Optical and Quantum Electronics最新文献

We present a comprehensive computational analysis of visible light interference patterns from three input beams. High-contrast interference fields, like hexagonal intensity lobe lattices, are produced by carefully examining a variety of input beam characteristics, angular orientations, and polarization. The simulations are based on scalar wave theory under the paraxial approximation and are performed on a subwavelength-resolution spatial grid to resolve fine-scale intensity characteristics. Optimized patterns induce photorefractive effects in LiNbO₃, permanently imprinting crystals via exposure. Defect sensitivity is evaluated in another investigation by introducing nanoscale anomalies (~ 10 nm), which result in observable disruptions in high-intensity regions of the interference pattern. Our approach makes it easier to design defect-sensitive photonic structures and offers a practical path to real-time monitoring and precise manufacturing of nonlinear optical devices. 

Adhesion layers play a crucial yet often overlooked role in determining the optical performance of plasmonic nanostructures. In this work, a three-dimensional finite-element modeling framework is employed to systematically quantify how adhesion-layer material and thickness influence nanofocusing efficiency in tapered metal–insulator–metal (MIM) waveguides. Titanium (Ti), chromium (Cr), germanium (Ge), and self-assembled monolayers (SAMs) are compared over a thickness range of 1–10 nm under identical geometrical and excitation conditions, enabling direct isolation of adhesion-layer-induced optical losses. The simulations show that even ultrathin metallic adhesion layers (1–3 nm) introduce severe absorption losses, reducing coupling efficiency by more than 50% and approaching 90% at 10 nm. In contrast, SAMs preserve high throughput and strong field confinement due to negligible absorption and improved impedance matching, while Ge exhibits intermediate behavior and serves as a comparative optical case. These results establish a predictive, fabrication-relevant framework for understanding interfacial optical losses in plasmonic MIM nanofocusing structures and provide quantitative design guidelines for selecting low-loss adhesion strategies in nanophotonic, sensing, and data-storage applications.

Antimony chalcogenides (Sb₂Se₃ and Sb₂S₃) are increasingly recognized as promising absorber materials for thin-film solar cells owing to their strong optical response, natural abundance, and environmental compatibility. However, the device performance is still limited by an insufficient rear contact barrier, a high density of point defects in the bulk, a reduced carrier lifetime, and defect states at the interfaces. In this work, the Vienna Ab initio Simulation Package (VASP) is employed to investigate their structural and optoelectronic properties. Sb₂Se₃ and Sb₂S₃ exhibit direct band gaps of 1.17 eV and 1.62 eV, respectively, along with strong UV–visible absorption (~ 10⁵ cm⁻¹), confirming their suitability for efficient solar energy conversion. To leverage these properties, an optimized device architecture is proposed using SCAPS-1D, enabling simultaneous utilization of above- and sub-bandgap photons. The structure embeds a low-bandgap absorber within a high-bandgap matrix, forming a straddling-type heterostructure with favourable band alignment. This configuration is integrated with p⁺ and n⁺ layers to establish a strong internal electric field, which enhances carrier transport and suppresses recombination. Furthermore, different aspects of carrier transport within the confinement region are examined, along with key physical parameters—such as thickness, position, and barrier height—that govern overall device performance. The optimized configuration yields a theoretical power-conversion efficiency of ~ 35% under ideal conditions, exceeding conventional single-junction limits but serving as a simulation-based upper-bound prediction rather than an experimentally achieved value. The results provide a predictive roadmap for guiding future experimental optimization of stable, high-efficiency Sb-chalcogenide solar cells.

The ever-growing demand for high-speed data has challenged the conventional wireless transmission systems. In this paper, we propose a single-channel high-speed bandwidth-efficient free space optics (FSO) transmission by incorporating hybrid Polarization Division Multiplexing (PDM)-Orbital Angular Momentum (OAM) Multiplexing-Orthogonal Frequency Division Multiplexing (OFDM) using 16-level Quadrature Amplitude Modulation (QAM) signals. 2-OAM beams ((:{LG}_{text{0,0}}) and (:{LG}_{text{0,15}}):)of 2-orthogonal polarized beams are used to carry 640 Gbps of data over a free space channel by incorporating in-phase-quadrature modulation. At the receiver terminal, signal processing is implemented to rectify the signal distortion due to the free space channel losses. We analyzed the proposed system performance for varying weather conditions using standard performance metrics including constellation, Error Vector Magnitude (EVM), and Bit Error Rate (BER) over an increasing transmission range. The obtained results demonstrate reliable 640 Gbps transmission using the proposed system with a range varying from 703 m to 7 km within forward error correction (FEC) limits of BER ≤ 3.8(:times:{10}^{-3}), EVM ≤ 17.5%, and clear constellation.

Since its artificial synthesis, the adaptability of graphitic carbon nitride (g-C₃N₄) in solar energy conversion and environmental remediation has made it a promising photocatalyst. However, its practical applications are hindered by intrinsic limitations such as low surface area, rapid electron-hole recombination, and limited quantum efficiency. Rare-earth elements provide a useful technique to improve light harvesting and charge transfer under low-energy stimulation because of their distinct 4f electronic structure and upconversion luminescence. In this work, we successfully synthesize Er₂O₃/g-C₃N₄ heterojunctions rich in oxygen vacancies using a simple hydrothermal process. The introduction of oxygen vacancies modulates the charge-transfer pathway, accelerates carrier mobility, and improves electron–hole separation, thereby boosting CH₄ generation rates by 50.21-fold and 74.89-fold compared to pristine Er₂O₃ and g-C₃N₄, respectively. The exceptional photocatalytic performance originates from three synergistic effects: Er³⁺induced upconversion luminescence converts low-energy near-infrared photons into visible emissions, enhancing solar light utilization; oxygen vacancies broaden light absorption and expedite carrier migration; and these vacancies act as active sites that facilitate CO₂ adsorption and activation. This study not only demonstrates a high-efficiency photocatalyst for solar-driven CO₂ reduction but also provides an innovative design paradigm for engineering g-C₃N₄-based heterostructures with optimized charge dynamics and light management.

We introduce a mesoscopic quantum well whose confinement and chirality emerge solely from the intrinsic twist of a finite helicoidal metric. This purely geometric construction requires no external gates or fields: the metric itself induces both a harmonic radial potential and a twist-driven Zeeman-like term that breaks the (m leftrightarrow -m) degeneracy. By imposing hard-wall boundary conditions at (z = pm L/2), we quantize the axial motion and obtain a genuinely zero-dimensional helicoidal quantum dot. An exact analytic solution reveals an energy spectrum with chiral splitting linear in both the twist rate (Omega ) and the axial quantum number (n_z). For realistic InAs nanoroll parameters ((L = 100) nm, (Omega = 5times 10^{6},mathrm {m^{-1}})), this geometric effect results in a measurable splitting of (2hbar omega simeq 1.040) meV. We propose three viable experimental platforms, ultracold atoms in optical traps, femtosecond-written photonic waveguides, and strain-engineered semiconductor nanorolls, where this twist-induced phenomenon should be accessible with current technology.

We theoretically investigate enhanced mid-infrared absorption in a one-dimensional zero-contrast grating structure incorporating a thermally tunable vanadium dioxide ((hbox {VO}_{2})) layer atop a metallic substrate. At lower temperatures, (hbox {VO}_{2}) remains in its insulating phase with low optical loss, enabling it to function as a low-loss cavity spacer that supports Fabry-Pérot resonances under transverse magnetic polarization. When combined with the guided mode resonance effects induced by the zero-contrast grating, strong optical field confinement occurs within the (hbox {VO}_{2}) layer, leading to pronounced absorption peaks at mid-infrared wavelengths (16–19 (mu )m). We employ rigorous coupled-wave analysis to systematically analyze the optical responses, revealing that proper tuning of the grating period (9–12 (mu )m), fill factor (0.2(-)0.8), and (hbox {VO}_{2}) thickness (3(-)3.5 (mu )m) results in narrowband absorptance exceeding 90% at resonance. The underlying molybdenum layer acts as a back reflector to suppress transmission, further enhancing light trapping. The absorption characteristics can be significantly modulated by the thermally induced phase transition of (hbox {VO}_{2}), offering dynamic control over resonant absorption. Additionally, the structure exhibits azimuthal angle-dependent behavior and supports enhanced absorption even under transverse electric polarization. The interplay between guided mode resonance and Fabry-Pérot cavity effects in the low-loss (hbox {VO}_{2}) phase offers a passive route to achieve spectrally selective and thermally switchable absorption. These findings have potential applications in tunable infrared sensors, thermal emitters, and actively controllable photonic devices.

The present study investigates how organic pigments adhere to the TiO₂ surface, which acts as a mesoporous film in dye-sensitized solar cells (DSSCs). The effect of this adhesion on the electronic band gap is of interest. In this regard, eight different density functionals were evaluated to identify the most appropriate computational method to accurately describe the electronic and optical properties of TiO₂ nanoparticles. The results obtained for the absorption maximum (λ_max) and band gap energy (E_g) were compared with valid experimental data and it was found that the LSDA functional provides results closely matching benchmark values. Then, geometric optimization and time-dependent density functional theory (TD-DFT) calculations were performed on the adsorption of Naphthoquinone on TiO₂. These calculations identified two stable structures with interaction energies of − 0.49 and − 0.21 eV (TN1 and TN2, respectively), in the gas phase. The study of the absorption of natural dyes Acacetin and Juglone on these surfaces also showed that Juglone acted as a stronger chemisorption agent, with its interaction energy (E_int) being as low as − 0.27 eV and − 0.19 eV a significant charge transfer (~ 291, and 267 |me|) occurred, resulting in a significant reduction of the band gap by 23.29% and 44.57% in the TN1J1 and TN2J1 complexes, respectively. Density of states analysis confirmed the presence of new frontier orbitals, contributing to the improved of electronic conductivity. The optical absorption spectra also showed a shift towards longer wavelengths and an increase in absorption intensity for the dye-TiO₂ complexes, especially the Juglone-containing structures (TN2J1) with an absorption intensity of 0.1023, which improved the visible light harvesting ability. Overall, the results demonstrate the remarkable effect of functionalizing TiO₂ with Naphthoquinone-based natural dyes and introduce Juglone as a promising sensitizer. It improves efficiency and stability of dye-sensitized solar cells by enhancing the photophysical and electronic mechanisms.

This work presents an analytical model to optimize the efficiency of a mechanically stacked four-terminal (4-T) tandem solar cell composed of a (FAPbI₃)_1−x(MAPbBr₃)_x perovskite top cell and a Graphene/GaAs bottom cell. The perovskite absorber’s tunable bandgap, ranging from 1.52 to 2.31 eV, enables effective spectral matching with the fixed 1.42 eV bandgap of the GaAs subcell. The model incorporates experimentally validated optical and electrical parameters for subcells under AM1.5G illumination, allowing accurate modeling of the tandem device’s J–V characteristics. By systematically optimizing the absorber thickness and bandgap composition, the study demonstrates that a planar tandem configuration with top and bottom absorber thicknesses of 1 μm and 2 μm respectively can achieve a power conversion efficiency (PCE) of 28.3%. Implementing a textured surface on the top cell significantly enhances light trapping and reduces reflection losses, further increasing the PCE to 31.9%. This surface texturing improves photon absorption in the perovskite layer while maintaining sufficient light transmission to the bottom cell. The results identify an optimal top-cell bandgap of approximately 2.31 eV, balancing photon harvesting and transmission for maximal tandem efficiency. This work uniquely combines bandgap tuning, thickness optimization, and surface texturing in a 4-T perovskite/Graphene/GaAs tandem structure, offering practical insights for next-generation solar cell design.

While highly efficient solar cells use halide perovskites containing Pb, the unstable nature of the methylammonium (MA) cation at high temperatures interacting with lead iodide (PbI₂) lattice is challenging and may hinder the commercialization of these devices. Here, a method is proposed to completely prevent the organic cation rotation in MAPbI₃ perovskite by the substitution of CH₃COHNH₂⁺ (Ac) cation in the resonance form based on the calculations on structural, electronic and optical properties using Wien2k code with the FP-LAPW method. To observe the effect of Ac cation on power conversion efficiency (PCE), the structures of AcPbI₃ and MAPbI₃ perovskite solar cells (PSCs) with thin thicknesses (100–300 nm) are investigated using a solar cell capacitance simulator, numerically reproducing photocurrent–voltage characteristics and exciton generation rates of the perovskite structures. The electronic bandgap, optical conductivity, open-circuit voltage, photocurrent, fill factor, and PCE of AcPbI₃ PSC are found to be about 1.63 eV, 1340 Ω⁻¹ cm⁻¹ (in the visible region), 1.062 V, 24.90 mA cm⁻², 0.88, and 23.16%, respectively. Based on the electrical simulation results and a comparison of the proposed cation with the MA cation, a 29.74% efficiency improvement is achieved. Accordingly, the results envision a new path for the commercialization of PSCs with high efficiency and stability.