An oblique angle and polarization insensitive metamaterial absorber (MA) are highly desired for the visible and infrared optical applications like, wave energy harvesting, optical filters, and detecting thermal leaks and electrical defects. In this paper, a multi-layered MA consisting of two layers of tungsten resonators on a silicon dioxide substrate, coated with additional SiO₂ materials is investigated. The unit cell size of the MA is 0.5λ × 0.5λ × 0.8λ, at the lowest wavelength. The proposed MA offers an average absorption of 92% from 400 nm to 2400 nm with stable oblique incident angles up to 45°. The structure also achieves polarization insensitivity at the entire visible and near-infrared spectrum. Moreover, the MA is found highly compatible for solar absorber applications with high y A_AM1.5. The structure is also compatible for filter application in optical communication system by modifying the plasmonic nano structure. The modified structure can block the wavelengths of the visible band (450 nm to 800 nm) and transmit optical communication bands (800 to 1675 nm). These versatile absorption and filtering performance make the proposed design highly potential for solar energy harvesting, photodetection, thermal imaging, photo-trapping, and optical communications applications.

The visible and infrared wavelengths are the most frequently used electromagnetic (EM) waves in the frequency spectrum; able to penetrate the atmosphere and reach Earth’s surface. These wavelengths have attracted much attention in solar energy harvesting; thermography; and infrared imaging applications for the detection of electrical failures; faults; or thermal leakage hot spots and inspection of tapped live energized components. This paper presents a numerical analysis of a compact cubic cross-shaped four-layer metamaterial absorber (MA) structure by using a simple metal-dielectric-metal-dielectric configuration for wideband visible and infrared applications. The proposed MA achieved above 80% absorption in both visible and near-infrared regions of the spectrum from 350 to 1250 nm wavelength with an overall unit cell size of 0.57λ × 0.57λ × 0.59λ. The SiO₂ based anti-reflection coating of sandwiched tungsten facilitates to achieve the wide high absorption bandwidth. The perceptible novelty of the proposed metamaterial is to achieve an average absorptivity of 95.3% for both visible and infrared wavelengths with a maximum absorptivity of 98% from 400 nm to 900 nm. Furthermore, the proposed structure provides polarization insensitivity with a higher oblique incidence angle tolerance up to 45°.

In This paper Square Split Enclosed Labyrinth Maze Shaped structured metamaterial absorber (MMA) has been proposed for Hydrocarbon Sensing Application. The three-layered MMA design has an FR-4 substrate layer laminated copper and a resonating layer of concentric continuous and split rings. This MMA works together S-band and Ku band. Various parameters have been studied to understand the absorption characteristics of the MMA including reflection coefficient, magnetic fields, electric fields, surface currents. The MMA has an absorbance of 99.4% from 2.44 GHz - 3.57 GHz and an absorbance of 91.65%. Also, the proposed MMA sensor provides higher sensitivity in detecting different hydrocarbon by detecting the permittivity changes of the test objects Also, The MMA sensor setup had a peak reflection band at 11.28 GHz. The lowest band shift is 0.01 GHz between Heptane and Octane. That the average sensitivity of the MMA is 1.4 GHz/ε for different Hydrocarbon materials. The high absorbance makes this MMA suitable for various microwave applications, including hydrocarbon sensing applications.

This article presents a highly sensitive Modified Hilbert resonator-based transmission line sensor for moisture level estimation of soil. The Hilbert Resonator (HR) sensor offers significant advantages over traditional moisture sensors, as it can remotely respond to different soil moisture levels and enables the detection of even small changes in moisture levels. The sensor’s sensitivity is quantified at 82 (MHz/pp), indicating its ability to detect moisture fluctuations in different soil samples. Experiments were conducted using three soil samples with varying moisture levels, from dry to 20%. The sensor exhibited measurable linear fluctuations in transmitted signals between 4.5 and 6 GHz for all soil samples. These findings demonstrate the sensor’s potential for improved soil management and agricultural practices, making it a promising tool for remote soil moisture-sensing applications. The results highlight the significance of the modified Hilbert resonator-based transmission line sensor in contributing to sustainable resource management and enhanced productivity across various domains.

This study introduces a novel metamaterial (MTM)-inspired sensor architecture employing four split-square resonators (SSRs). The sensor’s design integrates microstrip technology and incorporates four RF resonators of varying sizes, generating distinct resonant frequencies with a higher quality factor. These RF resonators are fabricated on a Rogers RT5880 substrate characterized by a dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 1.6 mm. The sensor configuration comprises four SSRs; each resonator resonates at its unique frequency. Overall, the sensor resonates at the frequencies of 3.36, 3.66, 4.26, and 4.69 GHz. When a liquid flow containing insoluble particles is directed onto any of the SSRs, the resonant frequency of the respective SSR undergoes a shift from its baseline position due to variations in dielectric properties. In this study, purified Palm oil (with a dielectric value, $\varepsilon _{\text {oil}}$ , of 2.8) serves as the flowing liquid, while distilled water ( $\varepsilon _{w} =78$ ) and regular air ( $\varepsilon _{a} =1$ ) are employed as insoluble particles. Notably, the resonant frequency demonstrates high sensitivity to changes in the dielectric value within the capacitive region of the SSRs. The avaseg sensitivity of the sensor is 0.75 GHz/ $\varepsilon $ for air sample and 0.025 GHz/ $\varepsilon $ for water sample. To validate the sensor’s operational principles, a comparative analysis between simulated and measured transmission results has been conducted. Furthermore, five distinct predictive machine learning (ML) classification algorithms were employed and compared to mitigate errors arising from environmental factors, such as fluctuations in oil properties. The decision tree model achieved an average of 99.25% accuracy.

This article proposed a square splits ring resonator for K band application. the proposed absorber simulated for both transverse magnetic (TM) mode and transverse electric (TE) mode. The FR-4 substrate material is used with dielectric constant 4.3 and thickness 1.6 mm. the overall dimension of the absorber is 13.5x13.5 mm2, at TE mode 530 MHz 90% achieved from 22.2 GHz-22.73 GHz and at TM mode 400MHz 90 % bandwidth achieved from 23.5-23.9 GHz. The unit cell boundary condition is applying for both types of simulation. The e-field, h-field, and surface current for both TE and TM mode have been presented and a comparison is done with resent metamaterial absorber