In this work, we present a polarization‐sensitive imaging photodetector based on a PdSe 2 /MoS 2 van der Waals heterojunction. Capitalizing on the strong anisotropic optoelectronic characteristics of the heterostructure, the device exhibits exceptional polarization‐resolved imaging capabilities across the visible to near‐infrared spectrum. It achieves a high polarization extinction ratio of 3.64 at 532 nm, enabling precise polarization discrimination in imaging applications. The detector further demonstrates robust performance in polarization‐based contrast enhancement and scene analysis. These results underscore the significant potential of the PdSe 2 /MoS 2 heterojunction for next‐generation polarization‐sensitive imaging systems operating in broad spectral ranges.
A compact hybrid graphene–VO2 terahertz (THz) bandpass filter integrating reconfigurable operation, differential biosensing, and machine learning (ML)–based prediction is proposed and numerically investigated. The device consists of a symmetric dual-stepped-impedance resonator (SIR) fabricated on a quartz/silicon substrate, where graphene provides electrical tunability and a VO2 phase-change layer enables dynamic modulation. Three independent tuning approaches are demonstrated: geometric control through SIR dimensions, graphene chemical potential variation (0.0–1.0 eV), and VO2 conductivity switching (200 − 2 × 105 S/m). These mechanisms enable broadband frequency reconfiguration from 0.82 to 2.47 THz, achieving a tuning ratio of 3.01:1. For sensing applications, the differential resonator configuration provides self-referenced operation, delivering a maximum refractive index sensitivity of 412 GHz/RIU and a figure of merit of 8.24 RIU−1. Hemoglobin detection is demonstrated over clinically relevant concentrations (0–160 g/L) with a detection limit of 4.2 g/L. Furthermore, six ML models trained on 15,000 physics-informed synthetic samples are evaluated for analyte prediction. Gradient boosting provides superior performance with an R2 value of 0.9971, RMSE of 0.0061 RIU, and MAE of 0.0044 RIU. Random forest classification achieves 98.7% accuracy in identifying VO2 phase states. The proposed graphene–VO2 platform offers a versatile solution for biomedical sensing, environmental monitoring, and adaptive THz communication systems.
We find that considering the transverse effect, the intensity output of the ring-cavity laser can exhibit new dynamical characteristics, with its output evolution presenting symmetrized laser pattern. Moreover, it is highly sensitive to the initial value assigned to the system. On this basis, we further investigate the issue of remote synchronization transmission of signal using the ring-cavity laser with transverse effect. In the designed synchronization transmission strategy, there is no need to design a complex Lyapunov function, but rather to adjust the parameter to achieve the synchronization transmission of the signal, which greatly improves practicality.
An optical fiber sensor with a Fabry–Perot cavity is described, in which a polydimethylsiloxane layer is bounded by two aluminum mirrors at the end of an optical fiber. The interference response of the sensor was evaluated in both the spectral and time domains. For the fabricated sensor, interference fringes with a visibility of ∼14 dB were achieved in air in the spectral domain at a final cavity length of ∼34 μm. The sensor was tested in acetone vapor and in liquid carvone, where a significant red shift of the interference fringes was observed in the spectral domain, along with different swelling/deswelling dynamics in the time domain. The sensor configuration is compact and reusable, and its parameters can be readily optimized for different target analytes and environments.
This paper employed the pulsed laser deposition (PLD) technique to synthesize InGaN/porous silicon (InGaN/Psi). The Psi was synthesized by the laser-assisted photoelectrochemical etching (LAPECE) method. The thin film is synthesized using three wavelengths: 1064, 532, and 355 nm. The structural, morphological, and topographical properties of the films were systematically analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and energy-dispersive X-ray spectroscopy (EDX). The results show that shorter laser wavelengths (355 nm) enhance pore filling and improve film uniformity. The sample deposited using a laser wavelength of 355 nm exhibited the highest XRD peak intensity for InGaN. This makes InGaN/Psi a viable heterostructure for optoelectronic applications. Sample deposited using a laser wavelength of 355 nm exhibited the highest XRD peak intensity for InGaN.
Trace gas real-time detection in severe environments has been a challenge for traditional sensors. In this study, an infrared gas detection system has been developed for dangerous gas detection including CO and CH4. The detection system consists of a standalone instrument and a nonreflective gas cell which is linked with the instrument by optical fibre. The instrument has optical parts and self-developed electrical parts including laser driver circuit, laser temperature control circuit, digital lock-in amplifier circuit, and linear power circuit. The gas cell is mounted on a parallel biped walking robot which is designed for deploying in dangerous areas in order to perform tasks such as fire-fighting, transporting materials, or rescuing. Based on the TDLAS-WMS technique, there are two laser diodes whose centre wavelength is around 1563 nm and 1654 nm adopted in the proposed detection system. The absorption line of CO and CH4 can be scanned across by tuning the wavelength of DFB laser periodically in order to obtain the real-time concentration. Spectroscopy tests demonstrate the effectiveness of the laser driver circuit which involves updated hardware. The proposed parallel biped robot has been optimized to achieve stable walking posture. Gas detection experiments show that the sensing fluctuation is 0.59% by using the target gas at 2 & times; 104 ppm. Experimental results demonstrate the effectiveness and stability of the proposed system.
The ultrasensitive detection of ionic species is of critical importance for environmental monitoring, biomedical diagnostics, and industrial analysis, yet remains challenging due to the limitations of conventional sensing platforms. In recent years, MXene quantum dots (MQDs) have emerged as a new class of luminescent nanomaterials that uniquely bridge electrochemistry and photophysics. Owing to their quantum-confined dimensions, rich surface chemistry, and intrinsic electrical conductivity, MQDs simultaneously support electrochemiluminescent (ECL) and fluorescent (FL) emission, enabling dual-mode ion sensing within a single material platform. This review provides a comprehensive overview of the fundamental mechanisms governing ECL and FL in MQDs, with particular emphasis on the roles of surface states, defect chemistry, and charge transfer pathways. Advanced nanocomposite and interfacial engineering strategies designed to enhance stability, signal amplification, and selectivity are systematically discussed. Representative applications in ultrasensitive ion detection are compared, highlighting how dual-mode sensing improves analytical reliability and robustness in complex matrices. Finally, emerging trends toward coupled ECL–FL intelligence, system-level stability, and real-world deployability are outlined. By unifying mechanistic insight with materials engineering and sensing performance, this review aims to guide the rational design of next-generation MQD-based ion-sensing platforms.
The present work analyzes the effect of Cu alloying in ZnO on the optical and structural properties of ZnO:Cu (CZO) thin films deposited by the pulsed spray-pyrolysis technique from molecular solutions. The study used XRD, SEM, EDX, Raman spectroscopy, and optical spectroscopy. The films are single-phase, with a hexagonal wurtzite structure, and do not contain secondary phases, as confirmed by XRD and Raman spectroscopy. EDX analysis confirmed the effective incorporation of Cu atoms into the ZnO crystal lattice. The bandgap width changes insignificantly upon alloying, remaining within the range of 3.32-3.33 eV. The analysis of the Urbach energy EU revealed an overall tendency to increase with increasing Cu content. With increasing Cu concentration, the film thickness decreases, accompanied by a reduction in the refractive index n in the long-wavelength region from 1.58 to 1.51 at lambda = 598 nm. The extinction coefficient k increases from 0.0062 to 0.015 with increasing Cu content, and the parameters n, k, epsilon 1, and epsilon 2 demonstrate a consistent variation with increasing alloying level. The results demonstrate the possibility of controlling the structural and optical properties of ZnO films through precisely controlled copper alloying, opening the way for their potential application in optoelectronic devices and photovoltaic systems, thereby contributing to the development of clean energy technologies and improved energy efficiency.
In this study, we present a novel method to enhance the resolution of fluorescence optical microscopy based on a fluorescence emission difference configuration. In the first stage, a subtraction technique with a small number of subtraction coefficients is introduced to improve spatial resolution while minimizing the occurrence of negative intensity values, thereby preserving image information consistent with the imaging characteristics of the optical system. Subsequently, an image processing procedure is developed based on the optical transfer properties of the system to further enhance image resolution. Both simulation and experimental results demonstrate that the proposed method not only achieves a significant improvement in image resolution but also effectively reduces the loss of information commonly observed in conventional subtraction-based approaches.
Electro-optic modulators based on thin-film lithium niobate (TFLN) are pivotal components in microwave photonic systems. A sunken electrode structure is proposed in this work to improve the device performance. Systematic simulations of the modulator's modulation efficiency and RF characteristics were conducted using the finite element method. Simulation results demonstrate a half-wave voltage-length product (V pi & centerdot;L) of 2.11 V & centerdot;cm, an optical absorption loss as low as 0.03 dB/cm, and a modulation bandwidth of over 100 GHz. Experimental characterization of the fabricated device revealed a V pi & centerdot;L of 2.66 V & centerdot;cm and a modulation bandwidth that significantly surpasses 40 GHz. A comparative analysis with conventional traveling-wave electrode structures confirms that the proposed sunken electrode structure significantly reduces optical absorption loss while preserving excellent modulation efficiency and high-frequency performance. This provides a new approach for subsequent related research and device design.
In order to meet the urgent demand for high-speed and high-capacity data transmission in machine learning, large-scale simulation, high-performance computing, etc., we design and demonstrate an optical transceiver microsystem based on digital prototyping and optoelectronic collaborative simulation. Firstly, based on its architecture and fabrication process, we constructed a parameterized model of the optical transceiver microsystem, which is the digital prototype. The digital prototype is composed of the laser model, modulator model, photodetector model, modulator-driver model, transimpedance-amplifier model, and power-supply model. All the device models are precise and have been revised by measured data. Using this digital prototype, we simulated the signal-transmission characteristics and bit error rate (BER) of the optical transceiver microsystem. Through the digital verification of the digital prototype, high-cost experiments and fabrication processes can be avoided. Besides, defects in the design scheme can be found early and optimized, thereby guiding the development of the actual optical transceiver microsystems. In order to verify the effectiveness of the digital prototype, we carried out fabrication and optoelectronic integrated packaging of the optical transceiver microsystem. Besides, performance tests were conducted on the developed optical transceiver microsystem. The measured maximum data transmission rate is 25 Gbps, with a BER of 5.56 & times; 10-5. By comparing simulation and measured data, it can be seen that the simulation results of the digital prototype are relatively close to the test results of the physical prototype, which proves the accuracy of the developed digital prototype. The digital prototype development offers great engineering reference value for the agile development of optical transceiver microsystems.
This work presents an in-depth and unified exposition of the physics, mechanisms, and emerging trends governing passively mode-locked ultrafast lasers. It systematically reviews the fundamental principles of mode locking, emphasizing the role of both real saturable absorbers—such as SESAMs, quantum dots, and low-dimensional 2D materials—and artificial mechanisms, including nonlinear polarization rotation (NPR). The dynamics of pulse formation are analyzed across distinct dispersion regimes, elucidating the generation and evolution of solitons, dissipative solitons, and similaritons alongside their characteristic energy and duration scaling laws. Practical instabilities, including Q-switching and multipulsing, are critically examined with their physical origins and suppression techniques. Advanced characterization and modeling approaches, such as real-time time-stretch dispersive Fourier transform (TS-DFT) diagnostics and numerical functional mapping, are discussed in relation to pulse stability and evolution. The report further explores next-generation materials like MXenes, perovskites, and quantum-dot-based absorbers, as well as emerging paradigms in machine-learning-assisted cavity optimization and sub-10 fs pulse generation. Overall, this study provides a comprehensive framework linking material engineering, nonlinear dynamics, and laser design strategies, offering insights relevant to the development of high-performance ultrafast sources for spectroscopy, precision machining, biomedical imaging, and optical communications.
This study systematically optimized the geometric parameters of a Soller slit collimator to enhance X-ray detection performance, focusing on maximizing the photon count at the origin (N0) while minimizing the spatial spread, which is defined by the radial distance where the collection efficiency drops to 50% (R50%). Through four sets of finite element method simulations under fixed detector distance (15 mm) and monochromatic X-ray source conditions, the effects of the slit top position (Htop), number of fins (Nf), fin spacing uniformity, and fin height distribution were investigated. The optimal parameters were identified as Htop = 2 mm, Nf = 21, uniform fin spacing (df = 0.5 mm), and uniform fin height (13 mm). This configuration achieved N0 = 178,257 photons, R50% = 34.5 mu m (X-direction), and R50% = 150 mu m (Z-direction), effectively balancing the inherent trade-off between the photon collection efficiency and spatial resolution. Compared to the optimal design, configurations employing nonuniform spacing and nonflat height distributions degraded spatial resolution by 12%-19%. The optimized design shows significant potential for improving spatial resolution in microfluorescence applications within synchrotron radiation beamlines. Placing the sample surface near R50% can effectively reduce the influence of scattering signals within the bulk material. This can serve as a low-cost alternative for confocal experiments.
A novel hexagonal photonic crystal fiber (PCF) design with broadband dispersion control has been proposed for use in optical communication systems. By optimizing a 1.7-mu m hole diameter and 2.60-mu m pitch, the PCF achieves near-zero flattened dispersion from 1400 nm to 1800 nm, with dispersion ranging between +0.608 and 0.085 ps/km/nm up to 2000 nm, including +0.33 to -0.72 ps/km/nm in the 1400-1600-nm band. The design also offers a large effective mode area at 1.5 mu m, thereby reducing nonlinear effects while simplifying the modeling complexity commonly found in microstructured fibers. The proposed PCF demonstrates significant potential for applications in high-capacity optical networks, nonlinear optics, and advanced dispersion management systems, contributing to the development of next-generation optical fiber technologies.
Interferenceless coded aperture correlation holographic (ICOACH) is a newly proposed nonscanning, wide-spectrum, 3D wide-field imaging technique for incoherent illumination in recent years and has demonstrated the potential for sizable applications in a variety of imaging fields. In this paper, we propose a super-resolution imaging of the ICOACH (SR-ICOACH) system with structural illumination. In SR-ICOACH, structured light with different phase shifts of a certain space frequency illuminates the object to realize the encoding of the high-frequency information of the object, and an annular sparse phase mask further modulates the object light information and records a single exposure object hologram (OH). Point spread hologram (PSH) of a pinhole is recorded by the regular ICOACH method. Then, the reconstructed image with a high signal-to-noise ratio with structured light fringes is obtained by the correction cross-correlation reconstruction method with PSH and OH. Finally, the super-resolution reconstructed image of the object is obtained by the super-resolution reconstruction method with structured light reconstruction. The simulation results demonstrate the possibility of structured light illumination to improve the resolution of ICOACH imaging. The proposed method further extends the imaging performance of the ICOACH system and provides a new imaging tool for the system to be oriented to high-resolution microimaging and other fields.
The study of the relationship between the shape of an object and the patterns of liquid flowing through them is of great interest in many fields of science and industry. Generally, objects with different geometry will generate different flow map which is related to their shape. A wide variety of methods have been proposed with the goal of detecting object by shapes. In this context, here, we explore and demonstrate the combination of machine learning and laser speckle contrast imaging to classify the shape of an object via liquid flowing through it. In our setup, laser light shines on the flow which passes through four objects of different shapes. The diffused speckle images are acquired by a camera and are converted to flow maps on the computer. These maps are then fed into a convolutional neural network for classification and recognition of the objects. We created a database with experimental flow maps and trained the SqueezeNet model to classify new maps; 70% images were used for training and 30% for validation and testing per object. Through experimental results, we show that the proposed method can successfully classify objects with a high accuracy rate. The findings of this study could, for example, be used to discriminate between different types of prostate cancer, especially where identifying abnormal flow map during urination holds diagnostic value.
Hydrogen sulfide (H 2 S) regulates crucial physiological and pathological processes, and its dysregulation is linked to serious diseases. A sensitive and selective imaging method is essential for detecting endogenous H 2 S in complex biological systems. The probe benzo1‐DCM‐O‐NBD and its product benzo1‐DCM‐OH, derived from π expansion of the DCM‐O‐NBD probe, have been studied for their luminescence mechanisms. Investigations into the effects of various geometric modifications on their optical properties have been conducted. Results of calculation reveal that the introduction of strong electron‐withdrawing substituent groups (F, Cl, Br, and CN) into the benzopyran position of benzo1‐DCM‐OH effectively suppresses molecular skeleton scissoring vibrations and significant geometric relaxations associated with line‐type π expansion, thereby enhancing fluorescence emission. This approach also enhances two‐photon absorption (TPA) ability and spectral resolution. CN‐benzo1‐DCM‐OH particularly exhibits excellent two‐photon fluorescence properties. These studies have led to the identification of potential materials for biological imaging and H 2 S detection that provide easily distinguishable spectra (with a Stokes shift of up to 85.43 nm), improved luminous efficiency (14.1%), and a larger effective TPA cross section (295 GM at 950 nm). This research provides a more detailed theoretical framework for the design of novel two‐photon excited fluorescent probes.
This paper presents a double-negative metamaterial absorber (MMA) based on a cross-connected square-ring resonator, which combines a square ring with four orthogonal rectangular arms. The proposed symmetric design has significantly improved field localization and enables dual-band absorption at 1.4 and 4.1 THz having absorption of 99.67% and 99.93%, respectively, making it suitable for polarization insensitive biosensing. The absorber is built on a polyimide substrate with silver layers on both sides, and the overall dimensions are 0.205 lambda x 0.205 lambda x 0.015 lambda. The proposed MMA shows strong sensitivity to refractive index changes, distinguishing between prostate cancer cells (n = 1.398) and normal prostate cell (n = 1.30). The calculated sensitivities are 2530 and 2875 GHz/RIU at the two frequencies, with figure of merit (FOM) of 78.13 and 57.5 and Q-factor of 41.57 and 81.8, respectively. Parametric studies including H-field, surface current distributing, and substrate variations are conducted to understand the absorber's behavior. Furthermore, an equivalent circuit is proposed, to confirm a good agreement with computer simulation technology (CST) simulation result. To improve the predictability, a machine learning (ML) framework has been employed considering five advanced algorithm models including three test scenarios. Among all the results, the extra-trees regressor (ETR) gave the most stable and precise predictions, attaining a validation accuracy of 99.78%.
This work presents a systematic investigation of the sensing sensitivity across various thin-film lithium niobate on insulator (LNOI) waveguide architectures, encompassing strip, suspended strip, slot, and suspended slot configurations. A quantitative comparative analysis of the sensing sensitivity is performed for each waveguide structure, with particular emphasis on the enhanced light-matter interaction and improved sensitivity offered by suspended configurations. Utilizing the suspended slot waveguide design, a loop-terminated Mach-Zehnder interferometer (LT-MZI) refractive index sensor is developed and optimized to realize high-performance sensing. The proposed sensor exhibits a sensitivity of 3662 nm/RIU and a figure of merit (FOM) of 225 RIU-1, indicating strong potential for applications in biochemical sensing and environmental monitoring. These findings offer valuable guidance for the design and optimization of LNOI-based photonic sensors, contributing to the advancement of integrated photonic sensing technologies.
A novel hollow-core antiresonant fiber with negative curvature fourfold semitube (NCFST) is proposed. It has the advantages of simple structure and fourfold rotational symmetry. The confinement loss of NCFST is less than 0.03 dB/km in the wavelength range of 1.3-1.7 mu m and only 0.0165 dB/km at 1.55 mu m. Meanwhile, the ratio between minimum higher-order mode loss (Min HOM loss) and fundamental mode loss (FM loss) can reach 41,000, which shows excellent single-mode operation. Moreover, the effect of the ellipticity of the antiresonance element on confinement loss is analyzed in detail. Our numerical study shows the ellipticity of the inner tube has little effect on the transmission loss and single-mode characteristics of the fibers. In the analysis of manufacturing tolerances, the influence of the wall thickness of the suspended glass layer and the deformation of the inner tube on fiber properties is also discussed.
