This work has developed and simulated a planar complementary Archimedes-based metamaterial absorber with the goal of its application in refractive index sensing. Unlike designs that employ multiple layers or numerous resonators within a single unit cell, our proposed absorber adopts a more streamlined approach. It consists of three layers, with an FR4 dielectric substrate sandwiched between two copper layers. It's important to note that the absorption characteristics of this design are polarization-dependent. This polarization dependence arises from the asymmetrical resonance behavior observed in both the x and y directions. The absorber exhibits impressive absorption rates at various resonance frequencies, namely 98.5% at f₁ = 8.49 GHz, 77.1% at f₂ = 8.88 GHz, 88.7% at f₃ = 9.3 GHz, 98.2% at f₄ = 9.87 GHz, 99.7% at f₅ = 10.65 GHz, 83.4% at f₆ = 11.58 GHz, and 99.9% at f₇ = 12.24 GHz. Furthermore, the article explored the refractive index sensing capabilities of this structure by introducing a 1 mm analyte layer on top of the patch structure. Through refractive index sensing analysis, we've determined that this absorber-based sensor yields an impressive high-quality factor value of 84.5, highlighting its remarkable sensitivity and precision. A more profound comprehension of the physical mechanisms in action has been attained by examining the distribution of surface currents. Furthermore, the behavior of the absorber has been investigated under varying polarization and incident angle conditions, ranging from zero degrees to sixty degrees. The thorough characterization establishes this absorber as a promising choice for microwave sensing applications.

This study proposes a five-band perfect metamaterials absorber (MMA) for 5G communication in the K- and Ka-bands of the microwave range. The MMA design is based on a folded arms resonator (FAR) with a novel shape, forming the fundamental unit of the absorber. This absorber demonstrates a reasonably wide range of absorption capabilities for 5G communication in the K and Ka bands of the microwave region. The absorptivity of the MMA was examined for both normal and oblique incidence of waves in the frequency range of 20–26 GHz. According to a theoretical analysis, five absorption peaks at resonance frequencies of 20.38, 21.75, 23.1, 24.22 and 25.12 GHz exhibit absorption rates of 97.8%, 92.9%, 97.2%, 99.3% and 96.8%, respectively. The overall average absorption rate is 95.53%, taking into account the presence of two perfect absorption peaks. By adjusting the structural parameters, it is possible to influence the absorption peaks and resonant wavelengths. Additionally, the absorber demonstrates a high level of symmetry, resulting in insensitivity to TE mode polarisation angle and incident angle. The fractal resonators exhibited a capacitive effect at lower frequencies, while the SRRs demonstrated a capacitive effect at higher frequencies. This MMA design is expected to have practical applications in 5G communication technology.

In this work, a triple-band polarization-insensitive metamaterial structure with perfect absorption is proposed by incorporating a zinc selenide (ZnSe) spacer. The structure was optimally designed by varying the type of the spacer and the unit cell dimensions. The structure was simulated using the finite integration technique, and the results showed that the proposed design achieved a near-perfect absorption of about 99%, 99%, and 100% at 22.50, 28.98, and 35.14 THz, respectively. Its absorption characteristics were insensitive to the polarization angle and a wide range of incidence angles, making it an ideal absorber. Further investigations of the electric field, magnetic field, and surface current distributions were carried out to elaborate on the absorption characteristics at various resonance frequencies. The proposed device can also be used as a sensor that can detect the depth of the surrounding analyte and its refractive index. The device could detect the depth of the analyte with a peak sensitivity of 2.76 THz μ m ⁻¹ and its refractive index with a peak sensitivity of 1.55 THz RIU ⁻¹ . Thus, the design could have interesting terahertz applications.

In this study, almost monochromatic tuning of absorption strength, i.e. tuning the absorption peak level at almost same frequency, is presented by using angle dependent closed ring resonator (AD-CRR) type narrow band absorber structure in S-band. On this aim, firstly an ordinary planar closed ring resonator (CRR) structure having ground plane is designed and then the structure is folded by a rotation angle α from α = 0° (i.e. planar CRR) to α = 90° (i.e. completely folded CRR) along the center line which is parallel to the incident electric field. Both simulation and experimental results agree that the rotation angle α provides the freedom of tuning the absorption strength of the absorber structure almost monochromatically.