Effects of Dielectric Substrate on Polarization Conversion Using Coupled Metasurfaces With and Without Tunneling

Dielectric substrates are technologically necessary components of various microwave and optical structures and devices, and may strongly affect their performance. For metasurfaces composed of subwavelength resonators, placing dielectric components in the proximity of resonators can lead to strong modification of subwavelength resonances and related transmission regimes. We focus on the effects exerted by material and geometrical parameters of such a dielectric substrate on linear‐to‐linear polarization conversion that appears in quasiplanar structures containing two coupled metasurfaces and enabling chirality. It is shown that spectral locations of the polarization conversion resonances and transmission efficiency at these resonances are strongly sensitive to the substrate parameters, whereas the ability of polarization conversion and related asymmetry of transmission can be preserved in wide ranges of parameter variation. The effects of a substrate are considered in detail for the mechanisms with and without tunneling, indicating a route to compact designs of quasiplanar structures for single‐ and multiband polarization conversion

Experimental Validation of Strong Directional Selectivity in Nonsymmetric Metallic Gratings with a Subwavelength Slit

Strong directional selectivity is theoretically predicted and experimentally validated at the microwave frequencies in the beaming regime for a single subwavelength slit in nonsymmetric metallic gratings with double-side corrugations. The operation regime can be realized at a fixed angle of incidence when the surface-plasmon assisted transmission is significant within a narrow range of observation angles, if illuminating one of the grating interfaces, and tends to vanish for all observation angles, if illuminating the opposite interface. The studied effect is connected with asymmetry (nonreciprocity) in the beaming that occurs if the surface plasmon properties are substantially different for the two interfaces being well isolated from each other

Multifunctional blazed gratings for multiband spatial filtering, retroreflection, splitting, and demultiplexing based on C 2symmetric photonic crystals

The concept of multifunctional reflection-mode gratings that are based on rod-type photonic crystals (PhCs) with C 2 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.Fil: Serebryannikov, Andriy E.. Adam Mickiewicz University; PoloniaFil: Skigin, Diana Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Vandenbosch, Guy A. E.. Katholikie Universiteit Leuven; BélgicaFil: Ozbay, Ekmel. Bilkent University; Turquí

Broadband mixing of PT-symmetric and PT-broken phases in photonic heterostructures with a one-dimensional loss/gain bilayer

Combining loss and gain components in one photonic heterostructure opens a new route to efficient manipulation by radiation, transmission, absorption, and scattering of electromagnetic waves. Therefore, loss/gain structures enabling PT-symmetric and PT-broken phases for eigenvalues have extensively been studied in the last decade. In particular, translation from one phase to another, which occurs at the critical point in the two-channel structures with one-dimensionalloss/gain components, is often associated with one-way transmission. In this report, broadband mixing of the PT-symmetric and PT-broken phases for eigenvalues is theoretically demonstrated in heterostructures with four channels obtained by combining a one-dimensional loss/gain bilayer and one or two thin polarization-converting components (PCCs). The broadband phase mixing in the four-channel case is expected to yield advanced transmission and absorption regimes. Various configurations are analyzed, which are distinguished in symmetry properties and polarization conversion regime of PCCs. The conditions necessary for phase mixing are discussed. The simplest two-component configurations with broadband mixing are found, as well as the more complex three-component configurations wherein symmetric and broken sets are not yet mixed and appear in the neighbouring frequency ranges. Peculiarities of eigenvalue behaviour are considered for different permittivity ranges of loss/gain medium, i.e., from epsilon-near-zero to high-epsilon regime