A parallel simulation method for underwater wireless optical channel simulation is proposed based on open multi-processing (Open MP) and compute unified device architecture (CUDA) to address the computational complexity and low computational efficiency of the Monte Carlo-based model. The simulation calculation efficiency is improved by transplanting computationally intensive parts to threaded parallel computing. Three optimization schemes are introduced to accelerate merging by eliminating invalid photons, limiting high-scattering events, and reducing the amount of data exchange between main and video memories, further improving the simulation efficiency. The acceleration effects in various water types, computing environments, and photon numbers and distances are evaluated. The parallel calculation efficiency of graphics processing units has an acceleration effect of up to 300 times, whereas that of central processing units has an acceleration effect of 90 times compared with traditional serial simulation.

Observation data of aerosol vertical distribution, particle number concentration, mass concentration, scattering characteristics, and visibility were captured using three-wavelength polarization lidar and online aerosol-monitoring instruments during a dust episode at Shouxian National Climate Observatory from January 14 to 16, 2021. These data, combined with the conventional surface meteorological observation data, were then used for analyzing the stageful evolution characteristics of aerosol microphysics, optical properties, and vertical distribution during the dust episode. The results show that the peak value of the total number concentration of aerosol particles in the transit of dust is 5431 cm-3, the mass fraction peak value of PM10 is 447.2 μg/m3, and the mass fraction ratio between PM2.5 and PM10 is 0.43±0.10. Furthermore, the aerosol spectrum distribution in the dust, haze, and clear-sky stages could be expressed as the superposition of two fine-grained modes and one coarse-grained mode. The number concentration of aerosol particles in the dust stage is significantly higher than that in the haze and clear-sky stages, and the geometric average radius of particles in the two fine-grained modes is basically the same. In the coarse-grained mode, the geometric average radius of particles in the dust stage is 2.24 μm, which is significantly higher than 1.74 μm in the clear-sky stage and 1.79 μm in the haze stage. The average value of the total scattering coefficient in the dust stage is greater than those in the haze and clear-sky stages. In the dust stage, the backscattering ratio of the aerosol particles is found to be smaller, indicating that the air is dominated by larger dust particles. The vertical distribution trend of the aerosol-extinction coefficient at three wavelengths is found to be basically the same, and the extinction coefficient in the dust stage is greater than those in the haze and clear-sky stages. The height of the aerosol layer in the dust stage extends to 3 km near the ground, the depolarization ratio is basically greater than 0.1, and the Angstr?m index is in the range 0.1?0.4.

The Ge-based photodetector has a broad application prospect in light detection with its unique communication bandwidth response characteristics and good compatibility with CMOS technology. However, the response band of current commercial detectors is generally limited to a specific band, which is not easy to meet the detection requirements of multiband fusion and miniaturization. Therefore, in this paper, a graphenemetal-insulator-semiconductor (MIS) junction-based photodetector is fabricated by introducing a thin SiO2 interface layer between multilayer graphene and N-type Ge. The effect of SiO2 with different thicknesses and graphene layers in the MIS junction device is investigated. The influence of the number of layers on performance of the MIS junction device is also tested. The spectral response range, current-voltage curve, responsivity, on-off ratio, and other optoelectronic properties of the device are tested. The results show that the device has a response in the wavelength range of 254-2200 nm, and the responsivity and the on-off ratio peaked at 980 nm, which are 73.86 mA/W and 1.74 × 103, respectively. The rise and fall times are 1 ms and 3 ms, respectively.

One of the hottest subjects in the current optical communication sector is the use of optical phase conjugation (OPC) method to decrease fiber nonlinearity. To enhance OPC's capacity to suppress fiber nonlinearity, we propose a two-stage optimization strategy for maximizing the power of conjugated signals and the cumulative dispersion of conjugated signals for the dispersion-managed optical transmission link of erbium-doped fiber amplifiers. The theoretical analysis reveals that the performance gain brought by power optimization is only related to the dispersion-attenuation coefficient ratio of the fiber. Therefore, the theoretical analysis findings are validated using two types of dispersion management connections as examples: super-large-area fiber and inverse dispersion fiber (SLA-IDF) and standard single-mode fiber and dispersion compensation fiber (SSMF-DCF). The numerical simulation results show that after the 9-channel polarization multiplexed quadrature-phase-shift keying signal is transmitted over 1920 km (24×80 km), for the SLA-IDF link, the optimal signal-to-noise ratio (SNR) of the system after optimizing the optical intensity and dispersion is improved by 3.8 dB and 1.0 dB, respectively; for the SSMF-DCF link, the optimal SNR of the system after optimizing the optical intensity and dispersion is improved by 0.4 dB and 1.6 dB, respectively.

In the fields of equipment precision manufacturing, space navigation, positioning, and satellite formation, the accuracy of the laser interferometer measurement system is required to reach the pm level in the measurement range of thousands of meters to hundreds of kilometers, which is a requirement that cannot be achieved by traditional laser ranging technology. To solve the above issues based on the characteristics of equally spaced multispectral optical frequency combs, classic principle of multiwavelength laser interferometry, and theoretical mathematical model of the heterodyne interferometric distance measurement method of the dual-optical frequency comb, the effects of phase measurement uncertainty, air refractive index, and the uncertainty caused by signal repetition frequency on distance measurement are investigated in this paper. The results show that the uncertainty of distance measurement decreases with the increase in temperature, pressure, and carbon dioxide volume fraction. In addition, compared to the traditional optical frequency comb interferometric ranging method, the higher the temperature and pressure, the more obvious the decrease of the measurement distance uncertainty of the dual-optical frequency comb heterodyne interferometric ranging method; when the volume fraction of carbon dioxide per cubic meter is in the range of 0.75%-0.80%, the distance measurement uncertainty of the two methods tends to be consistent.

To reduce temperature measurement error caused by the wavelength-related loss of Raman scattering light and extra noise of photodetector and Rayleigh noise in scattering lights of the Raman-distributed temperature sensor system, an anti-Stokes optical noise reduction method developed by analyzing the demodulation principle of distributed optical fiber temperature-sensing system in this paper. The optical fiber is laid according to the ring structure. The average value of the base noise following the Fresnel reflection peak in each measured anti-Stokes optical signal is taken as the dynamic background noise. Two sections of the optical fiber at different temperatures are used to eliminate the Rayleigh noise after the dynamic background noise. In theory, the anti-Stokes light noise reduction demodulation method prevents the temperature measurement error introduced by the reference Stokes light and eliminates the temperature measurement error caused by background noise and Rayleigh noise. The experimental results demonstrate that the maximum temperature measurement error of the modified distributed optical fiber temperature-sensing system is decreased from 5.4 ℃ to 0.6 ℃, and the temperature measurement accuracy is significantly improved.

In order to meet the application requirements of modern radar systems for linear frequency modulation (LFM) signals with high frequency and large time bandwidth product, a frequency 16-tupling LFM signal generation scheme using a cascaded double parallel Mach-Zehnder modulator and a cyclic secondary phase modulation loop structure is proposed. After theoretical analysis and simulation, it is verified that a LFM signal with a center frequency of 160 GHz, a bandwidth of 32 GHz, and a time bandwidth product (TBWP) of 310.3 can be generated when the radio frequency drive signal frequency is 10 GHz. In order to further improve the time bandwidth product of the generated signal, on the one hand, the parabolic drive signal is stretched or phase coded in the time domain to increase the time bandwidth of the generated signal. On the other hand, the parabolic drive signal is divided into multiple segments to increase the bandwidth of the generated signal. The results show that after the above processing, LFM signals with TBWP of 1272.05, 966.04, and 15346.75 can be generated, and the results are in good agreement with the theoretical analysis.

The chaotic spread spectrum time delay estimation is a challenge posed by low peak parameterization when using existing methods. Furthermore, more potential misclassification spots and poor signal-to-noise ratio (SNR) hinders cable fault signal time delay estimation. Therefore, this study proposes a new delay estimation approach that integrate the third-order cumulative one-dimensional slicing with quadratic correlation. In chaotic time delay estimation, this method was used to the Simulink simulation model. The results obtained via the simulation show that the proposed method could obtain good estimation results at lower SNR while suppressing the interference of correlated background and non-Gaussian noise when compared with existing basic intercorrelation and quadratic correlation methods. Its operation increases the absolute value of the primary peak-to-parameter ratio by more than 1.70 dB and decreases the false peak-to-fault point peak ratio by more than 0.133 when compared with the basic intercorrelation operation. This method introduces a novel technical approach for detecting fiber optic cable faults and their cable faults using chaotic spread spectrum detection.

Using three-dimensional (3D) measurement technology with linear structured light, the total 3D morphology of a workpiece can be reconstructed with continuous multi-frame contours that are adjacent. To improve the extraction speed of the centerline, a fast extraction method of stripe center based on time-continuous frame information multiplexing is proposed in this paper, which is in view of the similarity between continuous frame images. First, the centerline coordinates of the first frame laser stripe are calculated using the adaptive gravity-center extraction algorithm using stripe segmentation. Second, based on the centerline coordinate information of the previous frame, the rough location of stripe in the current frame image can be calculated quickly. Finally, the sub-pixel calculation on the centerline of the stripe is performed. According to the image similarity of time-continuous frames, the method multiplexes the centerline coordinate information to reduce repeated calculation, which can improve the algorithm speed effectively. The experimental results show that the method can achieve the centerline calculation with a higher speed of up to 133 frame/s, which greatly improves the 3D scanning speed with linear structured light and can be applied to other 3D reconstructions of large workpieces.

This study proposes a method for Laplace surface recurrence based on optimized control point monitoring to tackle the challenges of high-intensity and time-consuming of surface deformation detection engineering processing in the assembly process. First, the model is simplified based on various constraints, control points are placed, and spacing is optimized using a qualitative analysis of the simplified model’s deflection. Second, by mapping the source model with the centroid as the reference point and determining the corresponding control point coordinates on the source model, the relationship between the source model and the real deformation component is established. On this basis, the surface is subjected to Laplace deformation to ensure that the reconstructed surface can reflect the real deformed component. The experimental results show that the reconstruction accuracy of 93% can be controlled within 0.1 mm, reflecting the actual deformation of components. This study is significant in terms of engineering guidance in practical application.

Lunar laser ranging (LLR) has promoted the development of earth-moon science, lunar spatial reference, and gravitational physics. To fully use the LLR data according to the widely used International Earth Rotation Service 2010 (IERS 2010) specification, the solid tide, ocean tide, atmospheric delay, and general relativity effects are modeled, and the LLR observation model is established in this paper. All LLR observation data provided by the International Laser Ranging Service are checked with the model, and the generated Lunar Corner Reflector Prediction File in CPF (Consolidated prediction format) supports Yunnan Observatory's independent LLR observations. The INPOP19a, DE430, and EPM2017 almanacs are input as observation models to check the LLR standard point data. The results show that the INPOP19a almanac is closest to the measured data than other almanacs.

This study proposes a method for the overall measurement of small deformations based on multi-camera three-dimensional digital image correlation (3D-DIC) to achieve flexible and high-precision measurement of deformations in multiple key regions of complex satellite structures. A binocular 3D-DIC subsystem is established for obtaining high-precision deformation fields in each key area. Combined with the beam adjustment optimization and the 3D reconstruction method of the same name point, the external calibration of the pose of the subsystem is completed. The measured data of the subsystem is spliced according to the calibration parameters, and the global deformation field is obtained. Under laboratory conditions, the overall deformation field and measurement error of multiple installation surfaces are measured in the thermal deformation experiment of the satellite honeycomb structure. The results show that the overall displacement measurement error of the method for the system is 0.96 μm±0.45 μm/m. The method meets the measurement requirements of a high-precision and flexible measurement range. Also, it has good applicability to overlapping and discrete fields of view and provides a reliable measurement method for monitoring the satellite structure’s stability in space.

A metal-insulator-metal structural filter, which comprises two oblique symmetric rectangular ring resonant cavities and a waveguide, was built using a boundary coupling approach based on surface plasmon polaritons. A finite element method was employed to simulate and examine the filter, and the magnetic field distribution map and transmission curve were generated. The findings demonstrate that the filter’s maximum transmittance in the pass-band is 0.969, and its minimum transmittance in the stop-band is close to 0. This filter also has a wide pass-band and stop-band features, and a smooth transmission curve. The filter’s transmission curve can be red-shifted or blue-shifted by adjusting the structural parameters, and by setting certain structural parameters, the function of the on-off of the second and third communication windows of the filter can be controlled selectively while keeping the first communication window passing through. Thus, the filter can be employed as a band-pass/band-stop filter, which has crucial applications in high-density integrated circuits and optical fiber communication. furthermore, an electro-optic switch function can be accomplished by enhancing the structure and adding the electro-optic material DAST.

In this paper, we propose a SiGe grating coupler to realize vertical coupling between the single-mode fiber and the SiGe on-chip device. To improve the coupling efficiency of the SiGe grating, we adopted a metal layer as the reflecting mirror on the chip backside, and we optimized the structure, including the etch depth, etch groove width, and grating period, using the finite-different time-domain method. We computed the grating coupling efficiency by analyzing the power and electric field distribution with and without the metal reflective layer. The simulation results show that the maximum coupling efficiency of the uniform grating is increased by 9.4 dB compared with the case without a metal layer, and its directionality is significantly improved. The maximum coupling efficiency of the SiGe grating obtained by simulation optimization is -1.34 dB at 1466 nm. Furthermore, we simulated and designed a two-step apodized grating based on the uniform grating, which further increased the maximum coupling efficiency by 0.55 dB compared with the uniform. Additionally, we performed a tolerance analysis on the coupled grating, including the thickness of the metal layer, the refractive index of the SiGe material, and the size of the grating. The analysis results show that the SiGe grating has a high tolerance for process deviations. Also, we fabricated a SiGe coupling grating, and the test results show that the maximum coupling efficiency of -2.7 dB is obtained at 1465 nm.

In this paper, the analytical expression of the light field distribution in the cavity and the wall of the laser indirect driven fusion target after the flat-top Gaussian beam is focused by the finite number of small amplitude modulated defects are derived. The influence of the size of the defect and the modulation amplitude on the intensity distribution is studied in detail. The influence of incident angle on the diffracted light field of the modulated beam projected onto the cavity wall is further studied. The results show that the larger the size of the defect, the larger the modulation amplitude of the defect, the more obvious the disturbance of the beam, and the longer the transmission distance required for the optical field distribution to be restored to the flat-top Gaussian distribution. When the incident angle of the incident beam is less than 10°, the path of the beam before reaching the cavity wall is long, and the spot projected by the modulated flat-top Gaussian beam on the cavity wall diffuses to the x-axis direction. The change of intensity disturbance caused by defect is obviously weakened, and the spot intensity decreases as a whole.

The fiber laser linewidth is an important index reflecting the spatial resolution of laser radar and the measurement accuracy of laser precision measurement systems, and it has important application value in engineering practice. In this paper, based on the basic theory of linewidth measurement and the optical self-injection feedback method, the linewidth of the fiber laser before and after adding the optimized structure is compared, and the optimization effect of the optical self-injection dual-cavity feedback structure on the linewidth characteristics of the fiber laser is explored through experiments. A composite ring fiber laser and a self-injection dual-cavity feedback linewidth optimization structure are built, and the linewidth of the output light is measured by the delayed self-heterodyne method. The experimental results show that the optical self-injection dual-cavity feedback structure can further compress the fiber laser's average linewidth from 1.782 kHz to 1.319 kHz, and achieve a narrower linewidth laser output.

Short-wavelength red laser is a new wavelength light source that is urgently needed to be developed for laser display and biomedical applications. In this paper, a red light semiconductor laser with a wavelength of 620 nm has been designed and simulated based on a Ge/SixGe1-x substrate. The laser uses a Ge substrate and a SixGe1-x substrate layer. By changing the Si mole fraction in the SixGe1-x layer, the lattice constant of each layer of the AlGaInP materials in the laser structure is adjusted to achieve a GaInP quantum well with a high Ga mole fraction and shorten the laser wavelength of the GaInP quantum well to 620 nm. By calculating the physical parameters of SiGe and AlGaInP materials, the influence law of GaInP quantum well active region structure and SixGe1-x substrate layer components on the output characteristics is studied, and the structural parameters of the laser are optimized. The simulation results show that the laser designed at 298 K temperature has an output wavelength of 620 nm, a threshold current of 0.58 A, an output power of 1.20 W, and a conversion efficiency of 38.3%.

In order to solve the problem of high brittleness and easy cracking of the Al2O3-ZrO2 ceramic coating prepared by laser cladding technology on the surface of titanium alloy, effectively enhance the properties of titanium alloy and expand its application range, we improved the crack sensitivity of Al2O3-ZrO2 ceramic cladding layer by adding rare earth oxide CeO2 to the cladding layer material. By analyzing the macro and microstructure of the cladding layer, testing its properties, the influence law of CeO2 content on the crack sensitivity of the cladding layer was studied, the optimal content of Al2O3-ZrO2 ceramic coating prepared using CeO2 regulation-assisted laser cladding was explored, and the action mechanism of rare earth oxide on the crack sensitivity of the cladding layer was revealed. Experimental results show that the number of cracks in the cladding layer is significantly reduced by adding rare earth oxides. When the CeO2 mass fraction is 0.8%, the cladding layer's microstructure is the densest and the fracture prevention effect is the most visible. The fracture toughness of the cladding layer is significantly improved compared with that without the addition of rare earth control assistance, from 4.1 MPa·m1/2 to 7.3 MPa·m1/2.

Laser selective melting technology was used to prepare three types of 316L stainless steel lattice structure samples with different porosities and pore sizes. The samples were subjected to quasistatic uniaxial compression tests. The test results showed that, compared with the solid metal structure, the elastic modulus of the lattice structure decreased from 180 GPa to 2 GPa. Furthermore, porosity was found to be the main factor affecting the lattice structure stiffness, and the corresponding numerical relationship was obtained. Under the condition of keeping the overall size and porosity unchanged, the change of lattice size and number was observed to have little effect on the stiffness and yield strength of lattice structure. The finite element model was applied to analyze the macroscopic deformation and stress distribution of the full-size lattice structure and the variation of the micro stress and strain of the single lattice. The printing accuracy of the sample was tested using an industrial CT system. The test show that the diameter of the rod measured perpendicular to the printing direction is greater than that measured parallel to the printing direction. According to the test results of the industrial CT system, the deformation mechanism of lattice structure is obtained.

The minimum characteristic size for 316L stainless steel was determined using a laser powder bed melting experiment of the lattice structure. Four types of lattice cell structures were designed. The relationship between different lattice cell configurations, packed density, and heat exchange efficiency was simulated by Materiallise Magics software. A lattice cell configuration with a better heat exchange efficiency was selected. Three different densities with the best lattice cell configuration were filled, and Materiallise Magics software calculated the heat exchange area of the three different densities of lattice structures. Laser powder bed melting additive manufacturing under three densities was used to fabricate a 316L stainless steel lattice structure. Computed tomography was used to reconstruct the three-dimensional image of the lattice structure, and the heat exchange area of the structure was determined. The heat exchange efficiency value was predicted using a mathematical model, and the measured value was calculated and compared. The difference between the mathematical model predicted and measured values of heat exchange efficiency of 316L stainless steel value is about 11%.

The fiber laser was used to weld the TA15 titanium alloy skin grid structure, and the coaxial high-speed camera monitoring scheme was used to collect images and extract features of the molten pool morphology under different welding parameters. The results show that the segmentation extraction method of molten pool edge based on brightness features can solve the problem of uneven brightness before and after the molten pool image, and extract accurate molten pool edge information. The molten pool width and drag angle have a strong correlation with the weld joint width, and the length, width, and drag angle of the molten pool have a strong correlation with the weld penetration. At the same time, a regression analysis model of welding process parameters and weld formation is established, and the weld forming size is predicted. The average prediction errors of the weld joint width and weld penetration are 0.14 mm and 0.10 mm, respectively.

Microstructure and mechanical properties of GH3536 alloy were examined using laser cladding deposition (LCD) forming technology on the surface of forged GH3536 alloy. The results show that an equiaxed crystal junction zone with a width of 250-320 μm is formed between the laser forming zone of the LCD forming GH3536 alloy and forged substrate. Additionally, the width of the molten pool in the forming zone is 2-2.5 mm. There is a dendritic structure and a few hole defects in the molten pool. The continuous distribution of M6C and M23C6 carbides precipitated in the bonding and forming zones during the forming process. The LCD forming GH3536 exhibits evident anisotropy since the GH3536 alloy in the forming zone has a higher room temperature tensile strength than the base material.The tensile and yield strength of the material perpendicular to the forming direction are 12.5% each higher than the material parallel to the forming direction. Although, it is 9.1% longer and its elongation is 7.7% less. Its Vickers hardness is 12.4% lower than the base material owing to the large grain size of the GH3536 alloy in the laser forming zone and few hole defects.

The alloy coating with mass fraction of 35.8%Fe-20%Ti-20%Al-24%Cr-0.2%Y2O3 was fabricated on the surface of 304 stainless steel by laser cladding process. The microstructures, elemental distributions, and mechanical properties of the coating were characterized. The results show that under the conditions of laser power of 2200 W, scanning velocity of 5 mm/s, and overlapping rate of 50%, the obtained coating has a uniform and dense structure without defects such as cracks and pores. There is a metallurgical bond between the coating and the substrate, and the dilution rate is 7.31%. Phase compositions of the coating are mainly (Fe,Cr)Al, Y2TiO7, and TiO2. The average grain size is less than 6.7 μm. As a result, the coating has high hardness and good high temperature wear resistance, the hardness reaches 550 HV (the substrate is 210 HV). The mass loss rate of wear test at 400 ℃ is only 3.67% of that of 304 stainless steel.

The spatter morphology during selective laser melting (SLM) processing varies with process parameters, and it is difficult to achieve spatter extraction under all process parameters. The spatter extraction method based on traditional threshold segmentation only supports some process parameters and has no error analysis work, and the processing results cannot reflect the real spatter state. This paper proposes a robust image processing method to extract and process them based on the spatter images of the SLM process collected by high-speed cameras.The image processing method includes five steps, in which the threshold segmentation process depends on maximum entropy threshold segmentation algorithm. The results show that the spatter image processing method can accurately extract the spatter information under multiple process parameters. When the laser power is in the range from 100 W to 150 W, the change in the spatter area and number is determined by the molten state of the powder. And the reduction of spatter area and number is caused by spatter superposition when the laser power is in the range from 150 W to 200 W.

A selective laser sintering (SLS) technique uses a method called finite element simulation to forecast and analyze temperature fields. However, the temperature field simulation computation takes a long time. An SLS sintering points temperature prediction approach, based on a genetic algorithm (GA) optimized back propagation (BP) neural network, is proposed to enhance the computation efficiency. A large number of simulation experiments of sintering point temperatures of coated sand multitrack-multilayer parts were conducted. A sintering point temperature prediction model based on GA-BP neural network was created and trained based on the above experiments. A piece of software for predicting SLS sintering point temperatures was developed. The software can quickly calculate and visually display the sintering point's temperatures based on the dimension and process parameters. The accuracy of temperature prediction was confirmed when the predicted and detected sintering point temperatures of the parts were compared experimentally.

Composition should be initially determined when analyzing temperature distribution using the refractive index measurement method. A method which divides the measured flow field by combining the phase and emission intensity distributions is proposed to confirm the composition of each region and significantly improve the temperature reconstruction accuracy. Candle-air (non-premixed flame) and propane-air (premixed flame) combustion flow fields are selected for the experiments. The refractive index, phase, and emission intensity distributions are matched. The composition distributions of both flow fields are analyzed and confirmed. A comparison of the temperature results obtained using the phase partition method (Model 1), emission intensity partition method (Model 2), and integrating phase and emission intensity partition method (Model 3) shows that Model 3 is the most reliable. Furthermore, the reliability and adaptability of the method are analyzed and discussed. This study provides a reference for the temperature diagnosis of complex flow fields based on refractive index measurements.

Based on the negative dispersion and heat dissipation characteristics of harmonic diffractive optical elements, a wide-band optical imaging system with operating band of 0.40-2.50 μm is designed in this paper. The mathematical model of the bandwidth integral average diffraction efficiency of the double-layer diffractive optical element is established. The optimum design wavelength of diffraction element is determined by Matlab software. BaF2, AL2O3, AL2O3-E and ordinary optical glass (KZFSN5, SF57) are used to design the refractive and diffractive hybrid 5-piece optical structure, and the wide-band common optical path confocal plane integration is realized by rational distribution of optical focal degree. Experimental results show that, the system has an effective focal length of 100 mm, the field angle of view is 9.4°, and the F-number is 2.8. The system achieves no thermo in the range of -40-60 ℃. At the Nyquist frequency of 50 lp/mm, the modulation transfer function (MTF) of 0.40-0.78 μm is greater than 0.6, and the MTF of 0.78-2.50 μm is greater than 0.5. Compared with the traditional wide-band optical system based on refractive lens, the system has the advantages of simple structure, small size and imaging quality close to the diffraction limit.

The linear motion dynamic target simulation system can provide an infinite distance dynamic target with linear motion relative to the aerial camera, which is used to detect the dynamic resolution index of the aerial camera. This paper completes the achromatic optical design of a collimator with a large field of view and long focal length. The dynamic target generator comprises a collimator, resolution chart, precise linear guide, and linear motor. The trajectory of the dynamic target was designed using the image motion velocity equation on an aerial camera. Based on the LabVIEW platform, the proportional-integral-derivative algorithm was used to control the linear motor to realize dynamic target simulation with an operating speed of 10-900 mm/s and instantaneous velocity error less than 1% at a constant speed segment. The result reveals that the optimized optical system's modulation transfer function is better than 0.2@100 lp/mm, and distortion is less than 0.03%.

One of the research hotspots in the field of optics is light manipulation using super surface. Herein, a U-shaped element structure is designed. The phase shift of transmitted light from 0 to 2π is realized by placing the structure in an oblique symmetrical manner and changing the geometric parameters of the structure. Using linearly polarized light, left-handed polarized light, and right-handed polarized light as incident lights, a beam deflector with polarization independent beam abnormal refraction is realized through structural optimization, and the refraction angle is 22.4°. The function of a super lens is also discussed, which provided a reference for the application of the super surface.

As an important part of quantum cryptography, quantum blind signature has attracted more and more attention in recent years. Semi-quantum protocol provides a feasible method for the practical application of quantum blind signature. In this paper, a semi-quantum blind signature protocol against collective noise is proposed by combining the semi-quantum and logical qubits resisting collective noise. In the protocol, only the signer Charlie has the complete quantum capability, which makes the demand for quantum resources of the protocol drop drastically. Through security analysis, the protocol can resist internal attack, entanglement-measurement attack and intercept-resend attack. The protocol implements reusability of keys and the scheme can be extended to quantum signature networks to realize cross-center quantum signature.

The fiber lasers operating at 1.7 μm band have important applications in many fields, such as biological imaging, gas detection, material processing, and generation of mid-infrared laser. Thus, it has received extensive attention in recent years. In this paper, the progress of 1.7 μm fiber laser is reviewed in detail, and the characteristics of different technical schemes are discussed comprehensively, including fiber gas Raman lasers based on hollow-core fibers. Combined with application requirements, the development trend of fiber lasers in the 1.7 μm band is briefly prospected.

Disease diagnosis technology based on human breath analysis, which belongs to the scope of non-destructive medical diagnosis research, is an important development direction of medical diagnosis in the future and will play an important role in non-destructive medical disease diagnosis in the future. Especially in the context of the current rampant new crown epidemic, the demand for non-invasive, real-time, and highly accurate disease diagnosis technology is more urgent. Based on the basic principles and technical characteristics of cavity-enhanced absorption spectroscopy, this paper outlines the history and current situation of the development of cavity-enhanced human breath diagnosis technology at home and abroad, and analyzes the future development direction of cavity-enhanced human breath diagnosis technology on the basis of summarizing the characteristics of human breath diagnosis, which can provide reference for the development and application of the subsequent technology.

Silicon-based photonic integration technology has made breakthroughs in several fields, but the silicon germanium material system is currently the only material that can realize all silicon-based integrated active devices and is compatible with complementary metal oxide semiconductor processes. Ge/SiGe multiple quantum wells as silicon-based optical modulators can realize short-distance optical interconnections on silicon chips, and Ge/SiGe multiple quantum well modulators based on the quantum-confined Stark effect have the advantages of low power consumption, low bias voltage, and high speed. This paper summarizes the research status and progress of Ge/SiGe-based multiple quantum well modulators. The extinction ratio, optical loss, bias voltage, electric field, modulation bandwidth, dark current, and other performance parameters of Ge/SiGe multiple quantum well modulators are discussed and compared. The development direction and challenges of Ge/SiGe multiple quantum well modulators in integrated photonics are evaluated.

With the in-depth promotion of various complex key projects in China, engineering safety has attracted more and more attention. However, deformation monitoring of rock and soil mass is one of the essential means to ensure engineering safety. Compared with traditional rock and soil deformation monitoring technologies such as electromagnetic method, acoustic emission, theodolite, level gauge, displacement gauge, and strain gauge, distributed fiber optic sensing technology has the advantages of real-time, high precision, full distribution, long-distance, and anti-interference. It has become the focus of the research and application field of rock and soil deformation monitoring. This paper summarizes the application status of fiber optic sensing technology in rock and soil deformation monitoring, the principles and application scenes of several typical distributed fiber optic sensing technologies are introduced, the critical problems of fiber optic sensing technology in rock and soil deformation monitoring are discussed, and the application achievements and challenges of fiber optic sensing technology in slope, water conservancy, tunnel, pipeline, railway, land subsidence, and collapse monitoring are analyzed. Finally, the problems and solutions of fiber optic sensing technology in rock and soil deformation monitoring have been prospected.

Laser absorption spectroscopy (LAS) technology is widely used in gas flow detection due to its advantages of high sensitivity, high precision, and non-contact measurement. In the application scenarios of combustion diagnosis, leakage detection, and localization, the demand for spatial distribution measurement has been presented. Laser absorption tomography (LAT) and laser absorption imaging (LAI) based on LAS technology can not only realize the two-/three-dimensional (2D/3D) imaging of flow field but also have good adaptability to the complex environment in practical engineering with high time resolution, which will still be the focus of research in related fields in the future. Here, the basic principles of LAS technology and the LAT and LAI methods were discussed. Moreover, the research and application states of the LAT and LAI methods at home and abroad in the past decade were mainly introduced, including linear and nonlinear measurements of LAT and 2D/3D imaging of LAI. Finally, the perspectives and trends of LAS-based 2D/3D imaging technology were reviewed.

In recent years, with the rapid development of modern industry, the non-contact measurement technology has attracted more and more attention. As an interferometric measurement technique, the laser Doppler vibration measurement can be applied to application scenarios where it is difficult to obtain vibration measurements through accelerometers or other surface contact sensors. Since the birth of the laser Doppler vibrometer (LDV) in 1983, it has gradually become the most widely used non-contact vibration measuring equipment in various fields due to its advantages of high precision, high efficiency, and portability. Based on the analysis of the basic principles of LDV, this paper discusses the applications of LDV in agriculture, life medicine, aerospace, and construction engineering in recent years.

Starting from the superhydrophobic theory, the importance of material surface roughness and solid-liquid contact area for the preparation of superhydrophobic surface based on three typical basic wettability models is revealed in this paper. On this basis, the advantages and disadvantages of direct laser writing (DLW), direct laser interference patterning (DLIP) and laser induced periodic surface structure (LIPSS) methods are reviewed. Among them, high-energy-density laser pulses are used to ablate the surface of materials in DLW method and it can construct any three-dimensional structure on the surface of various materials because of its high degree of freedom, but its surface processing accuracy is poor, and it is difficult to build multi-level structure. DLIP method removes the surface material selectively with the interference patterns formed by multiple coherent lasers such that a finer periodic, three-dimensional, and micro-nano hierarchical structures can be directly defined on substrates. LIPSS method can obtain a large number of ripple structures with spatial period of hundreds of nanometers on the surface of materials, but the corresponding processing time will be longer. Finally, different fabrication methods of superhydrophobic surface are summarized from the aspects of preparation parameters, surface structures and morphologies, and hydrophobic properties. In addition, the research status and development direction of these methods are analyzed and discussed.

Femtosecond laser-assisted chemical etching technology has unique advantages in high quality, high depth to diameter ratio and high controllability of microporous processing, which provides a new way and method for the preparation of microporous. It has great application potential in micro total analysis system, three-dimensional optical flow control system in optical fiber and resonator manufacturing. In this paper, the research progress of femtosecond laser-assisted chemical etching for transparent media materials in recent years is reviewed, including the effect of femtosecond laser-modified zone on etching rate, the effect of strong acid and strong alkali chemical solution on etching effect, the optimization of chemical etching process, and the application of femtosecond laser-assisted chemical etching. The challenges faced by femtosecond laser-assisted chemical etching of microchannels, structure processing mechanism, and technology are summarized, and the research focus in the future is prospected.

T-type phase change memory has the advantages of low power consumption, non-volatility, high storage density and high reliability, so it is considered by the International Semiconductor Industry Association to be one of the mainstream products of the next generation semiconductor memory. In order to ensure the controllability of the manufacturing process of T-type phase change memory, a method for measuring three-dimensional morphology parameters of nanostructures based on optical scattering is proposed in this paper. The optical characteristic model of T-type phase change memory is established based on the rigorous coupled wave analysis method. The amplitude and phase change of elliptically polarized light on the sample to be measured are analyzed. The inverse scattering problem is used to solve the three-dimensional morphology parameters of the nanostructures to be measured. The three-dimensional morphology parameters of T-type phase change memory are measured by optical scatterometer, and the extraction results of the parameters to be measured are compared with those of scanning electron microscope. The feasibility and effectiveness of optical scatterometer in T-type phase change memory morphology characterization and manufacturing process monitoring are verified.

To solve the problems of poor quality and yield of camellia oil owing to the lack of basis for determining the maturity of camellia seeds during the process of harvesting, a method for detecting the maturity of camellia seeds based on mid- and far-infrared spectral data fusion was proposed herein. A Fourier transform infrared spectrometer was used to test the mid- and far-infrared spectroscopy data of camellia seeds with different oil contents at different maturity stages. Various feature extraction methods (principal component analysis, successive projection algorithm, and noninformation variable elimination method) were used to extract the original spectral data, and the methods were combined with a support vector machine algorithm (SVM) to develop a model for identifying the maturity of camellia seeds. The results show that the best discrimination accuracy in the mid-infrared band is 93.33% when using the successive projection algorithm combined with the genetic algorithm to optimize the SVM model. In the far-infrared band, nine variables extracted using the principal component analysis are used as input variables, and when combined with the SVM model optimized by the genetic algorithm, the identification accuracy of 96.67% is attained. The identification model of camellia seed maturity is established using the SVM algorithm after parameter optimization. The experimental results show that the accuracy of intermediate data fusion combined with the optimized SVM algorithm can reach 100%. The results of this study show that when combined with an improved SVM model, the infrared spectroscopy can accurately determine the oil content of camellia seeds. Data fusion can effectively increase the spectral information and remove redundant information from a single spectrum. The results can provide a reference to determine the best picking time of camellia and can be extended to determine the maturity of other agricultural and forestry products.

To obtain a high precision spectrum, the interferogram of space heterodyne spectrometer should be corrected. This study proposes a correction method based on the Fourier transform to address the nonuniform distortion of the interferogram caused by defects in a spatial heterodyne spectrometer. The target spectrum is discovered theoretically to be the convolution of the Fourier transform of the nonuniform distortion and the distortion spectrum. A verification experiment os performed by taking the continuous optical water vapor interferogram as an example. The results show that, among 2693 sets of experimental data, 2679 sets of data obtained an obvious correction effect. The standard deviation of 3 sets of randomly selected data after a correction increased by the order of magnitude, which verifies the effectiveness of the correction method.

In this paper, we use the terahertz time-domain spectroscopy system to measure the terahertz absorption spectra of three common food additives, namely, benzoic acid, sorbic acid, and xylitol, along with their mixtures. In addition, we select three machine learning algorithms to analyze the binary and ternary mixtures of food additives, namely, the partial least squares regression (PLS), the least squares support vector machine (LS-SVM), and the backpropagation neural network (BPNN). We find that in the quantitative analysis of multivariate mixtures, the nonlinear models LS-SVM and BPNN are more advantageous than the linear model PLS. As the mixture composition increased, the advantages of using a nonlinear model for analysis become more obvious. Among the two nonlinear models, we find that LS-SVM has a fixed modeling step compared with that of BPNN and does not require complicated parameter discussion and optimization, which can efficiently realize the quantitative analysis of multivariate mixtures. Moreover, by observing the spectral characteristics of the analyte, it is found that in addition to the discussion of the applicability of the algorithm, the spectral characteristics of the analyte also affect the accuracy of quantitative detection to a certain extent.

In this paper, ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy and Raman spectroscopy are used to investigate the spectral characteristics of seawater-cultured golden pearls with varying saturations of golden color produced from Pinctada maxima (hereinafter referred to as golden pearls). The results show that there are characteristic absorption peaks at about 360 nm and 280 nm in the UV-Vis diffuse reflectance spectra corresponding to the golden pearls and the absorption intensity at 360 nm is positively correlated with the golden saturation of the golden pearls. There is a negative correlation between the absorption intensities at 280 nm and 360 nm. The deeper the golden color on the pearl surface, the stronger the absorption at 360 nm and the weaker the absorption at 280 nm. Conversely, the weaker the gold color, the weaker the absorption at 360 nm and the stronger the absorption at 280 nm. Then, Raman spectra of pearls are obtained using excitation light sources with wavelengths of 405 nm, 532 nm, and 785 nm, respectively. Under the same laser wavelength, the characteristic peaks of the biological aragonite at approximately 1086 cm-1 and 705 cm-1 in the pearl, especially in the range of 100-300 cm-1, gradually appeare and increase in intensity with increasing laser energy (0.05%-100%). At the same time, under the laser light sources of 405 nm and 532 nm, two wide Raman peaks are observed in the range of 1300-1600 cm-1. Interestingly, with increasing laser energy, the intensities of the Raman peaks increase and the directional frequency shift occurs in the above two characteristic peaks. In addition, when the laser energy is low, the intensity of the Raman peak of aragonite at approximately 1086 cm-1 is significantly higher than that of the fluorescence peak caused by organic matter in pearl. With the increase of laser energy, the irradiation damage of the laser beam to the surface of pearl samples becomes more and more obvious. This research work can provide theoretical and technical support for the formation properties of current golden pearls and the identification of imitation golden pearls, and has certain reference significance for Raman spectroscopy in the detection and identification of other gemstones.

Classifying laser-printer toner is an essential step for identifying printers and dictating forged documents. However, the existing methods require numerous training samples, which is unrealistic in document examination cases. A few-shot classification method based on infrared spectroscopy and chemometrics is proposed. The infrared spectrum of eight types of toner was collected, and optimal spectroscopic data preprocessing methods were selected according to the data’s characteristics and traverse comparison experiment. Using the processed data, a partial least square-discriminant analysis (PLS-DA) model was established. Random forest (RF) and support vector machine (SVM) were used as the comparison methods. Experimental results show that the second derivative and Savitzky-Golay smoothing are the best preprocessing methods for the collected spectrum. In all conditions, PLS-DA outperform RF and SVM. When the number of the training set is larger than 90, the accuracy of the PLS-DA model is 100%, and when the number of the training set is 60, it reduces to 95%. The discriminant model of laser-printer toner based on infrared spectroscopy and PLS-DA exhibits high accuracy and strong interpretability, requires less training samples, and can be applied in forensic science.

LaTiO3 (H4) films were prepared using ion-beam-assisted electron beam evaporation. The effect of substrate temperature, ion-beam density, high-temperature annealing, and plasma post-treatment on the optical properties and surface topography of the H4 films were tested. Results show that increasing the substrate temperature and ion-beam density appropriately can improve the refractive index and film quality. Under 175 °C substrate temperature and 120 μA/cm2 ion-beam density, the refractive index of the H4 films can reach 2.70. Moreover, annealing and plasma post-treatment can further improve the film quality. The optimized process parameters were used to prepare high reflection (HR) films with H4 for a 980-nm laser diode. The HR films with H4 exhibit the best laser damage resistance under 600 MW/cm2 laser power density when compared with the HR films made with Ta2O5 or TiO2 as high-index materials.

Most flexible thin-film transistors employ plastic substrates instead of glass substrates, increasing white pollution. In this study, the flexible substrate is degradable nanocellulose paper, which has excellent smoothness with a roughness of only 3.12 nm that only increases to 6.03 nm after fabricating the entire device. Notably, the active layer of the paper-based thin-film transistors prepared using magnetron sputtering is IGZO/Al2O3. Therefore, the device can be fabricated at room temperature without undergoing thermal annealing, overcoming the limitation of nanopaper’s inability to withstand high temperatures. Al2O3 acts as an electronic bridge in the active layer, connecting the discontinuous indium gallium zinc oxide (IGZO). Furthermore, because IGZO is weakly crystalline, numerous carriers can circulate along the channel. The paper-based device exhibits excellent performance with a mobility of 22.5 cm2/(V·s), an on-off ratio of 5.07 × 106, and a threshold voltage Vth of -0.036 V as well as good stability at positive and negative bias voltages. This paper-based thin-film transistor has great potential for applications in the green and flexible display industry.

In order to obtain high-quality films and reduce experimental costs, β-Ga2O3 films were synthesized on mica substrates by chemical vapor deposition using GaTe powder as the Ga source. High crystalline quality β-Ga2O3 thin films were obtained by changing the growth temperature, buffer gas, and growth time, which were confirmed by X-ray diffraction (XRD) and Raman spectroscopy. XRD results showed that the optimal growth temperature of the film was 750 ℃. A comparison of β-Ga2O3 films synthesized under different buffer gases revealed Ar to be the best environment for growing film materials. The growth time of the thin films was changed under an Ar atmosphere to achieve β-Ga2O3 thin films with high crystalline quality. XRD results showed that the thin film with a growth time of 20 min had high crystalline quality. Finally, it was transferred to a Si/SiO2 substrate with a 300 nm thick oxide layer and tested by atomic force microscopy to obtain a 16 nm thick two-dimensional Ga2O3 film.

This study proposes an algorithm for predicting objects' reflectance based on the color digital camera raw data under multi-light source. The color digital camera's sensitivity functions and each light source's spectrum are measured, and the basic linear equation linking the camera raw data under multi-light source and object reflectance, including the system noise term is developed. The training color card (X-Rite 140 color card) is employed to estimate the system noise, and the multi-light source Wiener estimation algorithm is used to predict the reflectance. Two different brands of professional digital cameras are used to evaluate the algorithm. The findings demonstrate that the algorithm has the best performance under D65, U30, and HZ light sources. The Canon and Nikon cameras exhibit higher prediction accuracy for the Munsell color chart compared with the spectral reflectance obtained by the spectrophotometer, and the average CIELAB color difference is 1.59 and 1.40, respectively. It has crucial applications value in the fields of noncontact color measurement and color reproduction.