This paper investigates the dispersion characteristics of a highly anisotropic metamaterial comprised of metal square patches arranged in a glide-symmetry pattern and submerged in a vacuum. Theoretical formulas are proposed to describe the electromagnetic tensors of a corresponding uniaxial effective medium with dielectric and magnetic responses. In addition, this work employs theoretical analysis and numerical simulations to examine the interaction between the metamaterial and electromagnetic waves across a broad spectral range. Band diagrams and isofrequency contours show good agreement between theoretical and numerical results for low frequencies and certain directions of propagation at higher frequencies. The ease of designing the metamaterial structure for various applications is facilitated by the derived theoretical formulas, which enable accurate prediction of the electromagnetic response across a wide range of frequencies based on geometric parameters.

Plasmonic nanoantennas with constant input impedance within a wide range of mid-infrared frequencies are designed. For antennas working in lower frequencies like radiofrequencies or microwaves, it could be done by using self-complementary geometries if Babinet’s principle is approximately valid. However, the scaling up to the infrared is not trivial since metals are not good conductors in such high frequencies. We have found an alternative way to recover the validity of Babinet’s principle and thus the achievement of constant input impedance.

Efficient sensors for terahertz (THz) frequency range are in high demand for applications in biomedicine, chemistry, security, and electronics. Conventional thin-film sensing relies on spectroscopy, while improved sensitivity can be achieved using frequency selective electromagnetic metasurfaces (FSMSs). A simpler and innovative approach involves a nonspectroscopic method using a single-frequency THz source and an angle-dependent metasurface (MS) under oblique illumination. This method derives analyte parameters from the shift in the resonant transmission angle. We further develop this platform and investigate a new MS operating at 0.139 THz, exhibiting a strong variation of a narrow stopband with the angle of incidence. Theoretical, numerical, and experimental results demonstrate the MSs ability to detect submicrometer-thick films. The proposed nonspectroscopic sensing technique offers a promising avenue for highly efficient and sensitive detection of dielectric thin films.

In this work, we propose an equivalent circuit that predicts the reflectance spectra of a resonant metasurface with a pronounced variation in the resonant frequency versus the incidence angle. Two different unit-cell geometries of such a metasurface are compared, and the possibility of using both for sensing of submicron-thick films (analytes) is studied. In contrast to conventional metasurface sensors that rely on a spectral resonance shift, the angle-selective metasurface can be employed for sensing using a single-frequency THz source. The proposed circuit quantitatively predicts the reflectance spectra at different incidence angles and allows one to calculate the required angle of mechanical rotation of the metasurface that compensates for the resonance shift when a submicron analyte is deposited.

Several phenomena and applications of self-complementary metasurfaces have been studied in microwaves and sub-THz ranges like filtering, polarizing, and guiding of surface waves. However, it is rather a challenging task to scale the structures to work in mid-infrared because Babinet's principle is usually violated. We have numerically demonstrated that it is possible by using a 13 nm-thick film composed of silicon and silver.

Babinet's principle is not valid in general for plasmonic complementary metasurfaces because metals are not good conductors and sample thicknesses are not negligible respect to other tiny details of the unit cell. Nevertheless, we demonstrate that it is possible to recover its validity under a suitable choice of materials and sample thickness. Namely, we show numerical results for several complementary designs made of silicon and silver for which the validity of Babinet's principle in infrared is only confirmed when the thickness is about 13 nm.

One-dimensional waves guided along the boundary between two complementary metasurfaces have been theoretically and experimentally demonstrated in microwaves. However, it is rather a challenging task to scale down the structures to made them work in mid-infrared because Babinet's principle is usually violated. To circumvent this issue, we propose to use thin films of silicon and silver with thickness about 13 nm in which case the validity of Babinet's principle is recovered.

In this work, we investigate the possibilities of reaching wide-angle perfect absorption with Huygens' metasurfaces possessing both electric and magnetic responses. We analyze the role of the anisotropy of the polarizability tensor of the unit cell and reveal the conditions for the optimal angular stability in symmetric absorption as well as polarization independence. Then we approximate the desirable behavior with a Huygens' metasurface whose reflectance is low in a wide frequency range while the absorption is total around a single resonance frequency. Reaching of the optimal angular stability was numerically demonstrated and the corresponding wide-angle and wide-band properties were experimentally checked.

Babinet's principle is widely applied in optics and has been useful for designing metasurfaces with dual behavior. Although this principle can be rigorously demonstrated for infinitely thin perfect conducting screens, it is not exact for any real screen. In fact, metals used in plasmonic metasurfaces are far from good conductors, and the thickness of samples is not negligible in comparison with the typical size of the patterned structure. In this paper, we propose an extension of Babinet's principle valid for plasmonic metasurfaces by redefining the concept of complementary screens and finding impedance relations between such screens that ultimately leads to a simple relation between the transmission matrices of two complementary plasmonic metasurfaces. The theory is valid under the assumptions of the electroquasistatic approximation and plane waves in the far field. It may find applications in the design of optical plasmonic metasurfaces, nanocircuits, and nanoantennas.

We demonstrate and numerically characterize a set of single-layer metasurfaces based on capacitively-coupled bent metal strips deposited on a thin polypropylene film operating as band-stop filters at 139.1 GHz. Due to a high inter-digital coupling capacitance between neighboring inclusions formed by the strips, the resonance of the metasurface becomes highly sensitive to the incidence angle of a plane wave. At the same time, a narrow-band resonance is achieved by reducing the conductor length along the vertical polarization direction of the incident wave. We propose to use both properties for designing a sensor, which analyses the thickness of a thin slab of a known substance deposited over the structure by tracking the angle at which the minimum of transmission can be measured at a single frequency. We compare three versions of the proposed geometry by numerical calculation of the transmission coefficient depending on both the incidence angle and analyte slab’s thickness. We select the most suitable structure for sensing.

This article present a new approach replacing high-permittivity water-based dielectric pads with a non-resonant low-cost artificial dielectric to improve MR image quality by modifying the interferences present in the radiofrequency field at 7T MRI. The artificial dielectric comprises a stack of metal patches printed on dielectric substrates. Here we focus on the method of analytical and numerical optimization of the artificial dielectric and show that the proposed structure allows obtaining the same increase in the minimum of the transmit B-1(+) radio-frequency field distribution in a head phantom at 7 T as the conventional dielectric pad.

In this article, we theoretically and experimentally study the conversion from a circularly polarized (CP) plane electromagnetic wave into a linearly polarized (LP) transmitted one using anisotropic self-complementary metasurfaces. For this purpose, a metasurface design operable at sub-terahertz frequencies is proposed and investigated in the range of 230-540 GHz. The metasurface is composed of alternating complementary rectangular patches and apertures patterned in an aluminum layer deposited on a thin polypropylene film. Our study shows that the translational symmetry of the metasurface results in unusual and useful electromagnetic properties under illumination with CP radiation beams. In particular, alongside with broadband circular-to-linear conversion, the transmitted wave exhibits a frequency-independent magnitude, while its polarization angle gradually changes with frequency that paves the way for new beam-splitting applications.

High-permittivity dielectric pads, i.e., thin, flexible slabs, usually consisting of mixed ceramic powders and liquids, have been previously shown to increase the magnetic field at high and ultra high-fields in regions of low efficiency of transmit coils, thus improving the homogeneity of images. However, their material parameters can change with time, and some materials they contain are bio incompatible. This article presents an alternative approach replacing ceramic mixtures with a low-cost and stable artificial dielectric slab. The latter comprises a stack of capacitive grids realized using multiple printed-circuit boards. Results in this article show that the proposed artificial dielectric structure can obtain the same increase in the local transmit radiofrequency magnetic field distribution in a head phantom at 7 T as the conventional dielectric pad.

In this paper a periodic array of metal patches with glide symmetry is studied. It was found that it is a broadband uniaxial dielectric-magnetic medium with giant anisotropic factors. The transverse components of permittivity and permeability tensors are much bigger than the axial ones. Simple but accurate formulas have been provided for them.

We have implemented a method to retrieve the dispersion relation and the effective material constitutive parameters of a densely arranged periodic structure by solving an eigenvalue problem associated with the multimodal transfer matrix of the corresponding unit cell. The material parameters and the dispersion relation of a metasurface made of glide-symmetric square patches are here obtained with this method.

We numerically demonstrate a perfect metasurface absorber which reaches the closest to isotropic absorbance that can be theoretically obtained. We got total absorption at 3.18 GHz while negligible reflection for angles of incidence up to 55° or 60°. Theoretical formulas are provided for the absorbance and reflectance as functions of the incident angle.

In this work we study non-linear effects in a high permittivity artificial dielectric which results from the stacking of many parallel layers, each one made as a square net of metallic square patches. Considering the attractive electric force between induced charges and the restoring force by the host medium, we have found strong non-linear effects.

Recently self-complementary frequency-selective surfaces (FSSs) have been shown capable of linear-to-circular polarization transformation. In this work we numerically and experimentally prove generality of this approach showing that similar self-complementary tessellations can be used as FSS patterns in both the microwave and the sub-millimeter wave ranges. Moreover, we simulated two Escher's tessellations as patterns of microwave FSSs to further demonstrate the polarization transform function of arbitrary self-complementary FSSs.

We have achieved a broadband transparent metasurface useful for full phase control, conversion from linear polarization to any elliptical polarization, and anomalous refraction. Unlike other designs, our structure is made of just one type of metallic particle providing electric and magnetic resonant responses at the same frequency, instead of two types of particles each one providing each type of resonance. The unit cell of our present proposals is formed by a couple of split ring resonators. This is designed to get degeneration for the magnetic and electric resonant modes. All the designed samples are very transparent in a wide range of frequency from 0 to 6 GHz. Besides, we have numerically designed a narrowband perfect absorber with very low reflectance in a wide frequency range.

Basic properties of interaction between electromagnetic waves and self-complementary metasurfaces in recent papers are studied. Some general properties for the transmission and reflection coefficients are derived using linear and circular polarized incident waves. We show a self-complementary metasurface example made of rectangular holes and rectangular patches and the scattering parameters obtained by simulation. This geometry may be used for conversion from circular to linear polarization with any polarization angle, broadband power dividing or birefringence.