymmetric transmission(Optica (formely OSA), 2022-11-16) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Ozbay, EkmelWe conceptualized three-array scalable bifunctional metasurfaces comprising only three thin strip grids and numerically determined their characteristics in the mid-infrared spectral regime for switchable operation scenarios involving polarization manipulation and related diodelike asymmetric transmission (AT) as one of two functionalities. A few or all of the grids were taken to be made of VO2, a bifunctionality-enabling phase-change material, there are no layers and/or meta-atoms comprising simultaneously both metal and VO2. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO2. The achieved scenarios of functionality switching significantly depend in the way in which VO2 is incorporated in the metasurface. Switchable bands of polarization manipulation are up to 40 THz wide. The AT band can be modulated when Fabry–Perot (anti-) resonances come into play. Besides, transmission regimes with the cross-polarized component insensitive to VO2 phase change are possible, as well as the ones with co- and cross-polarized components having the same magnitude for the both linear polarizations of the incident wave.