Optical and Quantum Electronics最新文献

Visible Light Communication (VLC) has emerged as a viable alternative to traditional radio frequency (RF) systems, offering inherent advantages such as high bandwidth availability, electromagnetic interference immunity, and enhanced physical-layer security. Despite these benefits, VLC systems employing multi-carrier modulation continue to face major challenges, particularly high Peak-to-Average Power Ratio (PAPR) and elevated Bit Error Rates (BER), which hinder overall system efficiency and reliability. This paper introduces a novel hybrid VLC architecture that synergistically combines Adaptive Symbol Reshaping (ASR) and Generalized Optical Spatial Modulation (GOSM) within both Orthogonal Frequency Division Multiplexing (OFDM) and Filter Bank Multicarrier (FBMC) transmission frameworks. The proposed ASR technique dynamically adjusts symbol amplitudes to suppress peak power fluctuations, while GOSM leverages spatial domain modulation to enhance data throughput and robustness without increasing spectral load. Comprehensive simulation results validate the effectiveness of the proposed architecture. Notably, the integrated FBMC-ASR-GOSM system achieves up to 5.5 dB reduction in PAPR and delivers BER improvements exceeding 81% compared to conventional OFDM systems. These enhancements underscore the system’s potential for enabling high-performance, energy-efficient, and scalable VLC solutions tailored for next-generation indoor wireless networks.

Herein, thermally evaporated CdSe thin films are interfaced with Bi₂O₃ nanosheets to construct a conduction band aligned heterojunction device suitable for nonlinear optical applications. Depositing of Bi₂O₃ nanosheets onto CdSe, increased the crystallite size and decreased the strain and line defects concentration by 15.4%, 12.2% and 23.1%, respectively. Bi₂O₃ nanosheets successfully narrowed the energy band gap of CdSe. The absorption improved by 403%, and optical conductivity, dielectric constant and terahertz cutoff frequency are increased by 498% 60% and 302% near 1.65 eV, respectively. In addition, formation of zero conduction band offset and large valence band offset of 1.55 eV, resulted in high drift mobility and free carrier density values of 27.75 cm²/Vs and 4.0(:times:{10}^{17}{text{cm}}^{-3}) making the device attractive for terahertz transistors technology. Moreover, the calculated first and third order nonlinear susceptibility exhibited values of 0.3–0.5 esu, 10⁻¹¹-10⁻¹² esu, respectively. Bi₂O₃ coating onto CdSe resulted in the enhancement in the nonlinear refractive index by more than 100%. The enhancement reached 1000% at 1.80 eV. The response of the CdSe/Bi₂O₃ to the intensity of light passing through it improved by 300%. Furthermore, the ratio of the volume energy loss factor to the surface energy loss factor is always larger than one indicating the domination of the bulk plasmonic excitations which are essential in plasmonic applications.

This study employed computational and experimental methods to investigate the structural and electronic modifications of pure and Zn-doped cubic NiO. Density Functional Theory (DFT) simulations were conducted using the Quantum Espresso package with the Perdew–Burke–Ernzerhof (PBE) functional, incorporating a Hubbard U correction (DFT + U), U = 6 eV) to describe the localised 3d orbitals of Ni accurately. A 2 × 2 × 2 supercell of NiO was constructed, and Zn dopants were introduced by substituting Ni atoms at 2%, 4%, and 6% concentrations. Convergence tests confirmed the suitability of the parameters: cutoff energy (50 Ry), k-point mesh (7 × 7 × 7), and equilibrium lattice constant (4.22 Å). The band structures, density of states, and total energies were analysed using XCrySDen and VESTA visualisation tools. Experimentally, NiO nanoparticles were synthesised via precipitation followed by calcination at 350 °C. The agreement between theoretical and experimental findings is clear. This reinforces the conclusion that the structural framework of NiO remains stable. X-ray photoelectron spectroscopy confirmed Ni²⁺ and O²⁻ states with surface hydroxyl groups aiding photocatalysis. DFT revealed bandgap narrowing from 2.89 to 2.74 eV with Zn doping, linked to Fermi level shifts. Zn doping enhances NiO’s crystallinity, electronic structure, and optical properties, making it promising for photocatalytic and photovoltaic applications.

Future optical access networks will have significant challenges in achieving energy efficiency, flexibility, and reliable communications links. Data-intensive applications such as Augmented/Virtual Reality (AR/VR), holographic communications, autonomous driving, high-precision manufacturing, and ultra-massive machine-type communications will require high throughput, resilient transmission links, high speed, and high energy efficiency. This paper proposes a fault-protected Single Mode Fiber (SMF) / Free Space Optics (FSO) ring-based pay-as-you-grow hybrid Wavelength Division Multiplexed (WDM) and Time Division Multiplexed (TDM) optical network to create a highly reliable architecture for delivering seamless connectivity to the end users. The proposed architecture can provide uninterrupted high-speed WDM Point-to-Point (P2P) downstream and upstream transmission. The proposed ring topology-based architecture can migrate traffic to an alternative route whenever any fault occurs in the main distribution ring. The dynamic resource allocation using the pay-as-you-grow model helps reduce energy requirements. It can give a Q-factor more than 6 for both fault-free situations (normal condition) and scenarios for multiple faults at different locations. In addition, the proposed architecture can reduce energy requirements by up to 80% using a pay-as-you-grow model. The availability of an alternative link during faults in the SMF link is around 76.65% for the considered representative traffic pattern. The architecture can be deployed to handle traffic from Internet of Things (IoT) and smart city applications that require high-speed and reliable internet connectivity.

The dynamics of bright and W-shaped dispersive solitons in birefringent optical fibers described by the coupled Radhakrishnan–Kundu–Lakshmanan equation (cRKL) without four-wave mixing (FWM) is studied. One of the main novelties of the study consists in finding exact analytical solutions with the aid of the Jacobi elliptic cn function method and an explicit detailed study of their behavior in the presence of the physical effects characteristic of ultrafast fiber optics, i.e. self- phase modulation (SPM), third order dispersion (TOD), cross-phase modulation (XPM), and self-steepening (SS). The cRKL equation is a universal nonlinear wave equation for orthogonal polarization modes in birefringent fiber. Graphical analysis shows that the soliton profile changes significantly with various parameter values. Negative TOD results in soliton-broadening and amplitude increase, and positive TOD leads to pulse compression, and provides a mechanism for dispersion-managed optical systems. Self-steepening induces temporal asymmetry and pulse narrowing, useful in the application of femtosecond pulse shaping. XPM controls intermodal energy transfer and affects generating soliton and cross-talk suppression in polarization-division multiplexed systems. SPM leads to pulse shortening and spectral confinement, this being critical for short-pulse compression and supercontinuum generation. Based on exact analytical solutions incorporating nonlinear and dispersion effects, this analytic-and-graphic description gives a coherent picture for engineering soliton propagation in nonlinear birefringent media. Our investigations resulted in W-shaped and bright solitons without FWM with the action of SPM, TOD, XPM, and SS, being calculated. The advancement implies that there are more potential ways of controlling the soliton dynamics by means of ultrafast photonic components, such as femtosecond pulse shaping, dispersion managed amplification, and polarization division multiplexing.

Magnetic nanoparticles fabrication for various applications requires finding a way to control their morphology and size in a wide range. The technique of pulsed laser ablation in liquid looks promising to reach this aim. For further improvement in this direction, we propose using thin magnetic films as ablation targets. This paper demonstrates the possibility of synthesizing magnetic nanoparticles by pulsed laser ablation of cobalt nanofilms with 5–500 nm thickness in water. The presence of unoxidized Co within the nanoparticles imparts them magnetic properties at room temperature. The morphology, mean size and size dispersion of the nanoparticles depend on the thickness of the ablated targets. When the nanofilms thickness exceeds 35 nm (the skin layer depth), laser ablation results in the formation of the almost spherical particles with less than 100 nm mean size and 40% relative standard deviation in size. In the case of laser ablation of nanofilms less than 35 nm thick, one can observe both spherical and flocculent structures up to 1 μm in size, but with a smaller size dispersion. This difference can be explained by the features of light absorption and laser-induced heating over the film depth: incident light is absorbed predominantly within the skin layer regardless of the film thickness, while thermal diffusion allows the heat to propagate deeper in thicker films. These features are also manifested in dependencies of the laser ablation crater diameter and the ablation threshold on the film thickness.

NiO epitaxial nanofilms have been successfully deposited on LiNbO₃ substrates by magnetron reactive sputtering and optimal deposition conditions to achieve high crystalline perfection of these films have been found. The structural, optical and electrical properties of NiO/ LiNbO₃ films have been studied by X-ray diffraction, atomic force microscopy (AFM), UV–visible spectroscopy, and I–V measurements. The XRD shows that NiO films grown on LiNbO₃ substrates are highly crystalline with a rocking curve FWHM = 0.04⁰. The optical transparency of NiO films and LiNbO₃ substrates in the wavelength range of 250–800 nm has been studied. The band gaps of nickel oxide films grown on LiNbO₃ substrates are in the range of 3.57–3.59 eV. Metal-semiconductor-metal (MSM) diode structures in the form of interdigital Schottky barrier contacts to the epitaxial NiO have been manufactured. The current-voltage characteristics of the MSM-diodes demonstrate low dark currents and show the potential of diode structures for the elaboration of narrow-band detectors of UV-radiation.

Generation of near-IR to mid-IR light spectrum is essential for advancing techniques like environment monitoring, mid-IR spectroscopy, sensing, guided missile technology, quantum communication, etc. Nonlinear optical phenomena are key for developing mid-IR light sources. In this paper, numerical analysis of dispersion-tailored tellurium oxide (TeO₂) on-chip waveguide devices on sapphire substrate have been presented to tune zero dispersion wavelengths (ZDWs) at 1.55 μm and 2 μm. Two different waveguide designs are reported: a TeO₂ rib waveguide design that attains ZDW at 1.55 μm, and a TeO₂-coated SiN hybrid waveguide design that achieves ZDW at 2.05 μm for maximum power transfer through the waveguide devices. The numerical simulations illustrate the suitability of the waveguide device on a sapphire substrate for generating mid-IR spectrum using conventional laser sources operating at 1.55 μm and 2 μm. Additionally, at 1.55 μm TeO₂ rib waveguide design exhibited 0.15 × 10⁻² dB/cm confinement loss and 1430 (W.Km)⁻¹ nonlinearity values. While TeO₂-coated SiN hybrid waveguide design shows confinement loss of 0.15 × 10⁻³ dB/cm, and nonlinearity of 829 (W.Km)⁻¹ at 2 μm wavelength. Designs of both waveguides show dispersion characteristics in anomalous regions and can be significantly used to generate nonlinear applications using commercially available sources and extend their functionality in integrated photonics.

In this study, the extended Huygens-Fresnel integral formula in the paraxial approximation and the Rytov theory are used to evaluate and numerically investigate the average intensity of the Pearcey-Gaussian (PG) beam propagating in a turbulent environment. On the other hand, the numerical results show that the average intensity of the PG beam in a turbulent environment depends on the turbulence strengths, the beam waist, the distance of the propagation and the wavelength. Furthermore, potential applications in information transmission, optical sorting, optical trapping, and other fields are anticipated to benefit from our findings.