Optical and Quantum Electronics最新文献

A dual-band graphene-based plasmonic bandpass filter with hybrid post-fabrication tunability is presented for terahertz (THz) networks. The proposed structure consists of a graphene nanoribbon waveguide coupled to two sets of branched resonant stubs placed on a silica substrate and covered with an azo-dye-doped liquid crystal (LC) layer. In the designed structure post-fabrication hybrid tunability is achieved by two elements which are electrical control via graphene chemical potential and all-optical control through laser-induced reorientation of LC molecules. Numerical simulations show two controllable passbands centered near 2 THz and 5.75 THz accompanied by deep reflection minima below − 33 dB. The all-optical tuning method enables continuous frequency reconfiguration by modifying the effective permittivity of the LC layer, while electrical gating provides a complementary tuning channel through carrier-density modulation in graphene. An analytical model based on the transmission-line method (TLM) is developed by the electrostatic scaling law (ESL) to validate the full-wave results and provide physical insight. The analytical predictions show excellent agreement with full-wave simulations, with frequency deviations below 5%. The loaded quality factors are extracted as 20 and 31 for the lower and upper bands, respectively. Owing to its compact footprint (350 nm × 420 nm), dual-band operation, and independent hybrid tunability, the proposed filter is a strong candidate for reconfigurable integrated THz plasmonic systems.

Halide perovskites have been getting much attention because of their impressive power conversion ability, allowing them to pursue entirely inorganic lead-free perovskites to achieve better solar performance without lead toxicity. The Physical properties of Cs₂XInCl₆ have been carried out using DFT-based calculations verified the stability with formation energy of -3.9 eV for Cs₂SnInCl₆ and − 1.8 eV for Cs₂BiInCl₆,respectively. The phonon dispersion analysis verifies the dynamical stability of systems by fundamental modes in the phonon spectrum. The band gap of the investigated material was tuned for use in renewable energy devices from 2.7 eV to 1.8 eV by applying modified Becke Jhonson (mBJ) and Spin orbit coupling (SOC) due to strongly correlated electrons system. The optical characteristics have been studied for optoelectronic purposes, including optical loss factor, optical conductivity, absorption, refraction, and dielectric constant. The ductility is demonstrated by high bulk-to-shear modulus ratios and positive Cauchy pressures of fracture toughness, demonstrating that Bi-based materials provide more resistance to crack propagation, indicating that it is appropriate for mechanically demanding applications. Thermoelectric computations show high Seebeck coefficients of 3.1 µV/K, power factors of 4 to 12.0 m.W/mK²s, and figure-of-merit (ZT) (0.8) at temperatures (600 K). These properties indicate that both compounds are encouraging for thermoelectric and in UV/visible optoelectronic devices.

The Pursuit of prospective materials for efficient hydrogen storage remains an inherent challenge for the scientific community. Perovskite hydrides gained considerable focus because of flexible composition, unique chemical and electronic behavior of hydrides ions. In this study, DFT calculations within the CASTEP framework using PBE-GGA and HSE03 functionals were employed to investigate the geometrical, electronic, optical, magnetic, mechanical, bond population, and hydrogen storage properties of AWH₃ (A = Li, Na, K, and Cs) perovskite hydrides. These perovskites exhibit stable cubic structure and metallic character. Magnetically, all compounds reveal antiferromagnetic tendencies coupled with anisotropic and rigid behavior. Among the considered materials, LiWH₃ demonstrates highest thermodynamic stability (F.E = − 4.47 eV) supported by phonon dispersion analysis. The hydrogen storage capacity (1.56 wt %), whereas CsWH₃ exhibits the lowest values (F.E = − 2.53 eV, 0.95 wt %). From elastic constants (C₁₁, C₁₂, and C₄₄), all compounds meet the born stability criteria, further confirmed the mechanical stability. Additionally, Poisson’s ratio (ν), Pugh’s ratio (B/G) ratio, and anisotropic factor indicate that all compounds exhibit ductile and anisotropic character, with NaWH₃ standing out as the most ductile, along with superior values for Young’s modulus and shear modulus, signifying greater rigidity compared to LiWH₃, CsWH_3, and KWH₃. In terms of optical performance, LiWH₃ exhibits significant optical conductivity and absorption in the low-energy region, along with enhanced reflectivity and refractive index at 0 eV. Mulliken atomic and bond populations, effective valance, as well as charge density expose the complex bonding characteristics. The analysed properties proposed that LiWH₃ stands out as the most promising candidate, outperformed in terms of stability, hydrogen storage capacity, and overall efficiency as compared to other AWH₃ (A = Cs, Na, K) perovskite hydrides.

The performance of high-speed optical communication systems is constrained by Chromatic Dispersion (CD), which poses a significant challenge to data transmission integrity. This paper proposes a method to mitigate CD using cascaded Apodized Fiber Bragg Gratings (AFBGs). The apodization function plays a crucial role in dispersion mitigation, effectively reducing side lobes in the Fiber Bragg Grating (FBG) reflection spectrum. The proposed model employs two cascaded stages, each utilizing an apodization function that merges the Nuttall and Bartlett profiles. This model is investigated to enhance FBG performance and is compared with other apodization functions. Using an induced refractive index of 2.8 × 10⁻⁵ and a grating length of 60 mm, numerical results show that the Nuttall-Bartlett apodization function achieves the narrowest Full Width at Half Maximum (FWHM) of 0.027 nm—a 20.48% improvement over the uniform model—while maintaining a reflectivity of 99.12%. The performance of the proposed model is further evaluated through the quality factor (Q-factor) and Bit Error Rate (BER), yielding an improvement in both metrics over the uniform model.

CdTe thin film photodetectors and CdTe/Si heterojunction photodetectors were fabricated by using PLD system. CdTe thin films were grown by increasing the amount of applied laser pulses. The surface morphology, crystal structure and optical characterization were investigated. The higher in the laser pulse number or energy cause the particle size to expand and the thin film thickness to increase and the band gap to decrease. In addition, the atomic weight ratio of Cd increased and that of Te decreased with the augment in the laser pulses number. CdTe thin film and CdTe/Si heterojunction materials exhibited photodetector properties under the 1sun of 100 mW/cm². The photosensitivity, responsivity, detectivity and photocurrent gain of the photodetectors were calculated based on the opto-electronical measurements under 100 mW/cm². The photodetector performance of CdTe/Si heterojunctions has been demonstrated to outperform that of CdTe thin films, exhibiting superior characteristics in terms of photosensitivity, responsivity, detectivity and photocurrent gain. In the crystalline characterization, XRD analysis revealed that all CdTe films were polycrystalline with mixed cubic and hexagonal phases, with grain size increasing and dislocation density decreasing as thickness grew. Based on the obtained SEM and AFM images it can be said that there are particle coalescence and island-like surface structures at higher thicknesses, directly proportional with the roughness. These findings demonstrate that CdTe thin films and CdTe/Si heterojunctions produced by employing PLD technique offer a simple pathway to tune optoelectronic properties, with heterojunction devices showing particular promise for future high-performance photodetectors.

This work presents a Python-based numerical simulation framework for integrated quantum photonic systems governed by the nonlinear Schrödinger equation (NLSE). The study models excitation, guided propagation, and detection of femtosecond optical pulses in chip-scale waveguides using the split-step Fourier method. To ensure both numerical clarity and physical relevance, two parameter regimes are employed: a normalized (dimensionless) formulation for algorithmic validation and envelope stability analysis, and a physically realistic SI-valued formulation for modeling soliton dynamics and broadband nonlinear effects. Input conditions include Gaussian and hyperbolic secant pulse envelopes with central wavelength (lambda _0 = 1550) nm and peak power ranging from 0.5 to 5 W. Representative waveguide lengths of (L = 2) mm are considered with grid resolutions of (Delta z = 0.01) mm and (Delta t = 0.1) fs. In the physical regime, dispersion and nonlinearity are modeled using parameters consistent with experimentally reported platforms, including (beta _2 approx -0.7,textrm{ps}^2/textrm{m}) and (gamma sim 10^2,textrm{W}^{-1},textrm{m}^{-1}). Simulation results demonstrate that low-dispersion regimes preserve temporal and spectral pulse integrity, while anomalous dispersion conditions produce soliton formation and spectral broadening consistent with reported supercontinuum generation in AlGaAs and (hbox {Si}_3{N}_4) waveguides. Transverse mode analysis confirms single-mode confinement, and phase evolution maps reveal coherent phase wrapping essential for quantum interference applications. A probabilistic photodetection model yields normalized detection rates consistent with experimentally reported efficiencies of InGaAs SPADs and superconducting nanowire single-photon detectors. The proposed framework provides an experimentally consistent and extensible NLSE-based simulation pipeline, supporting the co-design and optimization of nonlinear integrated photonic circuits for quantum information processing.

This paper presents a simple signal processing procedure to enhance the performance of a free-space laser speckle-based salinity sensor system. The experimental setup comprises a cylindrical glass vessel containing the liquid sample of interest, which is probed by a light beam formed by merging two laser beams of different wavelengths. The mixed laser beam produces a speckle pattern that provides quantitative information on the sample concentration by correlation coefficient determination. The definition of a multiplicative fusion function, which involves the multiplication of the measured correlation coefficients for each two wavelengths, enhances the sensor’s sensitivity compared to a single-wavelength approach without altering the system noise, thereby increasing the signal-to-noise ratio. The combined product function allows the sensor system to exhibit high linearity at low concentrations, an enlarged output range, a salinity sensitivity of -0.853 /%, which is significantly higher than that reported for fiber optic speckle-based salinity sensors, and a limit of detection comparable to that offered by state-of-the-art, more complex, interferometer-based optical fiber salinity sensors.

This paper presents a high-capacity, compact chipless graphene tag for terahertz identification (THID) within the 2–7 THz range, using polarization-orthogonal encoding. The tag features graphene strip resonators embedded on a low-loss TOPAS substrate, with a gold ground plane. Independent responses to transverse electric/ transverse magnetic (TE/TM) fields are achieved by tuning the graphene’s impedance through chemical potential gating, µ_c. A single-bit tag with logic (0)/(1) using µ_c = 0/0.8 eV reaches a peak absorption of 5/99.9% at 3.29 THz with ultranarrow linewidths for TM-polarized waves and zero TE crosstalk, maintaining over 84% efficiency under oblique incidence up to 75°. Seven-bit linearly polarized (LP) tag configurations are designed by cascading graphene strips (lengths 2.4–7.5 μm, 0.52 THz spacing). LP tags cascaded in series with different chemical potentials are designed for 7-bit, 14-bit, and 21-bit encoding. Dual-polarized orthogonal encoding doubles the spectral capacity by providing independent TE/TM responses in both single- and multi-layer configurations, supporting 7-bit and 14-bit per polarization. Single-layer orthogonal tag designs enable 11–14 bits with distinct TE/TM peaks (77% – 100% absorption) through gating tuning. Finally, symmetrical multi-layer designs (1.5 μm dielectric separation, µ_c = 0, 0.8, and 0.9 eV) achieve 14/28-bit dual-polarized capacity (7/14 bits per polarization) across the frequency range of 2.72–4.14 THz, with 80% – 100% absorption efficiency for structures with two to four layers.

We investigate the role of local Gaussian operations, specifically local displacement operations (LDOs) and local squeezing operations (LSOs), in enhancing the phase sensitivity of a Mach–Zehnder interferometer (MZI). We consider both single-arm and dual-arm implementations of these operations and analyze the resulting phase sensitivity and quantum Cramér–Rao bound (QCRB) using coherent and squeezed vacuum inputs under homodyne detection, for both ideal and lossy conditions. We show that, under appropriate assumptions on the displacement parameters, single-arm and dual-arm LDO schemes yield identical phase sensitivity, indicating that a single-arm implementation is sufficient for displacement-assisted enhancement. In contrast, for local squeezing operations, the dual-arm LSO scheme consistently outperforms its single-arm counterpart under corresponding assumptions on the squeezing parameters. We further demonstrate that both LDO and LSO schemes improve robustness against photon loss and lead to a reduced QCRB in both ideal and lossy scenarios. Our results highlight local Gaussian operations as experimentally feasible, low-cost tools for enhancing phase sensitivity and loss robustness in quantum optical interferometry, within the considered framework.

Graphitic carbon nitride (g-C₃N₄), a promising two-dimensional (2D) semiconductor, holds great potential for optoelectronic applications but suffers from poor electron–hole separation and limited carrier diffusion. To overcome these limitations, S-doped g-C₃N₄ samples with varying sulfur concentrations (2, 4, and 6 wt%) were synthesized to enhance light absorption and charge transport. Structural characterization using XRD, FTIR, and FESEM confirmed the successful incorporation of sulfur and improved material properties. Optical and electrical characterizations—including UV–Vis, photoluminescence, EIS spectroscopy, Mott–Schottky analysis, and photocurrent measurements—revealed that the gCN(4 S%) sample exhibited the highest photocurrent, attributed to enhanced light absorption, increased charge carrier density, and reduced trap site. The EIS analysis showed the smallest Nyquist semicircle for gCN(4 S%), indicating efficient electron–hole separation and improved conductivity. Furthermore, photodetector performance metrics—including photoresponsivity (206.88 mA/W), specific detectivity (6.2161 × 10¹⁰ Jones), photosensitivity (5060), and external quantum efficiency (950%)—were significantly enhanced in gCN(4 S%) compared to undoped and other doped samples. These findings suggest that optimal S-doping substantially improves the optoelectronic performance of g-C₃N₄, making gCN(4 S%) a strong candidate for high-performance photodetector applications.