Optical and Quantum Electronics最新文献

This paper introduces and investigates a graphene and vanadium dioxide based metamaterial absorber in the terahertz region. The proposed structure consists of four layers (gold, dielectric layer, graphene, and VO₂) and is designed using the phase transition properties of VO₂ and the tunability of graphene. Simulation results show that in the insulating phase, the structure operates as a narrowband absorber with distinct absorption peaks, while in the metallic phase, broadband performance with over 80% absorption in the 4.28–7.55 THz range is observed. The structure’s performance was analyzed through the electric field distribution and surface current, and the effects of temperature variations and chemical potential adjustments on the absorption spectrum were studied. A distinguishing feature of this structure is its tunable absorption enabled by temperature and chemical potential changes. The key attributes of this structure, including tunability, sensitivity to temperature changes, and its application in logic gates, make it a suitable candidate for sensing and optical information processing applications in the terahertz region.

This report presents the development and experimental demonstration of a passively high-power Q-switched fiber laser operating at a wavelength of 1940 nm, utilizing MoWS₂ as a saturable absorber (SA). A Q-switched oscillator was constructed using a single-mode thulium-doped fiber (TmDF200) and then to a double-clad thulium-doped fiber (DC-TDF) amplifier stage. The laser system demonstrated in this study showcases a notable average output power of 304 mW, delivering a peak power intensity of 3.11 MW/cm². The pulse energy was 7.96 µJ, while the repetition rate and pulse width were 38.2 kHz and 4.02 µs, respectively. The main amplifier exhibits a commendable slope efficiency of approximately 6.7% and 40 dB signal-to-noise ratio (SNR). The results of this study indicate that MoWS₂ SA can be beneficial for developing robust, stable, high-power Q-switched fiber lasers.

In this paper, a novel PT-symmetric lattice with an elliptical ring structure is proposed in self-focusing Kerr nonlinear media. The existence and transmission properties of solitons in this potential are numerically studied under longitudinal modulation. Unlike non-PT-symmetric cases, the shapes of solitons in this system show quasi-periodic oscillations, and their transmission power fluctuates as well. Interestingly, these solitons’ period and amplitude are influenced by factors such as initial power, potential well depth, and gain-loss coefficients.

By calculating the optical parameters of a silicon nitride nanowaveguide, the supercontinuum spectra generated through the desired waveguide is simulated making use of the generalized nonlinear Schrödinger equation which governs the supercontinuum generation process. The dispersion coefficients for three different values of a structural parameter of the waveguide have been calculated from the reported dispersion profiles of the nanowaveguide. The pulse propagation of a sech-shaped pulse (1 kW, 30 fs) through the waveguide is simulated making use of the fourth-order Runge–Kutta method. Here, the simulated supercontinuum spectra are compared for different values of the chosen geometric parameter. At a specific geometry of the silicon nitride waveguide, an extreme spectral broadening is generated, especially in the infrared region. It can be observed that the generated supercontinuum spectra from the structure with the structural parameter ({ H_2}) equals to 50 nm is broader than the others, which is due to the presence of multiple zero-dispersion wavelengths in its dispersion profile. The generated supercontinuum spectra cover a wavelength range of 1260–5200 nm with a flatness of 30 dB. Furthermore, the soliton dynamics through this supercontinuum process have been discussed.

The current study investigates a numerical method based on exponential cubic B-spline functions to examine the approximate solution of a nonlinear time-fractional gas dynamics equation. The suggested technique employs the usual finite-difference formulation to approximate the Caputo fractional time derivative and exponential B-spline basis functions to interpolate the solution curve along the spatial direction. Stability analysis is provided to ensure that the error does not amplify during the computational process. The uniform convergence of the suggested approach is also discussed. The effectiveness and accuracy of the proposed method are tested through numerical simulations. Graphical and tabular results are exhibited to evaluate the outcomes of the proposed strategy. The major advantage of the suggested scheme is that the algorithm is straightforward to carry out.

The Rytov theory and the new maritime atmospheric spectrum model are used to derive the analytical formula for the Bessel-Gaussian (BG) beam scintillation index in the maritime turbulent environment with weak perturbations in the paraxial approximation. By varying some parameters, such as the wavelength, the inner scale of the turbulence, the spot size and the turbulent intensities, the scintillation index of the BG beam is investigated numerically. The BG beam scintillation index in the Von Karman spectrum is deduced from our work. The design of a wireless optical communication link operating in the maritime atmosphere would benefit from these results.

The proposed study reported a numerical simulation of a surface plasmon resonance (SPR) sensor for pathogen detection using a layered structure that includes a prism, silver (Ag), silicon (Si), selenium (Se), and sensing medium. The materials are selected and arranged along the z-direction with maximum efficiency to improve the sensor’s sensitivity and accuracy. The Ag layer strengthens surface plasmon waves, and the SF11 prism makes it easier for incident light to be efficiently coupled to the plasmonic surface. Through improved performance over the propagation and confinement of the surface plasmons (SPs), the addition of Si and Se layers enhances overall performance. We could assess the sensor’s performance parameters by examining the SPR curves, which provide important details about the sensor’s sensitivity, resonance angle shift, and detection accuracy (DA). Our simulation results show that our multi-layered SPR sensor demonstrates exceptional sensitivity and specificity for pathogen detection, with a maximum sensitivity of 147.68 degree/RIU, a DA of 0.1290 degree⁻¹, and a figure of merit (FoM) of 19.035 RIU⁻¹, which makes it a valuable tool for early infectious illness diagnosis and analysis.

Ag-alloyed Cu(In,Ga)Se₂ (ACIGS) is a promising material for the bottom subcell in tandem solar cell structures, offering a tunable bandgap that spans the optimal range for maximum efficiency; however, the bandgap widening of ACIGS thin films poses a significant challenge in enhancing their photocurrent. This paper investigates the impact of different grading profiles, specifically focusing on the 'hockey stick'/V-like Ga gradient–induced (GGI) profiles, on the performance of thin-film ACIGS cells. To enhance the physical understanding of these grading profiles we have used Silvaco TCAD tools to analyze how these profiles' depths, notch position, and slope affect the power conversion efficiency (PCE). The optimized ACIGS cell achieves a PCE of 25.80%, compared to 23.60% for the reference device. For the tandem configuration, we pair the optimized ACIGS bottom cell (double grading profile) with a perovskite top cell (band gap ~ 1.66 eV), achieving an overall efficiency of 30.26% under AM1.5G illumination. The obtained results highlight the critical role of Ga gradient profiles in enhancing the bottom cell's performance and stability. Additionally, we compare our results with existing studies to evaluate the broader impact of Ga compositional optimization on ACIGS-based solar cells. This work provides valuable insights into advanced grading strategies and helps us understand the physical behaviour of these high-performance tandem solar cells.

In this paper, we examine the Laguerre-Whittaker-Gauss (LWGBs) propagation in a gradient index (GRIN) medium. The Collins integral is used to get the analytical expression of LWGBs across this optical medium. Numerical demonstrations of the intensity characteristics of these beams in a GRIN medium are presented. The findings demonstrate that the gradient index parameter β and the incoming beam parameters m, l, n and (omega_{0}) have an impact on the behavior of the LWGBs. Furthermore, it is demonstrated that when β grows, the period L decreases and the outgoing beam fluctuates regularly with the propagation distance. The findings presented in this study have applications in optical micromanipulation, free-space optical communications, optical control, and optical trapping.

Cu₂O films were electrochemically deposited on FTO glasses, and the simplest solid-state structures were prepared by the formation of silver contact on the surface of Cu₂O film. Addition of europium nitrate to the electrodeposition electrolyte results in a few time increase of the responsivity of FTO/Cu₂O/Ag structures both in the photodiode (without application of an external bias voltage) and photoresistor (with an external bias voltage) operation modes. In particular, in the self-powered mode, the photodetector prepared with the addition of Eu(III) to the electrolyte demonstrates 4-fold increase in the ampere-watt responsivity reaching 6.7 mA/W at 589 nm. At an external bias of 2 V, the ampere-watt responsivity and specific detectivity under 525 nm illumination for the Eu-modified film-based photodetector are 87.2 A/W (18-fold increase) and 3.11∙10¹² cm∙Hz^0.5/W (6-fold increase), respectively. The increase in photosensitivity is explained by the suppression of charge carrier recombination in the films prepared with the addition of europium, which is confirmed by the photoluminescence spectroscopy.

Graphical abstract