Optical and Quantum Electronics最新文献

This paper introduces a novel reflective metasurface for efficient polarization conversion in the X, Ku, and K bands. Through rigorous simulations and experimental validation, high polarization conversion ratios (PCR) exceeding 90% were achieved, even at incidence angles up to (45^circ). Superior performance in the axial ratio (AR) and ellipticity values was demonstrated, showcasing the versatility of the designed metasurface in linear-to-linear and linear-to-circular polarization conversions. Comparative analysis against existing metasurfaces revealed the superiority of the proposed design in polarization conversion, particularly in Linear polarization, left-hand circular polarization, and right-hand circular polarization scenarios. The experimental results closely align with simulation outcomes, with minor discrepancies attributed to fabrication imperfections and antenna misalignments. This study advances metasurface-based polarization converters, offering promising applications in wireless communication, radar systems, quantum optics, and sensing technologies.

The structural, electronic, elastic, and optical properties of Half Heusler YSbPd and YSbPt were investigated with PBE and RPBE functions using GGA implemented with Density Functional Theory (DFT). Structural stability was verified using the Birch–Murnaghan equation of states for optimization. The obtained lattice parameters match previous literature data. The Elastic stability is computed the Elastic constants by using the Code version: 2024.03.15 (running on Python 3.11.2). Our results show that both compounds are ductile in nature. The Calculated the Band structures of half-Heusler YSbPd and YSbPt show direct band gaps of approximately 0.154 and 0.412 eV, respectively, which indicate a semiconducting nature. The Sb and Pd/Pt states are mainly responsible for the conduction state, as evidenced by the density of states (DOS) plot. Optical properties such as dielectric function, reflectivity, refractive index, conductivity, and loss function were investigated in the energy range of 0–10 eV. The maximum absorption and low loss indicate that YSbPd and YSbPt are potential candidates for optoelectronic device applications.

Skin cancer involves abnormal growth of skin cells, typically caused by ultraviolet radiation exposure. Timely and accurate detection is essential to mitigate significant health risks and ensure effective treatment. This paper proposes a nanoantenna to enhance diagnostic and therapeutic capabilities for skin cancer detection. These antennas, emitting electromagnetic waves in the terahertz band (0.1–10 THz), improve integration for miniaturized wireless systems and serve as a foundation for the Internet of Medical Things (IoMT). We design a miniaturized, metamaterial-inspired gold-patch axe-shaped nanoantenna ((121.97 times 110 times 17) (mu m^3)), implemented in CST Studio Software. The antenna resonates at 1.152 THz, with a very low return loss ((<-55) dB), a gain of 2.42 dBi, and a bandwidth of 40 GHz. The proposed antenna can be used as a sensor, considering the S11 spectra as a key parameter to differentiate between normal and cancerous skin (i.e., basal cell carcinoma). The simulation demonstrates significant and quantifiable differences between normal and cancerous skin and also highlights the proposed antenna’s suitability for applications such as radar systems, satellite communications, and advanced measurement technologies.

Single crystals of pyridin-4-aminium butanedioate (PAB) were synthesized and its physiochemical properties were studied to explore its optical limiting behavior in laser photonics. The centrosymmetric behaviour and the monoclinic crystal system is confirmed by Single Crystal X-ray diffraction method and its lattice parameters are calculated and compared with the CCDC database. The structure is optimized to understand the structural stability and the intermolecular interactions are confirmed with the help of Hirshfeld surface analysis. The major donor and acceptor interactions required for structural stabilization is analysed with the aid of Natural Bond Orbital analysis. The melting point and the thermal decomposition are scrutinized by TG/DTA analysis. The laser reliability was examined by Laser Damaged Threshold studies. The electronic transitions and the optical parameters are evaluated which indicates that the material has low band gap and high transmittance near the visible region. The electron transport and charge transfer interactions were examined by HOMO–LUMO and Molecular Electrostatic Potential analysis. The PAB possess excellent nonlinear absorption coefficient at room temperature and the low optical limiting threshold recommends to develop nonlinear absorption induced optical limiting applications.

Polymer nanocomposites have been developed using polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) as base polymers, with iron (III) oxide (Fe₂O₃) and molybdenum trioxide (MoO₃) serving as nanofiller materials. The results of XRD and FTIR studies verified the effective integration of FeO₂/MoO₂ nanoparticles into the polymer matrix and their interactions with polymer chains, which resulted in changes to the crystalline structure and chemical bonding of the nanocomposite. The SEM analysis reveals that adding mineral oxides (Fe₂O₃/MoO₃) to the PVA/CMC blend transitions the morphology from smooth and homogeneous to increasingly disordered due to filler-induced aggregation. As the Fe₂O₃/MoO₃ concentration increased, the indirect optical bandgap reduced from 4.43 to 2.88 eV, improving the photoresponsiveness of the material. Moreover, the refractive index rose from 1.63 to 2.72, indicating the material’s suitability for optical applications. The magnetic properties of the PVA/CMC-Fe₂O₃/MoO₃ nanocomposite were evaluated at room temperature using the VSM technique, showing ferromagnetic behavior with a notable rise in saturation magnetization (Ms), remanent magnetization (Mr), and loop area (La) as the Fe₂O₃/MoO₃ content increased. The prepared films demonstrated higher AC conductivity values than the pure PVA/CMC. The dielectric permittivity and modulus display tunable properties, offering promising potential with different concentrations of PVA/CMC-Fe₂O₃/MoO₃ nanoparticles in the PVA/CMC matrix. These results underscore the promise of PVA/CMC-Fe₂O₃/MoO₃ nanocomposites for optoelectronic applications, where key factors for example enhanced light absorption, an increased refractive index, and improved charge transport play a crucial role in device performance.

Graphical Abstract

The preparation steps of PVA/CMC-Fe₂O₃/MoO₃ nanocomposite films.

The all-fiber inline polarizer (AFILP) is gaining prominence in fiber optic sensing and laser technologies due to its compact design and strong resistance to interference. However, its further development is hindered by the issue of optical loss. To address this challenge, we propose a low-loss AFILP that incorporates a composite structure of graphene oxide and nanogold film, applied to D-shaped fibers polished to varying depths. Experimental results demonstrate that the polarization extinction ratio (PER) and the insertion loss (IL) of the transmitted polarization in a nanogold-coated D-shaped fiber are positively correlated with the distance from the fiber core at specific polishing depths. For instance, at a distance of 4 µm from the fiber core center, the PER reached 38.82 dB, while the IL was 2.831 dB. Notably, at the same polishing depth, the all-fiber polarizer incorporating a composite structure of graphene oxide and nanogold film exhibited a PER of 36.65 dB, along with an exceptionally low IL of 0.2 dB, corresponding to the loss of the transmitted polarization.These findings suggest that the composite structure effectively reduces insertion loss while maintaining high PER, offering significant potential for enhancing AFILP performance. Additionally, the graphene oxide layer was formed by drying a graphene oxide dispersion, providing a cost-effective and straightforward alternative to traditional graphene coating methods.

This study employs first-principles density functional theory (DFT) to comprehensively investigate the structural, electronic, magnetic, optical, and thermoelectric properties of the FeMnCrGe quaternary Heusler alloy, an unexplored material. Using the WIEN2k simulation package, the crystal structure was optimized with the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method and the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA). The optimized lattice constant of 5.8076 Å and a negative formation energy confirm the alloy’s thermodynamic stability. Elastic analysis reveals a brittle nature, with a high Young’s modulus and a Poisson ratio of 0.229, indicating the predominance of covalent bonding. The computed electronic structure verifies the alloy's half-metallic nature, with the spin-up state acting as a metal and the spin-down state as a semiconductor. This behavior is accompanied by an indirect band gap (Γ-X) of 0.974 eV, determined via the mBJ approximation. The total magnetic moment of 1.00 μB demonstrates the compound's compliance with the Slater-Pauling rule, affirming its stable ferromagnetic nature. Characterized by a high refractive index across the visible wavelengths, as well as strong ultraviolet absorption, this material is highly suitable for photovoltaic use. The alloy’s thermoelectric performance, assessed with the BoltzTraP code, is marked by a Seebeck coefficient of 124.1 μV K⁻¹ and a figure of merit of 0.42 at 500 K, suggesting its effectiveness for energy conversion. These insights highlight FeMnCrGe's potential as a multifunctional material for spintronics and photovoltaics and suggest experimental validation for practical implementation.

This study introduces an advanced broadband absorber design featuring titanium-based square ring resonators on silicon dioxide substrates, optimized for superior absorption performance across visible and infrared wavelengths. The proposed absorber leverages a metal–insulator–metal configuration with a titanium resonator layer, SiO₂ substrate, and tungsten ground layer, achieving over 94% absorption across the 0.7–4 μm wavelength range, with peak efficiency surpassing 99% at 2.142 μm. Unlike conventional designs relying on noble metals, the proposed absorber utilizes titanium, offering a cost-effective, thermally stable, and scalable solution suitable for high-temperature applications. The key novelty of this work lies in integrating machine learning, specifically K-Nearest Neighbour (KNN) regression, to predict and optimize the absorption characteristics, achieving R² values of up to 0.99. This approach facilitates rapid design iterations, ensuring robust performance under varying structural and environmental conditions. Furthermore, the absorber demonstrates exceptional angular and polarization independence, maintaining high efficiency under both transverse electric (TE) and transverse magnetic (TM) polarizations. These attributes make the proposed design an innovative and versatile solution for applications in solar energy harvesting, thermal management, and broadband photonic sensing.

The present study reports the structural, electronic, magnetic, and optical properties of vanadium-doped Li₂Te using the ab-initio simulations within the framework of density functional theory. To account for exchange-correlation effects, the PBE-GGA, PBE-GGA-mBJ, and PBE-GGA+U approximations were employed. Our findings reveal that the ground state of vanadium-doped Li₂Te is ferromagnetic, with the ferromagnetic behavior predominantly arising from strong spin-splitting effects on the d orbitals of vanadium atoms. The formation energy (({E}_{F})​) was calculated to confirm the thermodynamic stability and alloying feasibility of the compound at zero temperature. The negative value of ({E}_{F})​ indicates favorable alloying stability. Electronic structure analysis demonstrates that the material exhibits half-metallic ferromagnetic behavior, characterized by 100% spin polarization at the Fermi level. This property makes it a promising candidate for spintronic applications. To further understand the magnetic interactions, the s(p)-d exchange coupling constants (({N}_{0alpha }) and ({N}_{0beta })) were computed, revealing significant exchange splitting effects in both conduction and valence bands. These findings provide comprehensive insights into the multifunctional properties of vanadium-doped Li₂Te, offering valuable references for its potential applications in next-generation spintronic devices.

In this paper, a dual-controlled tunable polarization-independent triple-band absorber using hybrid bulk Dirac semimetal (BDS) and vanadium dioxide (VO₂) metamaterial is proposed. The physical properties of the absorber can be theoretically analyzed by the equivalent circuit model (ECM). When the Fermi energy of BDS increases from 0.11 to 0.15 eV, the peak frequencies also gradually increase and blue shift occurs. In addition, When the VO₂ is in fully metallic state, the absorber exhibits three distinct absorption peaks with absorptances of 99.76%, 99.61% and 99.76%, respectively, with an average absorptance of 99.71%. As the the transition of VO₂ from fully metallic state to insulating state, the transmittance and reflectance increase and the absorptance gradually decreases. Moreover, due to the structure symmetry of the absorber, the absorptance exhibits polarization independent behavior. Finally, the modulations of absorptivity spectra by tailoring the structure dimension and the potential for the application of the absorber as a refractive index sensor, are further discussed. This study provides potential applications in the design of multi-band dual–controlled tunable sensors, filters and absorbers.