Search Results (304)

Augmented reality (AR) near-eye displays (NEDs) couple microdisplay image light to the human eye via integrated optical modules, enabling seamless virtual–real fusion. As core components that synergistically transmit and diffract light, diffractive waveguides are promising for next-generation AR NEDs but face two bottlenecks: compromised full-color performance in single-layer structures caused by grating dispersion and lack of scalable fabrication technologies. To address these, we first propose a mass-production-compatible workflow based on deep ultraviolet (DUV) lithography for large-area nanostructured optics. This workflow enables high-precision wafer-level production with 200 mm wafers and nine dies per wafer, overcomes scalability issues, and is fully compatible with straight-configuration nanostructures to ensure manufacturing feasibility. Leveraging this workflow, we develop a single-layer diffractive waveguide system for AR NEDs, which comprises a thin glass substrate, a broadband high-efficiency multi-layer dielectric in-coupler, and a 2D out-coupler that concurrently expands and out-couples light. Rigorous coupled wave analysis (RCWA) optimized coupler diffraction, while ray tracing refined guided light intensity and significantly improved exit pupil uniformity. This work establishes a foundation for full-color, high-efficiency AR waveguides and provides a scalable paradigm for large-area nanostructured optical systems such as telescopes and lithography equipment. Full article

This work focuses on developing resistive switching (RS) devices using thermally annealed (TA) SiO₂/Si multilayers (ML). Three SiO₂/Si bilayers were deposited with an additional 10 nm SiO₂ layer as a dielectric barrier layer on top of the ML. The SiO₂ layers were 6 nm thick, while the thickness of the Si layers varied from 2, 4, and 6 nm, and were labeled as ML-62, ML-64, and ML-66, respectively. X-ray photoelectron spectroscopy analysis revealed well-defined ML structures before TA. However, after TA, samples ML-64 and ML-62 showed discontinuities due to diffusion between neighboring Si layers, increasing the dimensions of the Si-rich regions. In fact, the concentration of elemental Si (Si⁰) within the intermediate Si layer increases as the Si layer becomes thinner. Consequently, the size of Si-nanocrystals, created after TA, increases from 6 to 8.5 nm for ML-66 to ML-62, as confirmed by Raman and transmission electron microscopy analysis. The composition discontinuities and loss of the ML structure resulted in erratic electrical behavior, with an electroforming (EF) voltage as high as −14 V in sample ML-62. For the ML-66, which retained the ML structure, the EF voltage was reduced to −4 V, showing SET/RESET values of around ±3 V and stable electrical behavior, with an ON/OFF ratio of up to seven orders of magnitude. This demonstrates the importance of the ML design in the operation of RS devices. Full article

The present work systematically investigates the impact of multilayer architecture—specifically 5, 10, and 15 layers—on the structural, morphological, optical, and dielectric properties of zinc oxide (ZnO) thin films, aiming to tailor their characteristics for optoelectronic applications. The films were characterized using a comprehensive suite of techniques. X-ray diffraction (XRD) analysis of the 15-layer sample confirmed the formation of polycrystalline ZnO with a hexagonal wurtzite crystal structure, showing prominent (100), (002), and (101) diffraction peaks. Measurements indicated that the film thickness progressively increased from 43.81 nm for 5 layers to 80.68 nm for 15 layers. Concurrently, the surface roughness significantly decreased from 5.54 nm (5 layers) to 2.00 nm (15 layers) with increasing layer count, suggesting enhanced film quality and densification. Optical studies using ultraviolet–visible (UV-Vis) spectroscopy revealed an increase in absorbance and a corresponding decrease in transmittance in the UV-Vis spectrum as the film thickness increased. The calculated optical band gap showed a slight redshift, decreasing from 3.26 eV for the 5-layer film to 3.23 eV for the 15-layer film. Photoluminescence (PL) spectra exhibited characteristic near-band-edge UV emission, with the 5-layer film demonstrating the highest PL intensity. Furthermore, analysis of optical constants revealed that the refractive index, extinction coefficient, optical conductivity, and both the real and imaginary parts of the dielectric constant generally increased with an increasing number of layers, particularly in the visible region, while more nuanced and non-monotonic trends were observed in the UV range. These results underscore the significant influence of layer number on the physical properties of ZnO thin films, providing valuable insights for optimizing their performance in various optoelectronic devices. Full article

Dielectric/Ag/dielectric (DAD) multilayer thin-film transparent electrode features high visible-light transmittance, low sheet resistance, good mechanical flexibility, and low haze. The fabrication techniques are compatible with large-scale integrated circuits, and the materials are cheap. These advantages make the DAD transparent electrodes a promising alternative to indium tin oxide (ITO) electrodes for flexible devices. This review summarizes recent advances in DAD transparent electrodes on flexible substrates, mainly focusing on the opto-electrical performance improvement due to damping of the localized surface resonance (LSPR) of Ag nanoparticles (AgNPs). It begins with an analysis of the performance-limiting factors of DAD transparent electrodes, elucidating the importance of damping the LSPR of AgNPs. Subsequently, the state-of-the-art fabrication methods for Ag ultrathin films of weak LSPR and the dielectric material optimization are reviewed. It concludes with perspectives on future research. Full article

Anemia caused by gastrointestinal parasitism is a major constraint to small ruminant productivity, particularly in low-resource production systems where diagnostic tools and veterinary access are limited, with use of FAMACHA as a biological reference This study evaluated the potential of radio-frequency non-destructive technique (RF-NDT) wave-derived features as non-invasive biomarkers for anemia detection in goats, using FAMACHA© scores as a biological reference. Variable clustering of the top ten frequencies revealed distinct patterns across health states. Healthy (FAMACHA© 1) animals were characterized by a single frequency cluster centered at 8.43 GHz, which explained 93.7% of variation, whereas moderately affected animals (FAMACHA© 2) shifted to 9.33 GHz with reduced uniformity (88.7%). Borderline animals (FAMACHA© 3) required two clusters (9.89 and 8.23 GHz), explaining 91.0% of variation, indicating increasing tissue heterogeneity with anemia progression. Regression analysis demonstrated strong predictive power, with Linear Regression achieving R² = 1.00 and Random Forest R² = 0.79 (RMSE = 0.07), Support Vector Regression underperformed (R² = 0.31). Classification models confirmed the feasibility of categorical anemia detection. The Multilayer Perceptron achieved the highest accuracy (0.84), F1-score (0.83), and ROC-AUC (0.94), outperforming Support Vector Machine (accuracy 0.67, F1 = 0.67) and K-Nearest Neighbors (accuracy 0.60, F1 = 0.61). These findings establish proof-of-concept that RF waves capture physiologically meaningful dielectric signatures linked to anemia, reflecting hemoglobin concentration, hydration, and microcirculatory function. The integration of RF sensing with machine learning offers a rapid, and non-invasive scalable diagnostic approach. Future work should expand validation across breeds and environments, optimize sensor design, and embed neural classifiers for field-ready deployment. Full article

This paper introduces a novel design of a circularly polarized (CP) beamforming antenna that is capable of shaping the original beam into a flat-top configuration. Upon loading a metallic ring, the beamforming pattern can transition into an isoflux pattern. The proposed compact lens antenna comprises a multi-layer honeycomb-like unit lens structure, with a patch and support platform situated beneath the lens. Positioned above the lens, a loadable metallic ring is employed to assist in beamforming. Through a specially designed dielectric lens structure, the lens can control the radiation of electromagnetic waves to achieve the desired beam pattern, while the loadable metallic ring plays a role in optimizing the field across the aperture plane of the lens. This work utilizes a multi-port feed network to drive the patch. To validate the proposed antenna design method, a prototype is fabricated for measurement. The measured result is nearly identical to the simulated result. Within the frequency range spanning from 4.8 GHz to 5.2 GHz (which represents a 10% bandwidth), the antenna demonstrates effective beamforming ability and achieves effective pattern switching. This renders it a promising candidate for scenarios where uniform signal strength coverage is required. Full article

The proliferation of wireless networking solutions, which are omnipresent in our daily lives, has led to increased exposure to the energy of electromagnetic (EM) waves in the higher frequency range, raising concerns about their impact on human health. Investigating the propagation of EM waves through multilayer structures can shed light on the future direction of effective protection and shielding solutions. The paper provides a comparative study that examines EM wave propagation through a multilayered composite structure. The structure combines Plexiglas plates (acrylic, polymethyl methacrylate), a dielectric material, with one or more layers of conductive YSHIELD HSF54 paint to reduce EM field intensity. The paint’s carbon-based particle composition promises effective field attenuation. Our side-by-side comparative real-world measurements and simulation results showcase correlation. We further demonstrated the benefits of applying a layer of conductive YSHIELD HSF54 paint over Plexiglass to form a composite structure, with the initial layer contributing to attenuation of approximately 20 dB. Finally, the results were validated by calculating Morozov’s first- and second-order analytical approximations for the transmission parameter $S_{21}$—the calculated values accurately trace both the simulations and measurements. The research concludes that shielding, which is used as a method of protection against EM radiation in many industrial devices, can also be used in procedures to protect human habitats by selecting new, innovative, and affordable materials and structures. Full article

Plasmonic metasurfaces that convert hydrogen-induced dielectric changes into optical signals hold promise for next-generation hydrogen sensors. Here, we employ simulations and theoretical analysis to systematically assess single-layer, bilayer, and trilayer nanodisk arrays comprising magnesium, palladium, and noble metals. Although monolithic Mg nanodisks show strong optical contrast after hydrogenation, the corresponding surface plasmon resonance disappears completely, preventing quantitative spectral tracking. In contrast, bilayer heterostructures, particularly those combining Mg and Au, achieve a resonance red-shift of Δλ = 62 nm, a narrowed full width at half maximum (FWHM) of 207 nm, and a figure of merit (FoM) of 0.30. Notably, the FoM is boosted by up to 15-fold when tuning both material choice and stacking sequence (from Mg-Ag to Au-Mg), underscoring the critical role of interface engineering. Trilayer “sandwich” architectures further amplify performance, achieving a max 10-fold and 13-fold enhancement in Δλ and FoM, respectively, relative to its bilayer counterpart. Particularly, the trilayer Mg-Au-Mg reaches Δλ = 120 nm and FoM = 0.41, outperforming most previous plasmonic hydrogen sensors. These enhancements arise from maximized electric-field overlap with dynamically changing dielectric regions at noble-metal–hydride interfaces, as confirmed by first-order perturbation theory. These results indicate that multilayer designs combining Mg and noble metals can simultaneously maximize hydrogen-induced spectral shifts and signal quality, providing a practical pathway toward high-performance all-optical hydrogen sensors. Full article

Reliable DC cable insulation is crucial for photovoltaic (PV) systems and high-voltage DC (HVDC) networks. However, conventional materials such as cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC) face challenges under prolonged DC stress—notably space charge buildup, dielectric losses, and thermal aging. Cross-linked polyolefin (XLPO) has emerged as a halogen-free, thermally stable alternative, but its comparative DC performance remains underreported. Methods: We evaluated the insulations of virgin XLPO, XLPE, and PVC PV cables under ±1 kV DC using time-domain indices (IR, DAR, PI, Loss Index), supported by MATLAB and FTIR. Multi-layer cable geometries were modeled in MATLAB to simulate radial electric field distribution, and Fourier-transform infrared (FTIR) spectroscopy was employed to reveal polymer chemistry and functional groups. Results: XLPO exhibited an IR on the order of 10⁸–10⁹ Ω, and XLPE (IR ~ 10⁸ Ω) and PVC (IR ~ 10⁷ Ω, LI ≥ 1) at 60 s, with favorable polarization indices under both polarities. Notably, they showed high insulation resistance and low-to-moderate loss indices (≈1.3–1.5) under both polarities, indicating controlled relaxation with limited conduction contribution. XLPE showed good initial insulation resistance but revealed polarity-dependent relaxation and higher loss (especially under positive bias) due to trap-forming cross-linking byproducts. PVC had the lowest resistance (GΩ-range) and near-unit DAR/PI, dominated by leakage conduction and dielectric losses. Simulations confirmed a uniform electric field in XLPO insulation with no polarity asymmetry, while FTIR spectra linked XLPO’s low polarity and PVC’s chlorine content to their electrical behavior. Conclusions: XLPO outperforms XLPE and PVC in resisting DC leakage, charge trapping, and thermal stress, underscoring its suitability for long-term PV and HVDC applications. This study provides a comprehensive structure–property understanding to guide the selection of advanced, polarity-resilient cable insulation materials. Full article

A ceramic-based wideband capacitive-fed patch-loaded multi-layered rectangular dielectric resonator antenna (CFPL-ML-RDRA) with a compact form factor is proposed in this paper. The proposed antenna is composed of two ceramic substrates and a polymer as an adhesive. A capacitive-fed metallic patch structure is located on the top side of the bottom ceramic substrate. This novel structure generates two distinct resonant modes: the fundamental resonant mode of the RDRA and a hybrid resonant mode, which was confirmed through electric field (E-field) analysis and parametric studies. By merging these two resonant modes, the proposed antenna achieves a wide impedance bandwidth of 5.5 GHz, sufficient to cover the fifth-generation (5G) millimeter-wave (mmWave) frequency bands n257, n258, and n261 (5.25 GHz), while reducing the height of the DRA by 38.5% compared to the conventional probe-fed RDRA (PF-RDRA). Additionally, the 4 dBi realized gain bandwidth of the proposed CFPL-ML-RDRA is 5.4 GHz, which is 28.6% broader than that of the conventional PF-RDRA. To experimentally verify the antenna’s performance, the CFPL-ML-RDRA mounted on a test printed circuit board with a small ground size of 3.2 × 3.2 mm² was fabricated and characterized. The measured data align well with the simulated data. Furthermore, excellent antenna array performance was achieved based on array simulations. Therefore, the proposed antenna structure is well-suited for 5G mmWave mobile applications. Full article

This work presents the development and characterization of a flexible capacitive electrode for non-contact ECG acquisition, fabricated using a simple and cost-effective method from readily available materials. The electrode consists of a multilayer structure with a copper conductor laminated by a polyimide (Kapton^®) dielectric layer on a polyurethane support. The impedance and capacitance of the electrode were evaluated under varying textile moisture levels with artificial sweat, as well as after exposure to common disinfectants including ethyl alcohol and iodine tincture. Electrochemical impedance spectroscopy (EIS) and broadband impedance measurements (10⁻¹–10⁵ Hz) confirmed stable capacitive behavior, moderate sensitivity to moisture, and chemical stability of the Kapton–copper interface under conditions simulating repeated use. A custom front-end readout circuit was implemented to demonstrate through-textile ECG signal acquisition. Simulator tests reproduced characteristic waveform patterns, and preliminary volunteer recordings confirmed the feasibility of through-textile acquisition. These results highlight the promise of the electrode as a low-cost platform for future wearable biosignal monitoring technical research. Full article

Broadband absorption of electromagnetic energy plays an important role in energy harvesting and stealth. Here, we present and demonstrate an absorber with a wide bandwidth of 2.1 μm in mid-infrared. The trapezoidal metamaterial consists of alternating silicon carbide and dielectric films. We have numerically demonstrated that an ultrahigh absorption energy efficiency higher than 97.7% can be calculated from 10.6 μm to 12.7 μm. The proposed absorber has high absorption efficiency at a wide-angle range. The simulation results are consistent with the theoretical calculation based on effective medium theory. The theoretical model simplifies the multilayer structure into an effectively homogeneous metamaterial with hyperbolic dispersion. In addition, the distributions of magnetic field depict that different wavelengths can be trapped at structures with various widths. The mechanism of this phenomenon is attributed to the slowlight modes. Furthermore, a dual-sized absorber is designed to achieve high efficiency and broadband absorption, which is easy to manufacture. Our study has potential applications in the areas of energy harvesting materials, thermal emitters and photovoltaic devices in the mid-infrared. Full article

Trap states in 2D transition metal dichalcogenides significantly affect the responsivity and response time of photodetectors, and previous ReS₂/Si-based heterojunction photodetectors have struggled to simultaneously achieve high responsivity and fast response. To address this issue, we developed a n-type ReS₂/p-type Si heterojunction photodetector through interface engineering. Specifically, the silicon substrate with a silicon dioxide dielectric layer was treated with inductively coupled soft plasma to adjust the thickness and surface states of the dielectric layer. This treatment created a multilayered heterostructure, which increased carrier concentration, effectively passivated sulfur-vacancy-induced defects, and thereby improved responsivity. Experimental results showed that the silicon-based n-type ReS₂ photodetector achieved a responsivity of 0.88 A W⁻¹ with a rapid response rise time of 2.5 s, a significant improvement from the intrinsic values of 12 mA W⁻¹ responsivity and 6 s rise time. Additionally, due to the defect-tunable nature of this pretreatment technique, the device exhibited enhanced Raman peaks and intensified photoluminescence (PL) absorption features, confirming the effectiveness of the interface engineering in optimizing device performance. Full article

This paper presents the design of a circularly polarized RFID ground mat antenna for UHF-band sports-event applications. Considering a practical sports-event timing system, the ground-based mat antenna with characteristics of a low-backward radiation and circular polarization is proposed. A multilayer square patch antenna using an acrylic dielectric substrate with a wideband branch-line coupler feeding network is employed to improve overall radiation efficiency, which, in turn, provides two excitation port with a phase difference of 90°. Thus, right-hand circular polarization can be obtained. Instead of a conventional FR4–air–FR4 structure, the proposed FR4–acrylic–FR4 composite configuration is adopted to substantially increase the antenna’s mechanical strength and durability against external pressure from runners. The antenna’s performance is attributed to the use of an effective composite dielectric constant and an optimized design of its parameters. Additionally, the patch antenna’s low-backward radiation characteristic helps reduce multipath interference in real-world applications. The measured results are in good agreement with the simulated data, validating the proposed antenna design. In order to further assess the practical performance of the antenna, outdoor measurements are carried out to validate the estimated reading distances derived from controlled anechoic chamber tests. The measured return loss remained below −10 dB across the frequency range of 755–990 MHz, exhibiting a slight discrepancy compared to the simulated bandwidth of 800–1030 MHz. For the characteristic of the circular polarization, the measured axial ratio is below 3 dB within the range of 860–920 MHz. While a more relaxed criterion of an axial ratio below 6 dB is considered, the operating frequency range extends from 560 MHz to 985 MHz, which falls within the frequency band relevant for RFID reader applications. Full article

The hyperbolic properties are demonstrated in Cantor photonic multilayers, which exhibit quasi-periodicity and consist of graphene and dielectric layers, forming a centrosymmetric structure. Different from the traditionally periodic hyperbolic metamaterials, here we introduce the concept of layer weight in quasi-periodic photonic multilayers; the equivalent permittivity tensor presents a hyperbolic dispersion with a specific weight of dielectric thickness. Subsequently, the dispersion relation transforming from hyperbolicity to ellipticity has been explored. The tunability of the hyperbolic properties can be enhanced by varying the Fermi energy of the graphene, the thickness of the dielectric, the relaxation time of graphene, and the number of graphene monolayers. The reflectance and transmittance of light waves in the quasi-periodic hyperbolic metamaterials depend on the hyperbolically dispersive speciality strongly as well. This research provides theoretical guidance for the design and optimization of photonic devices based on hyperbolic metamaterials. Full article