The interference caused by clouds and the surrounding environment leads to significant distortions in the atmospheric polarization data over large areas. We propose an atmospheric polarization mode reconstruction method based on non-neighborhood constraints to address this issue. First, this method leverages the fact that the distribution of atmospheric polarization is solely dependent on the position of the Sun during the same measurement to obtain ground truth data affected by interference through the control variable approach. Second, considering the continuous spatial distribution of atmospheric polarization modes, our approach incorporates a non-neighborhood feature restoration module to uncover dependencies between non-neighborhood regions within the atmospheric polarization data. This capability enables the reconstruction of measured atmospheric polarization data even in case of extensive distortion across large areas. Finally, the results of our ablation experiment show that the indicators peak signal-to-noise ratio and structural similarity are increased by 17% and 25% compared with the non-neighborhood constraint module when the cloud area reaches about 60%.

Light intensity and scintillation index changes of the Laguerre-Gaussian (LG) vortex beam propagated in ocean mixed-media are investigated by numerical simulation based on the random media phase screen method. Simulation results show that the spot size of the LG vortex beam will gradually grow as propagation distance increases, and the dark spot area on the central axis of the beam will gradually shrink until it disappears entirely. When the propagation distance increases from 30 m to 100 m, the scintillation index will quickly increase and then gradually stablize, but when the propagation distance is over 100 m, the scintillation index will decrease. The scintillation index will increase with the increase of the propagation distance for LG vortex beams with different wavelengths, regardless of the wavelength value, and the shorter the wavelength, the larger the scintillation index. The greater the mean square temperature dissipation rate, or the greater the temperature-salinity ratio, or the smaller the kinetic energy dissipation rate, the stronger the ocean turbulence, and the larger the scintillation index.

Since cables are the main load-bearing member of cable structures, it is important to assess their service condition, using data from sensors, to ensure the long-term safe operation of the structures. To improve the survival rate of fiber grating sensors and investigate the effect of embedded sensors on the load-bearing performance of finished ties, five sensors are embedded in the center wire groove of each strand. Moreover, the fiber-optic harness is led through the end plug drilling. Three fiber-optic grating type strand specimens are prepared in order to conduct a static load tensioning experiment. The test results show that the sensor survival rate during tensioning is 100%, the cable force monitoring range is up to 80% of the breaking load, and the cable anchoring efficiency factor is more than 97%. By embedding the fiber grating sensor in the center wire and leading it out through the drilling method, the survival rate of the sensor is ensured and reliable monitoring of the axial stress of the cable is achieved. The average load capacity of the finished cable is 821 kN. The finished cable with the sensor embedded in the slot of the center wire of the strand maintains a good load-bearing performance and meets the requirements for engineering applications.

The traditional visible light positioning scheme usually requires at least three light sources. In this study, a system model that integrates mirror reflection is proposed, and a time-frequency combination method is utilized to achieve two-LED positioning. The proposed scheme is based on the time-frequency combination method and received signal strength algorithm. It integrates the specular reflection power of one virtual lamp into the effective positioning power of its corresponding real lamp and separates the other virtual lamp as the third light source for positioning. To separate each signal used for positioning at the receiving end, the receiving end detects the frequency domain signal through a filter, detects the pulse signal from the time domain through time division sampling, and separates the real light from its corresponding virtual light through the arrival time of the pulse signal, thereby achieving the two-LED positioning. The simulation results show that the two-LED positioning schemes based on virtual lights can effectively locate a half-room near the mirror surface. Furthermore, the positioning accuracy shows an upward trend as the distance between the receiver and mirror surface decreases. Additionally, the average positioning error can be reduced to within 12.4 cm by further changing the position of the two lights from the mirror surface.

With the development of optical communication networks, the need for high-performance broadband mode converters has become increasingly urgent. In this study, we propose and experimentally fabricate strongly-modulated phase-shifted helical long-period gratings (HLPGs) inscribed in few mode fibers, which can realize the function of all fiber broadband orbital angular momentum mode converters. The strongly-modulated HLPG could be fabricated in few mode fibers with short lengths by exposing the fibers to high-power CO2 laser. The fabricated mode converter has a large bandwidth, which could be further increased considerably by introducing a phase shift in the grating. The 10-dB bandwidth of the high-order mode conversion is greater than 200 nm, and the second- and third-order orbital angular momentum modes could be directly excited within the broadband wavelength range. Broadband wavelength tuning could be realized by applying torsion and strain to the gratings. The proposed HLPGs inscribed in the few mode fibers can be adopted as mode converters to realize high-order orbital angular momentum mode excitation with a large wavelength range and high conversion efficiency.

This paper presents an investigation of the performance of a reconfigurable intelligent surface (RIS)-assisted free-space optical (FSO)/radio frequency (RF) hybrid system by considering the effect of the cochannel interference problem in the RF link. An RIS is used to address the inability of the RF link to complete line-of-sight communication and thus improve the communication system performance. The FSO link adheres to a double generalized gamma distribution and considers the pointing error effect, while the RF link obeys a Rayleigh distribution. Further, a decode-and-forward protocol is used at the relay node to mitigate noise interference in the transmitted signal. The cumulative distribution function of the end-to-end instantaneous signal-to-noise ratio of the system is then derived; on this basis, the closed formulas for the outage probability and average bit error rate (BER) of the system are derived. The simulation results show that the performance improvement of this system scheme is relatively evident under weak and medium turbulence intensity. Under weak turbulence intensity, the RIS can effectively resist the influence of interference on the RF link, thus improving the system performance.

Polarization-maintaining-ytterbium-doped double-clad fiber of 20 μm diameter core and 400 μm diameter clad size (PM-YDF 20/400 μm) was fabricated using the modified chemical vapor deposition method and solution doping technology. The numerical aperture of the fiber core was 0.062, and the cladding absorption coefficient of the fiber at 976 nm was 1.4 dB/m, as measured using the truncation method. To examine the effectiveness of fiber laser performance, an all-fiber master oscillator power amplifier testing platform was used. The PM-YDF 20/400 μm has a length of 15.3 m, and its bending diameter is 10 cm. Furthermore, a narrow linewidth linearly-polarized laser output of up to 3.008 kW is achieved using a pump power of 4.143 kW at 976 nm. The full width at half maximum linewidth is 0.213 nm, corresponding to a slope efficiency of 75%. At a laser output power of 2.009 kW, the polarization extinction ratio is 16 dB and the beam quality factor is 1.19 and 1.20. Moreover, stimulated Brillouin and Raman effects are effectively suppressed.

Geiger-mode avalanche photon diode (GM-APD) array improving the signal-to-noise ratio (SNR) has been widely concerned in laser communication and photonic radar. However, due to low transmitting power and strong background noise, the SNR is also low in low-photon detection signal processing. In order to solve the problem, we establish a mathematical model of signal processing based on time-domain and spatial-domain convolutional neural network. The model superimposes echo signals of adjacent four frames in the time domain. In the spatial domain, matrix dimension expansion algorithm is used to expand the convolution kernel dimension, and then echo photon signals are extracted through convolutional neural network. The results show that method can effectively extract the echo photon signal from the noise signal and improve the SNR by 4.5 times. This article can provide references for the hundred-kilometer low-photon detection signal processing.

To address the limitations of transmission distance and operational time in ground-based optical fiber and satellite quantum networks, a measurement-device-independent quantum-key-distribution (MDI-QKD) protocol based on photon orbital angular momentum (OAM) encoding with unmanned aerial vehicles (UAVs) as relay platforms is proposed. Leveraging the mobility and controllability of UAVs, a theoretically secure rapid link is established, and the channel robustness is enhanced using photon OAM encoding. By considering factors such as vortex beam expansion and UAV jitter in an analysis, the transmission distance is shown to be affected by state-dependent diffraction (SDD) and pointing errors, thus consequently affecting the key rate. Additionally, the research results indicate that diffraction effects contribute significantly to system performance. Considering both SDD and UAV jitter, the transmission distance can decrease by 58%, which significantly exceeds the effects observed when considering only atmospheric turbulence scattering. This result is used to establish a theoretical model for quantum-key-distribution systems based on UAV relay. This study enhances the comprehensiveness of theoretical analysis and reduces the discrepancy between theoretical analysis and experimental verification, thus providing an important theoretical reference for the development of future UAV-based quantum communication networks.

Based on a Fourier synthesis illuminator, high frequency MEMS(Micro-electro-mechanical system) vibration micromirror is introduced as an illumination field uniformizing device. In addition to the realization of any off-axis illumination modes, the optimized structure can further improve the intensity uniformity of illumination field and the imaging resolution. It has a simple structure and is easy to operate. The Fourier synthesis illumination and uniformizing structure scheme are designed, the simulation model is established, and the experimental device is set up to verify the uniformity effect through imaging method. In addition, the influences of the vibration amplitude and vibration frequency of the MEMS micromirror on the uniformizing effect are analyzed. The uniformity in the selected illumination area can be increased by more than 11%. The Fourier synthesis illumination and field intensity uniformizing method can be applied to the illumination applications in lithography mask inspection.

A mathematical model is established to analyze the impact of positioning error of marker points on the calibration accuracy of mirror units for solar dish concentrators. The effects of individual and coupled positioning errors of three marker points on calibration accuracy are examined, and the maximum allowable positioning error is determined through a bisection method. Furthermore, the influence of different mirror sizes on calibration accuracy is analyzed by introducing the same positioning error in identical initial poses; a relationship between the mirror unit size and maximum allowable positioning error for calibration accuracy is thus revealed. Finally, the influences of different initial poses on calibration accuracy, under the same mirror size and positioning error of the marker points, are examined. The results indicate that the maximum allowable positioning error for calibration accuracy, considering coupled marker points, is 1 mm. Moreover, larger mirror units exhibit less sensitivity to marker point positioning errors. Optimal installation positions for points A and C are found to be close to -0.0087 rad, whereas, for point B, it should be close to 0.0087 rad. The proposed mathematical model for positioning error of marker points and calibration accuracy can be obtained using simulation results, independent of the geometric shape of the reflective mirror, thus reducing implementation costs and facilitating broad application in practical scenarios.

The study presents a method for online measurement of metal droplets during vacuum arc discharge, based on Mie scattering theory. A vacuum arc metal droplet online measurement system is constructed using a 650-nm red laser as the light source and a camera-synchronous control device. The particle size distribution is inverted using a nonindependent mode differential evolution algorithm. The accuracy of the measurement system was validated through experiments with four types of polystyrene latex ball standard particles, showcasing a measurement error within 5%. Further, online measurements of metal droplets were conducted using four different cathode metal materials under varying discharge currents and pulse widths. The findings suggest that for a given metal, alterations in discharge pulse width or discharge current do not remarkably affect the size of the metal droplets. Conversely, under identical discharge current and pulse width conditions, the material of the cathode metal markedly influences the particle size distribution. Specifically, under the same operational conditions, the median sizes of aluminum, iron, titanium, and molybdenum droplets are 1.55, 1.25, 1.15, and 0.75 μm, respectively. These experimental results serve as a valuable reference for further study of the vacuum arc cathode discharge process.

The practical demand for the use of Brillouin optical time-domain reflectors in engineering applications is constantly being raised: how to accurately determine the starting position of strain/temperature change, facilitate rapid repair, save manpower and material costs, especially in complex situations such as underground engineering and underwater engineering that cannot be directly observed, the precise determination of the starting position of frequency shift along the fiber optic line is particularly important. An improvement is made on the algorithm for obtaining spectrum in Brillouin optical time-domain reflectometer based on peak finding algorithm and short-term Fourier transform. A new quadratic peak finding algorithm is proposed, which calculates the starting and ending points of temperature/strain by judging the peak situation in the Brillouin gain spectrum. In the case of a pulse width of 100 ns and a monitoring distance of 1800 m, the positioning error of the starting and ending points of the 50 m temperature range is 0.4 m, achieving a spatial resolution of 1 m at a detection distance of 2000 m. This algorithm improves the accuracy of the Brillouin optical time-domain reflectometer in locating the temperature starting point and length without increasing the computational time and optoelectronic devices. Compared with the Brillouin optical time-domain reflectometer using peak finding algorithm, the Brillouin optical time-domain reflectometer using secondary peak finding algorithm has stronger practicality and higher cost-effectiveness.

A method for measuring and modeling a bidirectional reflection distribution function (BRDF) of the inner surfaces of holes based on endoscope images is proposed, which provides a theoretical basis for hole inner surface defect detection based on machine vision. In this study, an endoscopic imaging reflection model was first established to analyze the relationship between the endoscopic image brightness and its three-dimensional topography. With stainless steel and galvanized threaded holes used as examples, BRDF values of hole inner surfaces were measured by image brightness in the normal direction. Based on the hybrid reflection model, three types of reflection models of the inner surfaces of holes were established. A genetic algorithm was then used to determine the optimal model parameters of different materials and to analyze the model errors. Experimental results show that the inBRDF model based on the Cook-Torrance model can effectively reveal the reflection characteristics of the inner surfaces of holes, and the calculation results of the model are in good agreement with the measurement results. The average fitting error of the two materials is 6.22%, which can accurately describe the reflection characteristics of hole inner surfaces and can be applied to the detection and morphological reconstruction of inner surface defects.

Measurement of gas volume fraction using non-dispersive infrared technology cannot avoid the effect caused by fast jitter, burr, vibration, etc., which affect the accuracy of measurement. In this paper, a dynamic jitter reduction inversion method based on non-dispersive infrared was proposed. Through the judgment of tilt, the reset signal was extracted, and then baseline fitting and correction were performed to reduce the baseline drift. Subsequently, by automatic iterative fitting, the integral area was obtained to realize the volume fraction inversion, so as to overcome the jitter problem of the signal. And the on-board experiments were conducted in the experimental system. Experimental results show that the maximum fluctuation value amplitude of proposed method is 58.84% and the maximum fluctuation value amplitude of the differential detection method is 62.12% when the vehicle speed varies, and the correlation coefficient of two methods is 95.263, which can effectively reduce the signal jitter problem. When the vehicle speed is constant, the average value of gas volume fraction is 10.01% for the proposed method and 9.98% for the differential detection method, and the standard deviation is 0.0374 for the proposed method and 0.191 for the differential detection method, which illustrates the accuracy of the inversion volume fraction of the proposed method and improves the stability of the measurement.

In noncontact nondestructive testing, an ancient copper mirror coated with rust cannot present complete disease information in X-ray imaging because of the different thicknesses between the edge and center of the mirror. However, to satisfy the requirements of cultural-heritage observations, X-ray images are fused, which contain numerous cracks, erosions, and other characteristics of various diseases. Scattered and small cracks are not only difficult to detect but are also susceptible to oversegmentation. To further improve the accuracy and image quality of the segmentation of ancient bronze mirror diseases, the root mean square error (RMSE) and peak signal-to-noise ratio (PSNR) indices of the images were improved while all cracks and erosions were segmented. The U2-Net was selected as the basic model and optimization strategies were considered to improve the quality and accuracy of the segmented images under the U-shaped nesting concept. Additionally, a spatial channel-attention mechanism was utilized to enhance disease detection and extraction. Subsequently, a UD-block module that utilizes dilated convolution was designed to improve the detection ability of scattered small cracks during network training. A two-level misalignment link mechanism was incorporated into the network structure to improve the PSNR and RMSE. In the fusion stage of saliency maps, a pyramid attention segmentation module was added such that the segmentation effect is more consistent with human visual perception. Finally, the result of experimental comparison and the analysis of current flaw-detection algorithms show that the Dice coefficient, Jaccard index, accuracy, Hansdorff dimension, RMSE, and PSNR obtained experimentally are the best, which can provide a reference for future studies pertaining to cultural-relic flaw-detection algorithms.

In this paper, a comprehensive multiphysics field model is developed to assess the thermal effects of direct-liquid-cooled side-pumped Ti∶Sapphire thin-disk lasers. The thermal analysis of the disks subjected to lateral nonideal pumping revealed that the total reflection transmission of pump light within the disks does not cause considerable temperature fluctuations. In addition, the thermal boundary layer thickness of the cooling fluid is considerably smaller than half of the fluid thickness, ensuring there is no thermal interference between adjacent disks. Furthermore, the thermal safety analysis revealed that, as the thermal power increases, the operational limits of the laser under the prescribed conditions are determined by the solid-liquid interface temperature, rather than the thermal stress on the lamellae. The Ti∶Sapphire lamellae can handle a thermal loading power of up to 4.43 kW, which is 4.92 times greater than that of Nd∶YAG under identical operational parameters. Finally, the analysis of thermal wavefront distortion revealed that, despite the cooling fluid possessing a thermal-optical coefficient tens of times higher than that of the lamellae, the thin thermal boundary layer prevents it from being the dominant factor. The wavefront distortion introduced by the thermal-optical effect of the fluid is balanced by the thermal-optical effect of the lamellae medium and thermal distortion. This suggests that optimizing the design can considerably enhance beam quality.

This study presents a phase chaos synchronization method based on common signal-driven semiconductor lasers. This method minimizes the impact of cavity mode hopping on phase difference in traditional master-slave synchronization structures, thereby improving the stability of phase chaos synchronization. Under back-to-back conditions, the parameter conditions for achieving a stable phase chaos synchronization are identified. With the injection intensity of 0.15, optical-frequency detuning of -2 GHz, and laser linewidth of 2.5 MHz, a phase chaos synchronization with a standard deviation of 0.015π can be achieved. Further analysis is conducted on the impact of long-distance fiber optic transmission on the stability of phase chaos synchronization. A stable phase chaos synchronization with a standard deviation of 0.04π is obtained under 160 km fiber optic transmission.

Integrated chaotic lasers play a crucial role in high-speed chaotic secure communication, key generation, and distribution. However, the existing chaotic bandwidth of integrated chaotic lasers fails to meet the requirements of high-speed applications. Therefore, this study focuses on the development of integrated broadband chaotic semiconductor lasers. Based on a short-cavity distributed feedback semiconductor laser chip developed by the team in the early stage, the conditions for achieving strong light feedback in the integrated spatial light feedback structure are analyzed and the feedback cavity length is optimized. As a result, a short-cavity distributed feedback semiconductor laser with fiber/spatial dual output light is prepared. Subsequently, this laser is integrated with a reflector and adjustment device, resulting in the development of a compact 16 cm×8 cm×7 cm integrated broadband chaotic semiconductor laser with a chaotic bandwidth exceeding 30 GHz.

The stochastic parallel gradient descent (SPGD) algorithm is one of the most efficient methods for enabling the precise phase control of laser coherent synthesis systems. However, the control bandwidth of the SPGD algorithm rapidly decreases with an increase in the number of laser paths involved in the synthesis. To meet the high bandwidth requirements of the phase control in large-scale laser coherent synthesis systems, this study proposes an SPGD optimization algorithm based on the adaptive random disturbance voltage,that is, Piecewise SPGD algorithm. The proposed algorithm uses a variable random disturbance voltage to segment the gain coefficient. The experimental simulations of coherent synthesis systems with different laser paths are conducted using the proposed algorithm. The results show that in experiments with seven laser paths, the convergence speed and stability of the optimized algorithm are improved by 36.4% and 70.6% compared with those of the traditional SPGD algorithm, respectively, and the performance is significantly improved. The proposed Piecewise SPGD algorithm can be extended to other laser coherent synthesis systems without parameter adjustment for strong universality and good performance of the phase control.

A method for collinear nanosecond double-pulse lasers with an adjustable pulse delay and energy ratio is proposed. Lamp-pumped collinear nanosecond double-pulse Nd∶YAG lasers were built for verification. The performances of single-pulse mode and double-pulse mode laser outputs were compared, and the influence of voltage applied to the electro-optical crystal on the pulse energy and time waveform was studied. The time interval between the two pulsed lasers can be controlled from 100 ns to 10 μs, hence satisfying the requirements of the majority of double-pulse lasers. Double-pulse lasers share a resonant cavity and therefore exhibit inherent coaxiality, which is ideal for obtaining collinear double-pulse lasers and can be extrapolated to other lasers.

Direct liquid-cooled end-pumped thin-disk lasers, which offer high output potential for beam quality, were analyzed focusing on addressing thermally induced wavefront distortion issues. A hydrodynamic laminar flow model was utilized for this purpose. Comparing the temperature distributions and wavefront distortions under two thermal loading conditions ideal full aperture pumping and less-than-ideal nonfull aperture pumping-revealed that heat accumulation within the coolant along the flow direction causes wavefront distortion along the same direction. In additional, a sharp decrease in temperature at the pumping edge position along the transverse direction of the thin-disk leads to considerable deterioration in the laser wavefront. Experimental results corroborate these findings. Furthermore, our thermal safety assessment highlights that the maximum thermal load of a single thin-disk is constrained by thin-disk stress, which becomes the bottleneck before the temperature rise at the solid-liquid interface. The analysis of thermally induced wavefront distortion revealed that the thermal deformation of the Nd∶YLF thin-disk has a minimal effect on wavefront distortion and the primary source of wavefront distortion is the fluid thermo-optic effect.

The study explores the dynamic response behavior of distributed feedback terahertz quantum cascade lasers under varying self-injection intensities of the optical field, utilizing the Lang-Kobayashi equation alongside a newly introduced modified end face reflection coefficient. This coefficient describes the coupling effect of distributed feedback gratings on the intracavity optical field. With increasing intensity of the self-injected light field, the laser transits from a steady state to a periodic, quasiperiodic, or chaotic state. Notably, compared to the conventional semiconductor lasers, terahertz quantum cascade lasers exhibit stability under larger self-injected intensities. Upon manipulating the target reflector, the output signal from a distributed feedback terahertz quantum cascade laser, operating in steady, periodic, and quasiperiodic states, can accurately describe the movement law of the reflector. However, in a chaotic state, the laser's output signal appears distorted. Comparing with the typical steady-state solution models reveal that the proposed theoretical model furnishes more accurate output signal patterns. This study provides theoretical support for articulating the dynamic behavior of quantum cascade lasers with grating structures, and explores the potential of distributed feedback terahertz quantum cascade lasers in the application of self-injection imaging technology.

To solve the problems of low energy coupling efficiency and poor process stability in laser welding of red copper, we use the method of adding auxiliary magnetic field to increase the absorption of laser energy by the welding base metal, and establish a numerical simulation model of magnetic field assisted laser welding of T2 red copper. The temperature field and velocity field of molten pool with and without magnetic field are compared and analyzed to explore the influence of magnetic field addition on the temperature distribution and fluid flow evolution of laser welding molten pool of red copper. The results show that with the addition of the magnetic field, the maximum temperature of the molten pool increases from 4476 K to 4868 K, an increase of about 8.7%. The average flow velocity of the molten pool decreases, and the maximum flow velocity decreases by about 21.97%. When the simulation time at 280 ms, the width and depth of the welding pool without additional magnetic field are 2.12 mm and 1.29 mm, respectively, and the width and depth of the welding pool with 120 mT intensity magnetic field are 2.26 mm and 1.34 mm, respectively. Finally, the simulated fusion line morphology is compared with the experimental fusion line morphology, and they have a high degree of fit, which verifies the accuracy of the established numerical simulation model.

A single-layer laser cladding experiment is conducted on stainless steel surfaces using the side-axis wire feeding technique. The effects of scanning speed, wire feeding speed, and laser power on the formation quality of the single-layer cladding are investigated. Moreover, a high-speed camera is used to capture the dynamic evolution of the weld pool during the laser cladding process, enabling the analysis of the relationship between process parameters and the formation of high-quality cladding. The results show that the mode of the weld wire transited into the weld pool mainly depends on the scanning speed and wire feeding speed, and it can be classified into droplet transition and liquid bridge transition. The liquid bridge transition leads to a superior formation of the cladding layer. The process parameters for achieving the highest quality cladding are found to be as follows: scanning speed of 18 mm/s, wire feeding speed of 300 cm/min, and laser power of 3400 W.

In order to effectively evaluate the multilevel combat capability of high energy laser to intercept and destroy air threat targets such as unmanned aerial vehicle (UAV) swarm, rocket, artillery and heat-seeking missile, including remote blinding of electro-optical equipment and rapid damage at a close range, this study is carried out to modeling the damage capability of 1 μm continuous high energy laser system. Considering the effect of atmospheric turbulence, atmospheric attenuation and vacuum diffraction on laser transmission in the calculation, five types of irradiated targets are selected to obtain the effectively damaging distance by high energy laser with various atmospheric conditions. The finally simulation results show that it can achieve a multi-level combat assignment of objective blinding within 18 km and destroying the target within 3 km with good visibility condition (≥20 km). The calculation model can provide theoretical basis for the design index of laser system, and provide reliable suggestions for the capability of laser system according to different combat scenarios and combat distances.

A photoluminescent probe for Mn2+ detection was constructed using photoluminescent carbon quantum dots (CQDs) obtained from the traditional Chinese medicinal material Magnolia officinalis as the carbon source via a one-step hydrothermal method. These CQDs exhibit excellent photoluminescence performance, including a maximum excitation wavelength of 285 nm, maximum emission wavelength of 425 nm, and a photoluminescent quantum yield of 28.4%. The Mn2+ photoluminescent probe shows exceptional selectivity, excellent anti-interference ability, and high sensitivity. Over the Mn2+ concentration range of 0.2?800 μmol/L, a linear correlation exists between (I0-I)/I and Mn2+ concentration, with a correlation coefficient of 0.9996 and a low limit of detection at 52 nmol/L. Mn2+ in real water samples was detected by adding 5, 50, and 100 μmol/L Mn2+ to the samples. The relative standard deviations were 0.9%?2.9%, and the recoveries were 98.8%?101.5%. This novel CQDs photoluminescent probe has broad application prospects in the environmental analysis of Mn2+.

A dual-band independently tunable bandpass frequency selective surface loaded with varactor diodes is designed, in which the unit structure consists of a composite metal surface loaded with varactor diodes, a Rogers RT5880 dielectric layer and an underlying cross feeder. Based on the finite difference time domain method and the equivalent circuit method, the structure of the designed model is optimized, and its electromagnetic characteristics are verified. The results show that when the equivalent capacitance of 0.2, 0.4, 0.6 pF and 0.03, 0.06, 0.08 pF is loaded at the outer ring and the inner ring respectively, the resonant center frequency drifts to the low frequency with the increase of the capacitance, and the low frequency passband and the high frequency passband can be modulated respectively. Based on the surface electric field distribution at the resonant frequency, the physical mechanism of dual-band frequency tunability is expounded in detail. The designed dual-band independently tunable bandpass frequency selective surface model has a simple bias network structure without considering additional feeders, which provides a new idea for active reconfigurable devices in the microwave band.

Based on the third-order aberration theory, the aberration of the coaxial four-mirror optical system is analyzed, and the mixed objective function including the primary aberration coefficient of weight distribution and structural constraints is constructed. The improved particle swarm optimization algorithm is used to solve it, and the initial structure with high image quality and specific layout is obtained. Through off-axis processing and the introduction of XY polynomial free-form surface to optimize the initial structure, a free-form surface off-axis four-mirror optical system with focal length of 365 mm, operating band of 0.4?0.7 μm,8?12 μm, F-number of 2, and rectangular field of view of 6°×2° is designed. The results show that the system achieves high energy concentration, the maximum mesh distortion is 2.12%,the optical transfer function exceeding 0.5@50 lp/mm across the entire field of view in the visible band, and the modulation transfer function(MTF) curves in the infrared band almost reach the diffraction limit. The optical system demonstrates excellent imaging quality, when combined with a digital micro-mirror device (DMD), satisfies the dynamic target simulation requirements of the optoelectronic tracking system.

Digital micromirror device (DMD) is the key device of laser direct writing lithography intrusments (LDI). We establish a diffraction model of DMD based on LDI in production conditions,and analyse the relationship between the distribution of diffraction spot in the fourier plane and the image contrast in the image plane. The different performance of the image contrast using the same type DMD devices is theoretically explained, which is consistent with the exposure experiments. Additionally, we modulate the distribution of diffraction spot by adjusting the angle of the incident light and the performance of the exposure result is significantly improved. The poor image contrast of DMD caused by production batch is overcomed and the unusable DMD chips can be properly used. Thus the material cost of production is reduced.

In recent years, the country has vigorously promoted distributed photovoltaic power generation, and accurate and reliable photovoltaic power prediction is essential to ensure large-scale distributed photovoltaic integration into the power grid. The current distributed photovoltaic power prediction methods have not fully considered the impact of meteorological factors, making it difficult to improve prediction accuracy. To address the above issues, a distributed photovoltaic short-term power prediction method based on adaptive classification and matching of weather change processes is proposed. First, scenario partitioning of weather processes is achieved through K-Medoids-Grey, and then the convolutional neural network is optimized using an improved multiverse algorithm to achieve short-term prediction of distributed photovoltaics. Taking a distributed photovoltaic user in Gansu province, China as an example for verification. The results show that in the test set, the prediction accuracy of the IMVO-CNN method under clustering is 9.83 percentage points higher than that under non clustering, verifying the effectiveness of the method.

A pixel circuit design for active laser and passive infrared detection is proposed. The pixel center distance is 30 μm. The direct current (DC) elimination feedback circuit is introduced to improve the laser detection sensitivity, and the pulse-width modulation technology is combined to achieve the dynamic range extension of infrared imaging. The circuit is designed and verified using a 180 nm complementary metal-oxide-semiconductor (CMOS) process. In laser detection mode, the eliminated DC reaches up to 5.3 μA, the amplitude sensitivity is 0.5 μA, and the pulse width sensitivity is 2.3 ns. In the infrared imaging mode, the dynamic range of the traditional high- and low-gain modes are 65.3 dB and 69.1 dB, respectively. Pulse width modulation technology can extend the dynamic range by 60 dB.

A chaotic adaptive weight improved snake optimization algorithm is proposed to solve the issues of slow convergence speed, low convergence accuracy, and susceptibility to local optima in the snake optimization algorithm of single model parameter extraction of photovoltaic cells. The initialization of chaos and the setting of adaptive weights will dynamically better allocate the proportion of search of food, combat, and mating in snake algorithm. By comparing theoretical and experimental voltametric data under different light intensities and temperatures, the improved algorithm is verified. Compared to snake optimization algorithm, the results show that the improved algorithm improves convergence speed by about 219.7%, accuracy by about 58.40%, and stability by about 49.57%. Finally, the influence of light intensity on photogenerated current is found to be greater than that of temperature, and the influence of temperature on reverse saturation current, series resistance, parallel resistance, and ideal factor is greater than that of light intensity.

Based on the un-even three-stage nonlinear interferometer instrument, this article has developed 1550 nm communication band portable polarization-entangled quantum photon source, in which three nonlinear fibers with lengths following binomial distribution (1∶2∶1) are sandwiched with two standard single mode fibers. The collection efficiency of entangled photons generated by polarized entangled quantum photon sources is greater than 85%. Under the condition of a counting rate of 4 kHz, the two-photon interference visibility of the entangled source is (77.1±0.6)%. In the case where the loss is only fiber transmission loss, the single-mode fiber is successfully used to distribute entangled photon pairs over 100 km over long distances.

The spin squeezing model has attracted a lot of attention due to its important applications in entanglement detection and measurement accuracy improvement. The transmission of quantum states in quantum informatics is a practical problem. The topic of this article is how to achieve high fidelity quantum state transfer in an open spin squeezing model. This article explores the evolution dynamics of fidelity over time in quantum state transmission based on the open spin squeezing model, and seeks effective ways to improve the fidelity of quantum state transmission. In addition to discussing the effects of spin squeezing, environmental memory, and magnetic fields on quantum state transmission, the fidelity of three different system-environment coupling models, namely the dissipative model, spin-boson model, and dephasing model, was also compared. The results indicate that the fidelity of quantum state transmission can be effectively improved by constructing a non-Markovian environment, regulating spin squeezing effects, and applying an external magnetic field. It was found that among the three different coupling models, the suppression effect on the fidelity of quantum state transmission in the dephasing model was the weakest.

Antichiral topological photonic states are a new type of waveguide states that are robust against backscattering and immune to defects. They propagate unidirectionally in the same direction along two parallel boundaries of topological photonic crystal and show broad application potential in topological lasers, integrated optical circuits, and quantum information. This review focuses on the research progress in antichiral topological photonic states, starting from the Dirac model and derivation of the classical Haldane model, antichiral Haldane model, and heterogeneous Haldane model, which demonstrate the transmission behavior of different types of topological photonic states. In addition, the implementation of chiral edge states, antichiral edge states, and one-way bulk states in photonic crystals is discussed. Next, the construction of topological optical devices based on antichiral topological photonic states, such as compact unidirectional waveguides, topological ring cavities, and topological beam splitter, are introduced. Finally, the critical issues and future development trends in research on antichiral topological photonic states are analyzed.

Vertical cavity surface emitting lasers (VCSELs) meet the data transmission requirements in parallel optical transmission, optical interconnect, and other fields, and can be applied to single channel and parallel optical interconnection networks. It is also a key optoelectronic device in broadband Ethernet and high-speed data communication. The thermal effect severely limits the bandwidth and high-speed modulation performance of VCSEL, and affects the stability of the output. By optimizing current distribution, adjusting oxidation pore size, thinning the substrate, using materials with high thermal conductivity, and bonding heat sinks, the thermal dissipation of VCSEL can be facilitated. This article reviews the research progress in thermal management of VCSEL, which is crucial for improving its high-speed modulation performance. Finally, it introduces the latest research results within the authors' research group, which are high-speed multi-hole apertures VCSEL with efficient heat dissipation structure.

Distributed sensing is widely used in various sensing fields because of its characteristics of large capacity, high spatial resolution, and long sensing distance. However, with the growing demand for high-precision sensing, it is difficult for the traditional optical time domain reflectometer to meet the demand for spatial resolution. Therefore, the optical frequency domain reflectometer with higher spatial resolution potential has attracted more and more attention, and gradually showed its advantages in multiplexing optical components. This paper reviews the research progress of optical frequency domain reflectometer, including the development of high spatial resolution and long limit sensing distance, introduces the current distributed sensing applications based on optical frequency domain reflectometer, and summarizes the composite sensing technology of optical frequency domain reflectometer, including the composite sensing technology combined with fiber grating, Fabry-Perot interferometer, and cone fiber. Finally, the prospect of optical frequency domain reflectometer technology is given.

The interaction between ultrashort intense laser pulses and solid-target plasmas can generate ultra-broadband, high-field terahertz (THz) radiation with their pulse energy ranging from tens of microjoule to over 100 mJ, spectral bandwidth covering far beyond the entire THz band, peak electric field strength reaching to tens of MV/cm, and peak magnetic field strength getting to several Tesla. The characteristics and parameters of these THz radiation depend on different laser parameters and targeting conditions, which can be attributed to different generation mechanisms. In this paper, several main mechanisms or theoretical models and their typical experiments involved on the interaction of ultrafast intense lasers pulses with solid-target plasmas for generation of high-field THz radiation are reviewed. Understanding of these mechanisms will be helpful for active modulation and optimization of these THz sources to improve the energy conversion efficiency. Due to their strong peak electric and magnetic fields, these pulsed THz sources will show many important, novel potential applications in many fields such as physics, chemistry, materials, and biomedical science.

High-resolution observations of celestial objects in astronomy using ground-based large-aperture telescopes are important for addressing fundamental scientific inquiries related to astrophysics and galaxy evolution. However, the imaging quality of ground-based optical telescopes is severely limited by disturbance arising from atmospheric turbulence. Hence, researchers are developing adaptive optical techniques to correct wave-front distortions caused by atmospheric turbulence and achieve near-diffraction-limited resolution in telescopes. One of the fundamental technologies within this area is sodium-beacon technology, which involves exciting sodium atoms at an altitude of 90 km to provide a reference for wavefront sensing in adaptive optics. In this paper, the development history of sodium beacons in China and other countries is first provided, followed by an introduction of new adaptive optical systems adopting sodium beacons. Additionally, the limitations of sodium beacons and the corresponding research issues are presented. Finally, this paper introduces new application areas of sodium beacons. Notably, sodium beacons are not only beneficial to astronomy but also to many related fields, thus indicating their broad potential in diverse applications.

Melanin index is an indicator of the melanin content in the skin. It is important to have an accurate and stable measurement of the melanin index. We utilize a non-contact measurement device to measure diffuse reflectance spectroscopy which combined with machine learning for human skin melanin index detection. First, a non-contact diffuse reflectance spectroscopy measurement device is built and the data is collected. The data is deformed using competitive adaptive reweighted sampling (CARS) and melanin index definitions respectively to prove the rationality of machine learning for spectral data deformation. Then, the performance of machine learning regression models commonly used in predicting melanin indices is compared, and finally a suitable melanin index regression model is selected. The experimental results show that among the machine learning prediction models that combined with the non-contact skin-based diffuse reflectance spectroscopy, the K-nearest neighbor regression model can accurately obtain the melanin index values, the coefficient of determination R2 reaching above 0.995 for data validation, and the minimum mean absolute error is 1.251. After comparing the accuracy of five screening wavelength and the dimensionality reduction data obtained by CARS, it is found that the dimensionality reduction data obtained by CARS not only screens out characteristic absorption peaks of different skin chromophore, but also obtains similar prediction accuracy in the prediction models. The aim of this study is to select a suitable prediction model to improve the accuracy of the melanin detection.

In this study, spectral data from various samples of tobacco leaf diseases are collected using a handheld near-infrared spectrometer. This data is then subjected to preprocessing, which includes the application of a Savitzky-Golay (SG) filter for smoothing and the first derivative to the original spectral data. Training models are subsequently developed utilizing the random forest (RF) algorithm, and sample testing was conducted. For the purposes of comparative analysis, traditional classification algorithms, such as the support vector machine (SVM), back propagation (BP) neural network, and partial least squares discriminant analysis (PLS-DA), are also employed and their performances are evaluated. It is shown by the experimental results that the classification accuracy, sensitivity, and specificity associated with the RF algorithm are higher than those associated with the SVM, BP neural network, and PLS-DA algorithms. Additionally, the F1-score and area under the curve (AUC) values obtained from the RF algorithm surpassed those obtained from the other algorithms. These results indicate that the prediction accuracy of the RF algorithm is superior, and the overall performance of the model utilizing this algorithm is the best among those tested. A rapid detection method based on a handheld near-infrared spectroscopy spectrometer and the proposed RF algorithm has been demonstrated to identify tobacco leaf diseases efficiently, non-destructively, rapidly, and accurately. This method provides a new technical reference for the detection and identification of tobacco leaf disease species.

Conventional gemological and spectroscopic analyses are conducted to reveal the gemological and mineralogical affiliation of the speciality of Xiuyan jade, Jiacui. The conventional gemological analysis revealed that Jiacui is a light green and white mottled nephrite with a waxy or oily luster, opaque to slightly transparent. The refractive index of 1.56 and the density in the range of 2.53 to 2.67 g/cm3 are measured. Microscopic observation, infrared spectroscopy, and Raman spectroscopy revealed that the Jiacui is composed primarily of antigorite, with secondary minerals such as tremolite, calcite, and dolomite, of which tremolite is relatively common. Raman spectroscopy combined with electron microprobe analysis shows that the green part of the Jiacui is usually antigorite, while the white spots are either tremolite or carbonate minerals such as dolomite and calcite. Considering that carbonate minerals are not suitable to participate in jade nomenclature as long as they are attached in the form of peridotite, it is suggested to limit Jiacui jade to a kind of serpentinized jade containing tremolite.

Fingerprints are one of the common trace physical evidence at crime scenes. To improve the efficiency of on-site investigation, the extraction methods for potential fingerprint display are enhanced, and the impact of surface free energy on the aggregation-induced emission (AIE) material for potential fingerprint extraction is explored. Twelve common types of oil and sweat latent fingerprints left on the marked objects are selected as research objects. AIE materials, combined with optical technology, are used to display fingerprints, and the display effect of fingerprints are evaluated based on surface free energy differences. The experimental results show that the AIE technology exhibits strong universality in displaying fingerprints. Cationic AIE molecules and anionic biological macromolecules (such as amino acids) bind specifically under electrostatic action, emitting yellow fluorescence under 470 nm of blue light. The surface free energy between the fingerprint and the object determines the adsorption ability of AIE molecules. Stronger surface energy leads to stronger adsorption effect of AIE molecules. Furthermore, the higher the fluorescence intensity, the better the display effect. However, at the same time, the properties of the imprinted object, surface color, fingerprint substances, and environmental pollution can affect the surface energy of fingerprints and the object, thereby affecting the appearance results of fingerprints.

Fingerprint marks on objects remain unchanged throughout their lifetime and have evidential value for individual recognition. However, many factors influence the extraction of on-site fingerprints, including poor object adaptability, ultraviolet optical damage, rough object surface limitations, complex post-processing of reagent display, and unclear tertiary feature display. Therefore, the display and extraction of on-site fingerprints have always been important research topics in the field of criminal technology. In this study, a potential fingerprint display method based on aggregation-induced emission (AIE) technology is proposed. AIE polymers excited by blue light and emitting yellow light were synthesized, and organic solvent microgrid atomization technology was used to obtain high-quality fingerprint images. Results show that AIE polymers exhibit high stability and can be stored easily for a long time. The secondary and tertiary detailed features of fingerprint marks can be clearly observed from the display results. There is also universality among various common nonpermeable and permeable objects on site. For some difficult objects, it has good visualization effects and exhibits highly efficient in situ fingerprint extraction ability. AIE nebulization can be used for displaying potential fingerprint marks on common or even difficult objects. It can target and locate potential fingerprints, extract contact exfoliated cells in situ, and provide technical support for fingerprint display and the discovery of contact DNA evidence during on-site investigations.