We propose a novel design of a true 3D chiral metasurface behaving as a spatial polarization converter with asymmetric transmission. The metasurface is made of a lattice of metallic sesquialteral (one and a half pitch) helical particles. Each particle contains six rectangular bars arranged in a series one above the another creating a spiral. The proposed metasurface exhibits a dual-band asymmetric transmission accompanied by the effect of a complete polarization conversion in the response on the particular distributions of currents induced in the particle's bars by an incident wave. Regarding circularly polarized waves the metasurface demonstrates a strong circular dichroism. A prototype of the metasurface is manufactured for the microwave experiment by using 3D-printing technique utilizing Cobalt-Chromium alloy, which exhibits good performances against thermal fatigue and corrosion at high temperatures. Our work paves the way to find an industrial solution on fabricating communication components with efficient polarization conversion for extreme environments.

A numerical method in the frequency domain is developed for analyzing three-dimensional gratings using the concept of a double-periodic magnetodielectric layer. The method is based on the three-dimensional volume integral equations for the equivalent electric and magnetic polarization currents of the assumed periodic medium. The integral equations are solved by using the integral functionals related to the polarization current distributions and the technique of double Floquet-Fourier series expansion. Once the integral functionals are determined, the scattered fields outside the layer are calculated accordingly. The unit cell of the layer comprises several parallelepiped segments of materials characterized by the complex-valued relative permittivity and permeability of step function profiles. The arbitrary profiles of three-dimensional dielectric or metallic gratings can be flexibly modeled by adjusting the material parameters and sizes or locations of the parallelepiped segments in the unit cell. Numerical examples for various grating geometries and their comparisons with those presented in the literature demonstrate the accuracy and usefulness of the proposed method.

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Transmission of linearly and circularly polarized waves is studied both theoretically and experimentally for chiral metasurface formed by an array of metallic square helices. The helical particles of the metasurface are constructed of rectangular bars manufactured with the use of direct 3D printing in solid metal. It is found that transmittance of the metasurface depends critically on number of bars forming the square helical particles. In the case of even number of bars, chiral metasurface exhibits the identical co-polarized transmittance of orthogonal linearly polarized waves, which are characterized by a dual-band asymmetric transmission. In the case of odd number of bars, the metasurface provides the same crosspolarization conversion for any polarization orientation of the incident field and thus serves as a polarization-independent twist polarizer. Transmittance of this polarizer is investigated with respect to the dimensions of square helices. It is shown that chiral metasurface under investigation is characterized by strong broadband circular dichroism without regard to the number of bars used in the helical particles. A wide variety of transmission properties of such a metasurface makes it particularly attractive for use in polarization conversion and separation devices.

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We report on a new class of mechanically tunable planar metamaterials comprising resonating units formed by crossed metallic strip gratings. We observe a resonant response in transmission spectra of a linearly polarized wave passing through the system of crossed gratings. Each grating consists of an array of parallel metallic strips located on the top of a dielectric substrate. It is revealed that the resonant position appears to be dependent on the angle of gratings crossing. It is found out both theoretically and experimentally that the resonant shift on the frequency scale appears as a result of increasing in the length of the resonating portion of the parallelogram periodic cell formed by the crossed metallic strips with decreasing crossing angle and the proposed design can be used in new types of planar metamaterials and filters.In recent decades, a huge number of publications appeared which are related to the study of the optical properties of metamaterials. Metamaterials are composites possessing characteristics that cannot be found in nature (see, for instance, [1,2] and references therein). In such artificial systems the unit cell serves as an atom or molecule in conventional natural materials, whereas it can be adjustable through varying cell's geometry and constituents. Those of them that are produced by planar technology remains among the most promising for applications. They are also known as metasurfaces [3,4].Typically metasurfaces manifest a resonant response due to excitation of the magnetic and/or electric modes. This resonant response of metasurfaces is a cornerstone for achieving exotic behaviors which are dependent on the composition and structure of the structures' unit cell [5,6].

In this Letter, a completely ferrodielectric metasurface consisting of an array of cylinders on a substrate is studied. All structural elements are made of ferrodielectric material. The conditions for the excitation of Wood’s anomaly mode, obtained for different geometric parameters of the metasurface, are revealed. By continuously changing the structure parameters, we can change the position of the resonance at the Wood anomaly, thereby setting the position of the resonance at the frequency we need. It is shown that there is a resonant increase in the polarization plane rotation of the transmitted waves at the corresponding resonant frequency of the lattice mode excitation. Such polarization rotation is demonstrated both experimentally and theoretically.