Optical and Quantum Electronics最新文献

In this work, the pure SnO₂ and Cu-doped SnO₂ nanoparticles (NPs) were prepared with various Cu doping level (0, 5, 10 and 15 wt%) by employing the co-precipitate method. The study focused to investigating the role of Cu doping on structural, morphological, optical, and electrical properties of SnO₂ NPs. The structural pattern confirmed the formation of pure SnO₂ NPs, and also the doping of Cu into it. The SEM morphologies appeared as agglomerated larger granules arranged in a random orientation. The TEM images indicate that the nanoparticles are nearly spherical and tend to aggregate into clusters. The XPS spectra confirm the presence of Sn, Cu, O elements, and also the Cu²⁺ doping into the SnO₂ system. The optical bandgap showed an increased absorption value and also a decrease in bandgap with respect to the Cu doping. The FTIR spectra revealed the presence of the Sn–O stretching vibration as well as the O–Sn–O bending vibration and the successful alteration of functional groups by Cu doping. The prepared NPs were used as an n-type layer for the n-SnO₂/p-Si and n-Cu@SnO₂/p-Si junction diode fabrication. The calculated ideality factor of the diodes decreased continuously with the Cu doping level. Also, the maximum photosensitivity of 960.61% was achieved for 15 of n-Cu@SnO₂/p-Si diode due to higher photocurrent. The barrier height values were found to be varied from 0.715 to 0.864 eV. The detectivity (D*) was observed in the range of 10⁹ Jones. Hence, the fabricated n-Cu@SnO₂/p-Si diodes will be more suitable for upcoming optoelectronics applications.

The melt-quench process was employed to fabricate (50-x)Li₂O-xMnO₂-50B₂O₃ glasses with varying MnO₂ content (0 to 20 mol %). X-ray diffraction (XRD) confirms the amorphous nature of all glass samples. Electron Diffraction Spectra (EDS) confirms the presence of elements in the glass network. Structural analyses using Fourier-transform infrared (FTIR) and Raman spectroscopy revealed a gradual conversion of tetrahedral BO₄ units into trigonal BO₃ units with increasing MnO₂ content, indicating that MnO₂ acts as a network modifier. This modification enhances the concentration of non-bridging oxygen (NBO) sites, consistent with the observed decrease in glass transition temperature. Optical studies using UV–Vis diffuse reflectance spectroscopy (DRS) showed characteristic Mn²⁺ absorption bands and a reduction in optical band gap from 3.77 to 1.00 eV. A significant enhancement in third-order nonlinear susceptibility (χ³), from 0.009 to 0.473 × 10⁻¹⁰ esu was observed with increasing MnO₂ content, along with increase in optical basicity (Λ(E_g)) from 0.99 to 1.145. These results demonstrate that Mn incorporation induces substantial structural and electronic modifications, making the developed glass system a promising candidate for nonlinear photonic and optoelectronic device applications.

In this paper, we investigate theoretically the fourth-order dispersion (FOD) influence on the modulation instability (MI) gain spectra in the presence of higher-order effects in the triple-core oppositely directed coupler with positive–negative-positive index material (PIM-NIM-PIM) channels. Based on the linear stability analysis, an analytical dispersion relation is derived and the main characteristics of MI gain are analyzed for both anomalous and normal dispersion instances. The results allow us to evaluate the MI gain in the presence of higher-order dispersion coefficients. Moreover, the influence of self-steepening, intrapulse Raman scattering, second-order nonlinear dispersion (SOND, characterized by (S_{j+3})) and modified saturable nonlinearity on MI gain spectra is discussed. More specifically, it is found that the instability gain in the PIM-NIM-PIM triple-core coupler is crucially enhanced by the combined impact of FOD and system parameters. In the normal GVD regime, a negative FOD coefficient ((beta _4 < 0)) imposes a threshold on the MI gain spectrum with respect to the ratio (f) and tends to suppress and strongly perturb the instability bands, whereas a positive (beta _4 >0) allows MI to persist across all (f). In the anomalous GVD regime, the MI gain develops predominantly under the condition (beta _4 S_{j+3} < 0), while (beta _4 S_{j+3} > 0) suppresses MI. Understanding fourth-order dispersion effects in triple-core couplers directly informs the design and optimization of high-speed, high-power, and ultra-broadband optical devices, ensuring better control over pulse dynamics, spectral properties, and nonlinear interactions in advanced photonic systems.

Herein, for the first time, we report the generation and direct dark-field imaging of photonic jets (PJs) of single dielectric microspheres illuminated by evanescent waves generated using narrow and broadband radiation from a supercontinuum source. The evanescent waves are generated on the surface of a prism by creating the total internal reflection of light within it. The images are recorded by varying the radius of the microspheres, ranging from 10 to 18 μm. The experimental images obtained with supercontinuum, blue, green, and red light are compared. The length and width of the PJs are found in the order of micrometers due to the large size of the microspheres. The proposed technique is simple and efficient in visualizing PJs, allowing for the simultaneous estimation of their length and width. It can also allow us to visualize the photonic nanojets, which have dimensions in the order of nanometers, usually generated from single tiny dielectric microspheres under evanescent illumination. For comparison, the theoretical simulations are performed on the PJs generated from single dielectric microspheres under non-evanescent (direct) illumination. Finally, the possible applications of the PJs generated by evanescent waves in different microscopy systems are reported here.

This study provides a detailed investigation into the structural, electronic, optical, and photovoltaic properties of the lead-free double perovskite Cs₂NaBiI₆ by integrating DFT, multi-platform device simulations (SCAPS-1D, wxAMPS, and COMSOL), and data-driven machine learning modeling. DFT calculations confirm a stable cubic Fm̅₃m phase with a lattice constant of 12.586 Å, and energy bandgap of 2.20 eV, indicating strong optical absorption in the visible region. The electronic band analysis reveals a lighter electron effective mass (mₑ = 0.617 m₀) and higher mobility (u_n = 28.5 cm²/V·s) compared with that of holes (mₕ = 1.26 m_o, u_h = 14.0 cm²/V·s), confirming electron-dominated transport. The effective density of states at 300 K was found to be Nc = 1.21 × 10¹⁹ cm⁻³ and Nv = 3.54 × 10¹⁹ cm⁻³. SCAPS-1D device simulation of the optimized AZO/Cs₂NaBiI₆/CuI configuration achieved a power conversion efficiency (PCE) of 23.31% with Voc = 1.23 V, Jsc = 21.80 mA/cm², and fill factor (FF) = 86.63%. Further optimization of the absorber thickness (800 nm), defect density (10¹⁵ cm⁻³), and interface parameters resulted in an efficiency enhancement of 25.22%. Cross-validation with wxAMPS and COMSOL showed excellent agreement, confirming the model’s robustness. Machine learning-based regression models (Linear, SVM, Random Forest, and XGBoost) were trained on simulation datasets; XGBoost achieved superior accuracy (R² ≈0.9993, MSE = 0.010) for PCE prediction. Feature-importance analysis identified defect density, doping concentration, and active layer thickness as the most critical determinants of PV performance. These combined theoretical, simulation, and machine learning findings establish Cs₂NaBiI₆ as a high-potential, and environmentally benign material for next-generation PSCs.

This paper proposes a graphene-based absorbing metasurface operating in the terahertz (THz) range, featuring switchable and tunable frequency bands. By applying a bias voltage to adjust the Fermi level of graphene, two distinct operating states can be achieved. When E_f = 1.1 eV, the absorption exceeds 90% within 2.8–8.7 THz; when E_f = 0.08 eV, strong absorption persists across 0.1–4.1 THz. In both frequency bands, the metasurface exhibits good impedance matching with free space. Furthermore, analysis using the phase cancellation metric confirms that the asymmetric configuration of the dielectric substrate is a key factor for broadband impedance matching. Based on the Drude model of graphene and the dispersion relation of surface waves, the observed blue shift in absorption with varying Fermi levels is explained.The metasurface maintains high absorption for both TE and TM waves under wide incident angles at E_f = 1.1 eV and E_f = 0.08 eV, achieving efficient absorption even at an incident angle of 60°. It also shows polarization insensitivity. The absorption mechanisms under the two operating states are analyzed using the equivalent circuit model and multiple interference theory, respectively, and the results are consistent with the simulations.The electric and magnetic field distributions further clarify the mechanism behind the efficient broadband absorption. In terms of fabrication and experimental design, reasonable improvements have been made based on existing strategies. Finally, a comparison with previous works demonstrates that the proposed metasurface achieves an integrated capability of dual-band switchability, tunability, and ultra-broadband absorption, showing great potential for applications in THz electromagnetic shielding, communication, and related fields.

Thanks to nonlinear effects, focusing, filtering, waveguide coupling, field enhancement, and other high degrees of optical tunability, resonant waveguide grating (RWG) has a broad scope of applications in science and industry, such as in solar cells, photodetectors, polarizers, spectrometers, filters, and biosensors. For field enhancement ability on the surface of RWGs for bioimaging and biosensing applications, a diverse range of parameters affect the electronic field distribution on the surface of RWGs, such as depth and period of grating, materials used to fabricate the grating, thickness, and refractive index of the layers around the grating. This research focuses on investigating the refractive index dependence of the resonance angle and the average value of the magnitude square of the electric field on the surface of the grating based on a simulation method. After optimizing the refractive index, an experiment was conducted to synthesize RWG and the real system, utilizing a grating to measure transmission and achieve good transmittance results.

Quantum Key Distribution (QKD) uses the principles of quantum mechanics to establish secure cryptographic keys among two or more parties. It includes encoding of the quantum state with the help of a quantum detector and quantum operations. Many QKD protocols have been developed to allow safe key establishment between two parties BB84, E91, etc. However, multiparty QKD is still remains a challenge due to the inherent principle of quantum mechanics like entanglement and observation. This paper puts a step ahead to establish a three-party QKD protocol that allows secure key establishment within a network. The proposed model is a closed three-party network architecture that uses the theory of bilocality. The model comprises three independent sources that share entangled particles with adjacent neighbors. The proposed QKD protocol provides a secret key distribution when measured with suitable observables and has potential applications like military operations that involve secure communication. The quantum bit error rate (QBER) and key generation rate guarantee efficient key establishment and security against eavesdropping in the network.

Optical intelligent reflecting surfaces (IRS) represent a breakthrough technology for enhancing free-space optical (FSO) communication flexibility and coverage. However, inherent optical signal characteristics render these systems critically vulnerable to malicious jamming, demanding robust resilience analysis. This work conducts a comprehensive jamming impact analysis under two practical scenarios: destination-directed and IRS-directed jamming. We develop novel channel models capturing the combined effects of path loss, atmospheric turbulence, pointing errors, and angle-of-arrival fluctuations. Closed-form expressions for the average bit error rate and outage probability are established for both intensity modulation/direct detection and heterodyne detection schemes. Asymptotic analyses reveal the diversity order and coding gain in high signal-to-noise ratio regimes. Monte Carlo validations demonstrate how jamming active probability, atmospheric conditions, and geometric alignment fundamentally govern system security. This study delivers essential design guidelines for optimizing IRS-assisted FSO systems against evolving jamming threats.

The source of terahertz (THz) radiation upon exposure of wide-bandgap semiconductors to femtosecond laser pulses in a magnetic field is photoexcited electrons. It is shown that a quantitative description of THz pulses generation can be achieved using confluent Heun functions. The electric field strength and total energy of THz pulse have been found for an arbitrary ratio of the size of photoexcited electron localization region to the characteristic wavelength of generated radiation. Numerical calculations of the field strength at the sample surface and the total energy have been performed for GaAs.