The amplitude-phase regeneration of 8-phase shift keying (8PSK) signal using a phase-sensitive parametric amplifier (PSA) in a silicon graphene oxide hybrid waveguide is investigated. A novel graphene oxide hybrid waveguide with two zero dispersion points at 1330 nm and 1550 nm and a nonlinear coefficient of up to 106 W-1·m-1 was designed by using a horizontal and vertical groove structure filled with high Kerr coefficient material graphene oxide. A two-stage amplitude-phase regeneration scheme for 8PSK signal is designed using this waveguide, where the phase regeneration stage is realized with a double-pumped degenerate PSA structure, and the amplitude regeneration stage is realized by wavelength conversion based on saturated four-wave mixing effect, which ultimately achieves the regeneration of the 8PSK signal in both phase and amplitude dimensions. The regeneration performance of the signal is evaluated using constellation diagram、the error vector magnitude and optical signal-to-noise ratio. The results show that this waveguide PSA has good amplitude-phase regeneration and noise compression capabilities, and has important application prospects in all-optical signal processing.

In response to the large amount of data processing in phase-sensitive optical time-domain reflection (Φ-OTDR) technology for disturbance localization, a positioning method combining region segmentation and edge detection is proposed. The fast coarse localization of the disturbance occurrence region is achieved by dividing the optical fiber into segments, followed by fine localization using an edge detection algorithm based on the Sobel operator within the disturbance region. A heterodyne coherent Φ-OTDR system is employed for data acquisition in the experiments to localize three types of disturbance events on a 5 km sensing fiber. The results show that the coarse positioning method based on region segmentation enhances the system's ability to locate disturbances in noise. The average processing time for each sample is only 0.046 s, which is an order of magnitude lower than that of the traditional method. In addition, the proposed combined method improves real-time localization over using edge detection algorithm alone, while maintaining localization accuracy. The localization error is less than 2.84 m, indicating potential for application in accurately locating external disturbances in real-time systems.

In order to solve the problem of spectrum fragmentation and inter-core crosstalk in space division multiplexed elastic optical networks (SDM-EON), a spectrum fragmentation and crosstalk-aware routing, core, and spectrum allocation (SFCRCSA) is proposed. In the routing stage, this algorithm comprehensively considers factors such as resource usage, crosstalk domain overlap, and spectrum fragmentation and selects candidate paths with low resource usage, low crosstalk, and fragmentation. In the core and spectrum allocation stages, the measurement factors of"crosstalk domain matching"and "crosstalk domain difference"are proposed. Based on this, a comprehensive measurement index of"crosstalk domain fragmentation"is presented to jointly consider crosstalk fragments and spectrum fragments, and the candidate spectrum block with the smallest value of crosstalk domain fragmentation is selected to establish lightpaths for arriving requests. The simulation results show that the proposed algorithm can reduce bandwidth blocking rates and improve the spectrum utilization.

To solve the problem of high pilot cost in high-speed railway millimeter-wave wireless communication channel estimation, this study proposes a channel estimation scheme for millimeter-wave communication systems assisted by a reconfigurable intelligent surface (RIS). In this scheme, a Kalman filter (KF) is used to predict the channel, and the estimated channel state information (CSI) is obtained based on the correlation between adjacent time slots of the high-speed railway millimeter-wave channel. Then, an orthogonal matching pursuit (OMP) algorithm is used to recover the high-speed railway millimeter-wave sparse channel to obtain the optimal reflection matrix of the RIS. Finally, in the data transmission stage, the amplitude and phase of the RIS are adjusted according to the optimal reflection matrix to control the wireless transmission environment, thereby improving the transmission performance of the high-speed railway millimeter-wave wireless communication channel. Simulation results show that, compared with the traditional least squares (LS), minimum mean square error (MMSE), and OMP algorithms, the KF-OMP algorithm exhibits superior performance in time-varying channels.

Given the need for flexibility and sensitivity of civil engineering inclination sensors, a dual-core belt inclination optic fiber based on ultra-weak fiber Bragg grating is proposed. Based on the deformation inversion theory of tangent angle recursion algorithm, a flexible inclination model of central wavelength offset is established with respect to optical cable inclination angle. Furthermore, the influence of optical cable structure on the sensitivity of the sensor is analyzed via software simulation. Based on the simulation results, the dual-core belt inclination optic fiber optical cable is prepared and tested. The results show that the inclination accuracy of the optical cable is 182 pm/(°), the maximum relative error of the measured inclination angle is 8.28%, strain transfer efficiency is 88%, and temperature compensation error is less than 4%. The dual-core belt inclinometer optical cable structure overcomes the damage caused by material shrinkage on the optical fiber during thermal processing, reduces the influence of on-site ambient temperature, and exhibits high inclination accuracy. It has a broad application prospect in the field of large scale and high sensitivity flexible survey.

In the traditional Raman-distributed optical-fiber temperature measurement system, the spatial resolution, temperature accuracy, sensing distance, and signal-to-noise ratio of the system are restricted by the sampling rate, signal quantization bits, onboard memory, and data processing ability of the data acquisition and processing module, preventing the system from performing at its full capacity. This paper presented the design of a data acquisition and processing module for long-distance Raman-distributed optical-fiber temperature measurement system based on field programmable gate array (FPGA). The module used the technique of AXI4 bus time-sharing burst read and write DDR3 memory to achieve the real-time cumulative and average processing of ultra-long data. Furthermore, the module realized data transmission between the FPGA and host computer utilizing the user datagram protocol (UDP) communication protocol and used the upper computer to demodulate and display the received data. Experimental results show that the proposed data acquisition and processing module can be applied in the optical-fiber signal acquisition range of 89.6 km, with the signal-to-noise ratio reaching 43.65 dB. Moreover, the temperature measurement accuracy is stable at ±0.21 ℃ under the 100000 times cumulative average processing of the temperature measurement signal. Thus, the data acquisition and processing module can further promote the application and development of Raman-distributed optical-fiber temperature measurement system.

Under current embedded fiber optic packaging technology, when a mechanical structure is subjected to alternating loads such as temperature or force over a long period, the different thermal expansion coefficients between the fiber optic and metal can lead to loosening and sliding of the connection surface. To solve this problem, this study proposes a double quartz tube symmetrical stepped fiber structure based on the principle of mechanical connection. This structural design enables a more reliable connection between the stepped fiber optic and metal. Based on the theory of thermoelasticity, a theoretical analysis was conducted on stepped optical fibers, and a reasonable preparation process for stepped optical fibers was proposed. The controlled variable method was used to analyze experimentally the various process parameters to improve their tensile strength. A metallized stepped fiber Bragg grating (FBG) was successfully prepared, and the effectiveness of the stepped structure was verified through experimental comparison. Experimental results show that the tensile strength of the double quartz tube symmetrical stepped optical fiber is improved by processing technology and can reach 750 MPa, which is 9.25% higher than that of the bare optical fiber obtained by mechanical removal of the coating layer (686.5 MPa). The temperature sensitivity of the prepared metallized stepped FBG reaches 15.59 pm/°C at a temperature resolution of 0.064 °C/pm. The results show that metallized stepped FBG exhibits a more stable temperature sensing performance than the metallized FBG without reducing temperature sensitivity.

In the single mode fiber coupling system of space laser communication, the parameters of the traditional laser nutation algorithm are fixed, which leads to the problem that the system convergence speed and convergence stability cannot be achieved at the same time. Therefore, a parameter self-adjusting nutation fiber coupling algorithm based on fuzzy control is proposed. The proposed algorithm uses a fast steering mirror (FSM) as the execution unit. According to real-time coupling energy feedback, the algorithm parameters are self-adjusted during the process of laser nutation convergence to improve the convergence speed and steady-state accuracy of the system. The simulation results show that the coupling efficiency, coupling precision and coupling speed of the parameter self-adjusting nutation coupling algorithm are better than those of the traditional laser nutation algorithm under the condition of no disturbance. Under the condition of disturbance, the traditional laser nutation algorithm only has a good suppression effect on the disturbance under certain conditions. However, the parameters of the self-adjusting nutation coupling algorithm have a good suppression effect on disturbances of 1?20 Hz, and the proposed method displays obvious advantages in terms of coupling efficiency and coupling stability. Hence, the proposed method is more suitable for application in laser communication links.

Considering the complex and changeable intrusion events surrounding optical fiber perimeter and noise interference, denoising of signals collected by optical fiber perimeter systems is required. First, we propose the pelican optimization algorithm variational mode decomposition to reduce noise, and the multiscale permutation entropy decision mechanism to improve the ability to suppress modal aliasing and false components. Finally, screened signals are composed of reconstructed signals to realize the entire signal denoising. The experimental results demonstrate that signal denoising of the double Mach-Zehnder optical fiber perimeter sensing system was improved during the intrusion detection process. The denoising signal-to-noise ratio (SNR), correlation coefficient, and the mean square error of the signal after noise reduction were considered evaluation indices with regard to noise reduction performance. Compared with the existing methods of ensemble empirical mode decomposition-correlation coefficient and complementary ensemble empirical mode decomposition-correlation coefficient, the SNR of the proposed method is reduced, the correlation coefficient is clearly improved, and the root mean square error of the denoising signal is slightly reduced.

For the phase demodulation of interferometric fiber optic sensors, an improved phase generated carrier (PGC) algorithm based on the linear interpolation of sampled data points was proposed to improve the dynamic range upper limit of PGC algorithms. Under a specific carrier modulation depth and initial phase conditions, data collection was performed at a frequency that was six times the carrier frequency. Through the linear interpolation of six sampling points within a single carrier cycle, six sets of orthogonal terms regarding the test signal were obtained. Phase demodulation was completed through differential cross multiplication or arctangent. Furthermore, the proposed algorithm does not require carrier mixing and low-pass filtering, thereby reducing the complexity of the algorithm. Theoretical calculation suggests that the dynamic range upper limit of the PGC algorithm can be increased by 1.58 dB. Experiment shows that when the sampling and signal frequencies are 500 kHz and 2 kHz, respectively, the peak output of the demodulation algorithm reaches 27.32 rad, upper limit of the dynamic range increases to 14.36 dB, and demodulation correlation becomes as high as 99.98%.

A refractive index sensor based on tapered four-core fiber is proposed in this paper. With the aid of a hydrogen-oxygen flame, the four-core fiber was progressively tapered between two segments of a multimode fiber. By simulating the light field of the sensing part, we prove that the tapered four-core fiber will produce stronger interference effect. Experimental results show that the sensor has a maximum refractive index sensitivity of 298.307 nm/RIU and a linearity of 99.806%. The sensor is also insensitive to temperature, which effectively avoids the cross-sensitivity effect between temperature and refractive index. With its small size and high sensitivity, the sensor is expected to have potential applications in biological and chemical sensing.

Aiming at the urgent needs of electronic information system for large broadband, parallel processing, flexible control, etc, this paper proposed a generation method of broadband optical frequency comb (OFC) with multi-combs, high flatness, and easy-tuning. By cascading a dual-parallel Mach-Zehnder modulator (DPMZM) and a dual-driven Mach-Zehnder modulator (DDMZM), and simply adjusting the direct current bias voltage and amplitude of radio frequency (RF) driven signal of two modulators, a frequency equally spaced OFC with 35 comb lines, flatness of 0.5 dB, and spurious signal rejection ratio of 15 dB is realized. In addition, the OFC generated by this scheme is easily tuned. By changing the frequency of RF driven signal, OFCs with different frequency intervals can be realized, and exhibite good stability.

To measure the defects on the inner and outer surfaces of a capsule, a null micro-interference capsule surface-defect measurement system based on white-light scanning interferometry is proposed. White-light interference technology is combined with Linnik micro-interference technology and an optical path-matching module is introduced to measure the different surfaces of different diameter capsules. Based on the concept of spherical null interference, a spherical surface is introduced as a reference surface to expand the measurement field-of-view. In actual measurements, piezoelectric ceramics are used to scan a capsule surface vertically, thus achieving a full-field white-light interference image. Phase-shifting and bat-wing correction algorithms are used to restore the morphology of the capsule surface. The proposed measurement method is built to measure the standard step plate, and the measured values are consistent with the nominal values, thus verifying the effectiveness of the measurement method. Subsequently, a capsule is measured. The results show that the proposed measurement method can accurately measure the distribution of defects on the inner and outer surfaces of the capsule.

To achieve accurate measurement of the surface shape of a cylindrical lens, research has been conducted on the measurement errors caused by reflectance. The working principle of the spectral confocal displacement sensing system is first introduced, and the spectral response of the system is derived in the spatial coordinate system using the structural parameters of the cylindrical lens. Then, theoretical research and simulation analysis are conducted on the spectral peak drift caused by the reflectance at each point and the resulting measurement errors in the surface shape. To correct the influence of lens surface reflectance on the measurement results, an error correction algorithm is proposed using S-G filtering and Gaussian fitting to achieve filtering and extraction of the peak wavelength of the spectral signal. Finally, by building an experimental platform, the measurement of the cylindrical lens surface shape based on reflectance correction is completed. The experimental results show that the mean absolute error and root mean square error of the measurement results before correction are 9.18 μm and 9.79 μm, respectively. After correction, the mean absolute error and root mean square error of the surface shape are 0.71 μm and 0.75 μm, respectively, which improves the measurement accuracy of the surface shape and validates the correctness of the theoretical analysis and the effectiveness of the proposed reflectance correction algorithm.

Microregion stress is a prevalent issue in printed-circuit board welding, transparent conductive-film plating, and micro-optical system assembly and will reduce the performance and operation safety of devices. Existing stress measurement systems are suitable for large-scale optical materials but cannot be used for microregion stress measurements. To solve the problem of noncontact and nondestructive measurement of microregion stress, a microregion stress measurement scheme based on microscopic technology was proposed. The proposed scheme integrated an optical stress measurement system based on polarization with a micro-imaging microscopic system, which could realize stress measurement at the transverse scale of millimeter or submillimeter. Taking the 2.3% relative error measurement accuracy requirement of the national standard GB/T 7962.5—2010 as an example, the system design and component error analysis of the measuring device were performed. To validate the theoretical design and measurement scheme, a set of devices was constructed for measuring stress distribution in the microregion. The device operated at a working wavelength of 532 nm with a microscopic objective power of 50× and a corresponding theoretical spatial resolution of 0.59 μm. A zero-order 1/4 wave plate working at 532 nm with a phase delay value assigned by the measuring department was the measuring object. The diameter of the measuring area was 0.96 mm, and the phase delay was 1.595 rad. Comparison with the testing result of the China Institute of Metrology 1.604 rad,the absolute error is 0.009 rad, and the relative error is only 0.6%, thereby verifying the measuring accuracy of the measuring device. Using this device, the phase distribution of quartz glass was measured in different measurement areas under different prepressures. The results show that the measurement error of this method is within 1% and there are small regional stresses that cannot be resolved by the measuring system.

Because the optical components in the high energy laser system can be evaluated by measuring the transmittance, such as the detection distance, damage ability and energy loss degree of the system, we used the common optical-path composite displacement synchronous-scanning technique via point-by-point scanning to determine the transmittance rate of large-diameter components. The upper and lower mechanical scanning structures are controlled to achieve fast scanning of the full aperture by composite displacement scanning in the circumferential and radial directions, combined with the calibration of the optical path using a galvanometer. The experimental results show that the measurement accuracy of optical element transmittance measured by the proposed method is 0.2%, the measurement aperture reaches up to 600 mm, and the measurement speed exceeds 500 h-1. These values satisfy the technical specification requirements and achieves high-precision measurements of transmittance of large-diameter laser components.

To improve the accuracy of absolute grating ruler positioning and decoding, a positioning and decoding method based on end-to-end deep learning framework is proposed. Attention modules were integrated to improve the positioning of symbol edges of UNet++, and a channel edge information extraction network was designed to achieve regression prediction of channel images to position information. To reduce cumulative errors, a loss function was designed based on the characteristics of absolute grating ruler images, which integrates the symbol edge-positioning network and the code channel edge information extraction network into an end-to-end network framework, thereby constructing a code channel-positioning module. A pseudo-random code decoding method was designed based on the center pixel of the code path to achieve absolute grating size path decoding. The experimental results demonstrate that the proposed positioning decoding method can improve the measurement accuracy of absolute grating rulers, within a 95% confidence interval (-0.206, 0.243) μm, the root mean square error is 0.265 μm, superior to existing absolute grating ruler positioning and decoding methods.

A five-axis white-light interference-measurement system is constructed by integrating a self-developed coherence scanning interferometric probe into a Moore five-axis motion platform for the surface-morphology measurement of curved optical components. To achieve automated measurement, the kinematic model of the system is investigated and the inverse kinematic equations are solved. A calibration method using high-precision aspherical calibration components with known expressions is proposed for unknown parameters in the inverse kinematics equations. Finally, an experiment to verify the calibration accuracy of the proposed system is conducted, and the results show that after automatic focusing and leveling, the error between the actual and theoretical focal coordinates remains less than ±3 μm. The measurement requirements of the probe is satisfied, and the proposed system can automatically measure the surface morphology of curved optical components.

This study proposes a method for simultaneous measurement of six-degree-of-freedom errors in precision rotating axes using absolute measurement. The proposed method addresses the limitations of current precision rotating shaft motion accuracy detection technologies, which are unable to balance high precision, efficiency, dynamic continuity, and comprehensive error measurement. Utilizing multi-wavelength phase-shifting interferometry, the method measures the instantaneous absolute pose of micro/nanostructure characteristic samples aligned with the rotational axis motion. It establishes a six-degree-of-freedom motion error model for precision rotating axes and identifies the mapping relationship between each degree of freedom error and the pose transformation of the standard micro/nanostructure feature space. By analyzing the characteristic spatial pose of micro and nanostructures, the six-degree-of-freedom error of the precision rotation axis is separated, enabling simultaneous, continuous, and high-precision measurements. Experiments conducted on a precision air bearing rotary table revealed an angle positioning error of 2.98", a tilt error of 0.91", a radial error of 399 nm, and an axial error of 37 nm.

The lattice structure of invar-alloy offers the advantages of low thermal expansion coefficient and low density, thus rendering it extremely suitable for the aerospace industry. Selective laser melting (SLM), also known as laser powder bed fusion (L-PBF), is the most widely used metal additive-manufacturing technology and offers significant advantages in manufacturing complex lattice structures. However, our current understanding regarding factors that affect the performance of invar-alloy lattice structures fabricated via SLM is inadequate. Hence, a three-factor, three-level orthogonal experimental design was employed to optimize the SLM process parameters of invar-alloy. Using tensile strength and yield strength as indicators, we propose the following optimal parameters: laser power, 280 W; scanning speed, 1000 mm/s; and scanning spacing, 0.12 mm. Tensile samples prepared under these parameters indicate yield and tensile strengths of 340 MPa and 419 MPa, respectively. Based on the optimized parameters, we investigated the effect of scanning speed on the geometric and mechanical properties of the invar-alloy lattice structure fabricated via SLM. The result shows that the lattice structure fabricated under a laser power of 280 W, a scanning speed of 1000 mm/s, and a scanning spacing of 0.12 mm exhibits both favorable mechanical and geometric performances.

This paper uses COMSOL finite element simulation software to numerically simulate the fusion forming process of the area laser exposure of a powder bed. The temperature field and flow field distribution law for this fusion formation process are obtained, and the surface tension and Marangoni effect are analyzed through the development of the flow and temperature fields. The effect of the force on the formation of the molten pool is investigated. The results show that compared with traditional laser powder bed fusion forming, area laser exposure powder bed fusion forming has a smaller peak flow rate and very small temperature gradient in the horizontal direction. The surface tension is the key factor in the formation of the molten pool and the main driving force for forming, while the resulting molten pool has less surface roughness.

A triangular core silicon photonic crystal fiber with double zero-dispersion points is used as the nonlinear working medium of a mid-infrared supercontinuum laser. The pumped optical fiber, with a peak power of 1500 W, pulse width of 100 fs, and wavelength range of 2.6?2.9 μm, is used to excite photonic crystal fiber with length of 0.1 m. A mid-infrared supercontinuum covering the 2?7 μm wavelength range is obtained. The spectral peak gain compensation is realized by varying the pump wavelength, and the spectral coverage of the characteristic wavelength of the detected gas is expanded. This mid-infrared supercontinuum with spectral peak gain compensation can be used to detect various greenhouse, toxic, and flammable and explosive gases in real time.

Silicon steel sheets are widely used in the production of motor stator cores due to their good magnetic properties. The molten pool is an important physical phenomenon in the welding process, and its dynamic behavior affects the welding quality. This paper studies the welding molten pool, and studies the influence of welding parameters on the molten pool and the temperature field changes of the molten pool through a combination of visual monitoring of the welding process and numerical simulation. At the same time, the U-Net network model has been improved, which improves network performance while achieving network lightweighting, and can accurately segment the melt pool and extract features. The average intersection ratio and average pixel accuracy reached 95.91% and 98.59% respectively, both of which were better than the original model. Numerical simulation results show that the molten pool area and welding depth are positively correlated with the molten pool temperature, and monitoring the molten pool area can better reflect the changes in welding depth. This facilitates online monitoring of the welding process and prediction of welding depth.

A fiber laser with low cavity loss, low self-starting power, stability, and dispersion-balanced performance is required for subsequent amplification, self-compression, and external field experimental applications. Therefore, this study conducts an in-depth investigation of the critical role of the phase shifter in laser self-starting using theoretical analysis and numerical simulation methods. Additionally, the relationship between the gain fiber doping concentration and the laser starting threshold is established. Based on theoretical results, a low-loss and near-zero dispersion fiber-laser oscillator was constructed using a nonlinear amplified loop mirror. The proposed oscillator achieves an ultra-low self-starting power of 60 mW and a minimum stable operating power consumption of 30 mW, thus, validating the theoretical results. To adapt to more experimental environments, a nonlinear amplification loop mirror with a separated device structure containing a variable wave plate was constructed to ensure the self-starting capability of the laser. Additionally, a piezoelectric ceramic and an optical modulator were added for laser stabilization according to the international time and frequency standard. The laser self-starting power is 160 mW with only 16 mW maintenance power required.

Fe-Cr-B-Si amorphous alloy powder was successfully prepared on the surface of low-carbon steel with excellent tribological properties by high-speed laser cladding. The effects of laser power on the microstructure, hardness, and wear resistance of the amorphous alloy coating were studied. The results show that the content and distribution of the amorphous phase in the coating are related to the laser power, which affects the dilution and actual cooling rates under a change in heat input. With an increase in laser power, the growth law of microstructure in the coating changes, and the distribution position of amorphous phase switches from the bottom to the top. When the laser power is 2200 W, the microstructure of the coating is mainly composed of an amorphous phase and unformed grain nucleation. The amorphous phase content is approximately 76% and is evenly distributed throughout the coating. The content and distribution of the amorphous phase are the critical factors that affect the hardness and wear resistance of the coating, and the hardness of the amorphous region is approximately 200 HV higher than that of the crystal region. When the amorphous phase is distributed on the top of the coating, the surface hardness and wear resistance of the coating are significantly improved.

In response to the demand for suppressing laser intensity noise in the millihertz frequency band in space gravitational wave detection, based on a low-noise chip and combined with a high stability voltage reference source, this paper designs relevant peripheral circuits to carry out the overall design and development of a semiconductor laser pump driver in a spaceborne laser amplifier. The performance of the pump driver is evaluated from both the time and frequency domains. Experimental results show that when the self-developed pump driver outputs 3.5 A, the current time-domain jitter is ≤180 μA within 4 h. In the frequency domain, by converting the current signal into a voltage signal through a sampling resistor, the voltage noise spectral density is less than 1×10-4 V/Hz1/2 at 0.1 mHz and 1×10-5 V/Hz1/2 at 1 mHz. The developed pump driver outputs laser intensity noise with a relative voltage noise spectral density below 1×10-3 Hz-1/2 at (0.1 mHz?1 Hz) in the frequency range of space gravitational wave detection. This study provides key components and experimental basis for laser intensity noise suppression in space gravitational wave detection.

In this paper, the long-pulse output characteristics of a mid-infrared solid-state laser based on different Fe2+∶ZnSe crystal samples are investigated. An Er∶YAG pulse laser with a maximum single-pulse energy of 600 mJ is utilized as the pump source, and the crystal is cooled in a vacuum chamber with liquid nitrogen. A long-pulse output with a maximum energy of 184.4 mJ and a pulse width of 1 ms, corresponding to a slope efficiency of 45.5%, is achieved on a 6 mm thickness coated sample at 85 K. For the uncoated sample, the output characteristics are compared at different fixed angles of the sample, and the results show that the output efficiency is higher when appropriately tilted.

A removal function library is a collection of removal functions with a large number of different shapes, and its establishment plays a crucial role in the invocation of removal functions during computer numerical control polishing. This study focuses on the removal functions of flexible spherical polishing heads, establishing a fitting model based on a super-Gaussian distribution. The model was applied to a least squares fitting of dozens of datasets. Multivariate interpolation methods were used for handling fitting parameters, leading to the creation of a database of removal functions corresponding to any combination of precession angle, pressure, and rotation speed. Four samples were randomly selected from the removal function library and compared with experimental data. The relative error was less than 7% in all cases, confirming the effectiveness of the method.

Based on the principle of coherent noise suppression using a ring light source, a virtual ring light source generated by a rotating optical wedge is designed for a typical Fizeau interference system. The selection of wedge angle for the optical wedge is discussed, the random noise points and coherent noise sources of the virtual ring-light-source Fizeau interference system are simulated, and the interference fringe diagrams of the point source and ring source modes are compared. The results show that the virtual ring light source can suppress the system noise efficiently while maintaining a better contrast of the interference fringes.

This study designed and analyzed a miniaturized iris recognition lens by leveraging on the natural anticounterfeiting feature of the human iris. The lens comprises four even aspheric lenses, with an f-number of 1.8, a full field-of-view angle of 42°, a total length of 2.5 mm for the optical system, and working distance is 184-389 mm. Moreover, in the range of variable working distance, for the iris recognition lens, the modulation transfer function (MTF) values at a half-cutoff frequency for each field of view all exceed 0.4, the optical distortion is lower than 0.6%, and the relative illuminance is greater than 80%. The material of the designed lens is made of optical plastic, which has advantages of small volume, lightweight, low production cost, low f-number, and good imaging quality. Therefore, the designed iris recognition lens can be applied to efficient biometric recognition in small mobile devices, such as smartphones.

This research presents a new "intermirror flexible support structure" to mitigate surface shape errors in the mirrors of airborne bathymetric laser radar (B-LiDAR) optical systems under various working conditions. The flexible structure changes the mechanical relationship between the mirrors and support structure, thereby reducing mirror deformation. In this study, an optical system was first developed using Zemax and exported to Solid works to create a 3D model of the optical system. Subsequently, Ansys was used to analyze the face shape and conduct three different types of structural stiffness tests based on the actual working conditions. The analysis results reveal that the intrinsic frequency of the support structure using a ring-shaped thin cylinder is 331.06 Hz, peak-to-valley (PV) value of mirror deformation under thermal coupling is 37.25 nm, and root mean square (RMS) value is 14.52 nm. Moreover, dynamics analysis was performed for the support structure, and the maximum acceleration response of the mirror under the applied 1g acceleration excitation is 4.32g. Under random vibration, the maximum acceleration RMS value of the mirror assembly reaches 4.7grms and maximum stress of the flexible device of the support structure is 21.3 MPa, implying good mechanical characteristics. The maximum receiving field of view verification, optical system long-distance echo reception, and onboard bathymetry experiments were designed, which can effectively complete the echo reception. The results indicate that the flexible structure of the reflector support designed in this article is stable and reliable, and can be used in airborne depth measurement lidar systems.

A regional optimization design method is proposed to reduce the astigmatism of progressive addition lenses (PAL). This method is used to optimize the near vision and astigmatic zones of PAL. First, the least squares method is used to find the spherical patch that best fits the superposed region. Subsequently, the progressive surface and spherical patch are combined proportionally to reduce the astigmatism of PAL. Finally, the Zernike polynomial regional fitting method is used to smooth the lens surface at the boundary of the superposed region, thereby reducing unnecessary astigmatism due to surface mutations. The test results of the initial design and optimized lens samples demonstrate that the maximum astigmatism of PAL after optimization decreases by 14.3%, area of maximum astigmatism decreases by 30.5%, and range with astigmatism less than 0.06 D in the near vision area increases by 30.4%. This optimization design method significantly reduces astigmatism while maintaining a relatively unchanged focal power distribution, expanding the effective visual range in near vision areas and improving visual experience for wearers.

To improve the reliability of micro-electro-mechanical system (MEMS) micromirrors during their operation, an electromagnetically driven MEMS micromirror with a mirror measuring 5 mm×6 mm and a new torsion beam structure is designed. A finite-element simulation algorithm is used to simulate the MEMS micromirror, improve the design rationality of its motion mode, and complete the process preparation and encapsulation of the designed structure. The prepared two-dimensional MEMS micromirror offers the advantages of simple process, low manufacturing cost, and high corner stability. Test results show that the MEMS micromirror equipped with the new torsion beam can achieve biaxial rotation, with a fast-axis resonant frequency of 1082.2 Hz and an optical angle of 53.9°, as well as a slow-axis operating frequency of 60.0 Hz and an optical angle of 20.8°. The results of stability test indicate that its mechanical half-angle error is 0.21° and its overall angle fluctuation is less than 2.6%. This two-dimensional MEMS micromirror has a large angle and exhibits high stability, thus satisfying the demands of MEMS lidar.

Metasurface absorbers (MA) can absorb electromagnetic (EM) wave energy, reduce signal reflection or transmission, and are crucial for protecting sensitive electronic devices from EM interference. This article proposes a pseudo-waveform-selective metasurface absorber (PWSMA) based on a square-ring resonator structure with a lumped resistor, which can simulate the waveform-selection characteristics of nonlinear MA, achieving strong absorption of continuous wave or long pulse signals and low absorption of ultrashort pulses at the same operating frequency. The designed PWSMA basic unit exhibits a surface metal square-ring resonator structure with lumped resistance and comprises an intermediate dielectric isolation layer and a bottom grounding layer. The results show that the PWSMA has an absorption rate of 98.6% for continuous waves with a frequency of 3.3 GHz, while for ultrashort pulses with a pulse width of 0.5 ns at the same frequency, the absorption rate is only 43.9%, indicating significant selective absorption performance for continuous waves. The waveform-selection response characteristics based on linear MA mainly originate from the dispersion behavior of the resonator structure rather than the full wave rectification and frequency conversion characteristics of the nonlinear circuit. The absorption rate of PWSMA significantly increases as the pulse width increases. In particular, when the pulse width exceeds 100 ns, the absorption rate of the pulse wave reaches 98.3%, which is similar to that of continuous waves across the entire frequency range. In addition, the PWSMA cannot exceed the Rozanov limit in terms of the absorption range for pulsed and continuous waves. Results indicate that changing the resistance value can significantly adjust the absorption characteristics of the PWSMA for continuous waves and pulse signals.

To address changes in the Mueller-matrix polarization characteristics of polarized light passing through hazy environments containing ellipsoidal particles, this study employs a combined method involving a T-matrix and Monte Carlo simulation to perform multiparticle scattering simulations. Using the Mueller-matrix polarization decomposition method, the effects of different shapes of ellipsoid particles as well as the differences among spherical particles on the Mueller-matrix patterns, dichroism, resulting retardance, and depolarization are analyzed. The results show that for the single scattering of ellipsoid particles, when the horizontal-to-vertical ratio of the ellipsoid particle is reciprocal, the depolarization values and polarization degrees of a pair of ellipsoidal particles are similar. For multiple scattering, a sphere and an ellipsoid can be distinguished by Mueller-matrix elements M24, M34, M42, and M43, whereas the orientation of ellipsoid particles can be distinguished by Mueller-matrix elements M12, M13, M21, and M31. The dichroism of the ellipsoid particles becomes weaker than that of the spherical particles as the horizontal-to-vertical ratio increases. The phase-delay value of the ellipsoid particles does not significantly affect the shape variation of the ellipsoid particles, although its effect is stronger than that of the spherical particles. This study provides a theoretical foundation for future investigations pertaining to the Mueller matrix of ellipsoidal particles and provides a new method for atmospheric particulate-matter detection.

Generalized measurement of qutrit states facilitates the accomplishment of complex tasks in quantum information processing. In this study, we propose a 3D quantum state measurement method by encoding qutrit states into a two-qubit system representing the walker's position and a two-dimensional coin. This is easily realized in experiments. With appropriate coin operations that vary with the walker's position and evolution time during the quantum walk, it is possible to completely distinguish non-orthogonal qutrit states based on the probability distribution of the walker's final position. This achieves a symmetric informationally complete positive operator valued measure for qutrit states. The feasibility of the proposed method was proved via simulations conducted on an IBM quantum computer, producing results that were close to the theoretically calculated probability distribution. Thus, this study establishes a foundation for the measurement of high-dimensional quantum states.

Instantaneous bandwidth is one of the fundamental technical indexes of the Rydberg atomic microwave superheterodyne receiver system that directly affects its practical application in communication, radar, and navigation. According to the laser-atom-microwave interaction mechanism, laser parameters significantly influence the instantaneous bandwidth, especially the probe laser diameter and power. This study uses an optical lens combination to control the diameter of the probe laser and a half-wavelength plate to control the probe laser power. The instantaneous bandwidth under different probe laser diameters and powers is measured and its influence law is analyzed, supporting the optimal design of the Rydberg atomic microwave superheterodyne receiver system. The experimental results show that the decrease in beam diameter and power can expand the instantaneous bandwidth, and the expansion ability is gradually enhanced; however, the response amplitude decreases with the decrease in beam diameter and power.

Owing to the increasing demand for all-solid-state LiDAR applications in autonomous driving technology, the conventional mechanical LiDAR featuring a large size, a heavy weight, and high power consumption can no longer adapt to the current application scenarios. Hence, optical phased-array technology has received attention as a new approach for realizing all-solid-state LiDAR. Optical phased array is a type of electronically controlled scanning-beam-pointing control technology. It offers non-mechanical deflection ability, a wide field-of-view, low power consumption, and lightweight excellent performance, satisfying the application requirements of all-solid-state LiDAR well. This paper first introduces the basic operating principle of optical phased arrays and reviews the recent research progress in optical phased arrays based on different materials both in China and abroad. Subsequently, the advantages and disadvantages of optical phased arrays based on different materials are compared. The key technologies required for the further development of high-performance optical phased arrays to be used in all-solid-state LiDAR are highlighted. Finally, the future development of optical phased array technology is considered and prospected.

To achieve full range and high-precision measurement of CH4 gas, a laser CH4 sensor based on tunable diode laser absorption spectroscopy (TDLAS) technology has been developed, which integrates wavelength modulation spectroscopy first harmonic normalization second harmonic (WMS-2f/1f) technology and direct absorption spectroscopy (DAS) technology. The sensor utilizes a distributed feedback laser with a central wavelength of 1653.72 nm as the detection light source, and realizes real-time inversion of CH4 volume fraction through a built-in microcontroller unit main control chip. A fusion algorithm of WMS and DAS inversion volume fraction data based on fuzzy control S-type membership function is proposed. Minimum root mean square error (RMSE) verification is performed on ten similar sensors, and the optimal fuzzy interval is determined to be in the range of 0.024‒0.038. Through comparison, this algorithm has effectively reduced the root mean square error of the system compared to the traditional full range measurement method. The test results demonstrate that the remeasurement error range of the full range test of the sensor is -5.28%‒3.67%, indicating that the sensor has high accuracy for the full range measurement. The detection limit of the sensor is evaluated at 3.04×10-5 using a 3×10-4 2f/1f measurement signal, combined with the optical path length of 0.07 m, and the minimum detectable integral volume fraction in 1 m optical path is 2.13×10-6. The 0.01 volume fraction gas is measured for a long time and the Gaussian distribution of its inversion concentration is calculated. The maximum statistical value is in the range of 0.997×10-2‒1.002×10-2, and the half width at half maximum of the Gaussian fitting curve is 1.43×10-4.

Three-dimensional (3D) inorganic micro and nanostructures play an important role in photonics, quantum information, aerospace, energy, and other fields. Inorganic microstructures prepared using traditional methods usually exhibit low resolution and uncontrollable morphology. The precise and controllable fabrication of 3D inorganic micro and nanostructures is a critical problem. Because of advantages such as 3D fabrication capability, high precision, and controllable morphology, laser fabrication can realize the preparation of 3D, high-resolution, and multiscale micro and nanostructures; furthermore, it can address the problem of accurate and controllable preparation of these 3D structures. In this study, the research progress of laser fabrication of inorganic micro and nanostructures was reviewed. First, continuous wave and ultrafast pulse laser fabrication methods were discussed, and especially, the femtosecond laser fabrication of 3D inorganic microstructures and nanostructures, including pure inorganic material systems, organic-inorganic hybrid systems, and polymer templates, were summarized. Further, the applications of 3D micro and nanostructures in optical devices, quantum chips, information storage, aerospace, and bionic structures in recent years were summarized. Finally, we highlighted the potential future development of the laser fabrication of 3D inorganic micro and nanostructures.

High-speed optical communication systems, such as the Internet, super-computing, and data center optical interconnections, and applications such as LiDAR and display, require higher performance for semiconductor lasers, such as the single mode, single polarization, high speed, and high power. This article presents a review of the research progress of surface-emitting semiconductor lasers, mainly consisting of vertical-cavity surface-emitting lasers (VCSELs) and photonic-crystal surface-emitting lasers. This includes designing surface grating, relief grating, and high-refractive-index contrast grating VCSELs to achieve the single mode and single polarization simultaneously. A zinc diffusion zone is introduced, a transverse coupling cavity is established, and a multi-hole-aperture oxide-confined VCSEL is constructed to achieve single-mode high-speed characteristics. A surface grating-loaded VCSEL for slow light is constructed, a zinc diffusion zone is introduced, and multi-junction or multi-aperture VCSELs are designed to achieve a single mode and high power. Photonic-crystal surface-emitting lasers are introduced to achieve a breakthrough performance of a single mode, high power, and minimal divergence angle. Finally, the development trends of surface-emitting lasers are discussed.

Large-aperture optical telescopes are important for the development of the future deep-space detection technology, and their performance improvement will lead to higher requirements for the measurement and suppression of optical axis jitter. In this context, this article summarizes literature on jitter measurement and suppression techniques, published domestically and internationally, covering contact and noncontact measurement methods, suppression techniques for vibration source equipment, transmission pathways, and optical loads, and system integration analysis techniques. The analysis of the current research status regarding jitter measurement and suppression reveals that current research primarily focuses on local experiments or simulations, lacking a comprehensive system solution; hence, it is proposed that integrated analysis methods combined with measurement and suppression technology will become a future research hotspot.

This review examines several typical fibre grating flow sensors. Firstly, it introduces the basic principle of fibre grating sensing, and then describes research and development of flow sensors based on FBG sensing principles at home and abroad in detail, including the temperature response and strain response of fibre gratings. Finally, it looks forward to the development trend of flow sensing technology using fibre gratings.

Fiber sensing technology has emerged as one of the most remarkable and rapidly developing technologies globally. It constitutes one of the three pillars of the information industry, alongside communication technology and computer technology, symbolizing the forefront of contemporary science and technology. Raman distributed fiber temperature sensing technology, renowned for its resistance to electromagnetic interference, electrical insulation, intrinsic safety, high sensitivity, and compact size, finds extensive use in monitoring the health and safety of national large-scale infrastructure. Moreover, it holds significant application value across various critical domains, including deep sea and deep earth, polar scientific research, large-scale water conservancy projects, and intelligent power grids. This study introduces the basic working principle of Raman distributed fiber temperature sensing technology. Addressing current scientific challenges and technical barriers in Raman distributed fiber sensing technology, this review summarizes research advancements in compensating for Raman optical attenuation discrepancies, improving signal-to-noise ratio (SNR), and ameliorating the Raman transmission equation to improve system temperature measurement accuracy. This study emphasizes the research progress of our group and discusses developmental trends in the field.

In this study, laser-induced breakdown spectroscopy (LIBS) combined with machine learning algorithms was employed to identify the grades of nine homogeneous, national, standard alloy-steel samples. The original LIBS spectra of the alloy steels were processed using a statistically sensitive nonlinear iterative peak-clipping (SNIP) algorithm for continuous background subtraction. Principal component analysis (PCA) was used to reduce the dimensionality of spectral data and eliminate redundant information. The first 10 principal components constitute 94.3% of the total variance. The LIBS spectral data of the nine homogeneous alloy steels were partitioned into a 7∶3 ratio to create training and testing datasets. Based on the first 10 principal components obtained from PCA, PCA-support vector machine (SVM), PCA-decision tree, PCA-K nearest neighbor (KNN), and PCA-linear discriminant analysis (LDA) models were established for alloy-steel identification. The average accuracies of the four models for the training set are 99.06%, 97.47%, 90.47%, and 100% for the SVM, decision tree, KNN, and LDA, respectively, whereas those for the testing set are 96.29%, 79.63%, 67.04%, and 100%, respectively. The PCA-LDA model achieves a 100% identification rate for homogeneous alloy-steel grades. This study provides method and reference for the rapid identification of homogeneous alloy-steel grades using laser-induced breakdown spectroscopy.

In order to achieve high dynamic range (HDR) displays, the backlight LEDs of monitors need to increase the drive current to improve the luminous intensity. However, LED efficiency will be decreased with the increasing of current, and a fourth primary colour (orange) was introduced to mitigate the decrease of efficiency. Energy saving was achieved by mixing four primary colours and the brightness was allocated to different groups of three primary colour LEDs to reduce the drive current. Results show that the maximum power consumption can be reduced by 23.7% at HDR brightness of 1000 cd/m2, and the average power consumption reduced by 10.97%. In addition to the brightness allocation method, this paper also investigated the effect of improving the LED"green gap"on mitigating the efficiency decline.Compared with the power consumption of this scheme, the proposed method is 5 percentage points lower in white conditions and more than 3 percentage points lower in other situations, once again verifying the superiority of the proposed method in existing methods.