This PDF file contains the front matter associated with SPIE Proceedings Volume 13492, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Discrete particles randomly distributed in the ground-space link significantly impact laser signal transmission. Studying their scattering fields is crucial for laser speckle imaging and weak signal detection. This paper uses Mie theory to derive the statistical characteristics of scattering fields from laser-particle interactions, providing expressions for second and fourth-order statistical properties and the intensity fluctuation correlation function. Numerical calculations were performed on the mean function, correlation function, and intensity fluctuation cross-correlation function for a Gaussian-distributed rarefied particle group, considering particle radius changes. Results show that particle scattering fields have inherent correlation, which increases with particle size and shows periodicity. This correlation is largely independent of the particle's distance from the observation point, while particles at different locations exhibit high correlation for larger sizes. When the particle radius is near 0.2 mm, the speckle intensity cross-correlation function approaches 1. This research enhances our understanding of laser speckle imaging and weak laser scattering signals, aiding the development of more efficient optical communication systems and laying a foundation for future studies on laser speckle characteristics.

Continuous sign language recognition has received widespread attention in the field of human-computer interaction. Compared with optical camera based continuous sign language recognition systems, millimeter wave radar based sign language recognition systems have unique advantages such as high integration, all-weather operation, and robustness in low light environments. This study constructed a continuous Chinese sign language recognition method using 60GHz Doppler radar, which utilizes a convolutional neural network incorporating Efficient Channel Attention (ECA) to process radar micro Doppler signals. A sign language radar data acquisition device was established on the Doppler radar, and 20 commonly used sign language statements for train stations were collected in the time-frequency domain to form a dataset. Subsequently, these data were input into the proposed neural network model for recognition and classification. The experiment shows that the proposed system achieves an accuracy of 97.92% in recognizing sign language at train stations. Compared with other radar based sign language recognition systems, the proposed system exhibits higher recognition accuracy.

We introduce novel pump layouts for thin-disk lasers that maximize the number of passes while maintaining a fixed pump module size and moderate pump source quality. These advanced layouts are based on a nested multi-pass optical system, achieved by adding a series of deflecting prism pairs to ensure a uniform and compact beam distribution. This innovative approach not only increases the number of pump passes but also significantly enhances the overall efficiency of the laser system. As a result, it becomes feasible to use active materials with lower absorption rates, which are typically challenging to employ in standard designs. The main advantage of our method lies in its ability to minimize the typical increases in overall size and the stringent pump source quality requirements that are often associated with conventional multi-pass pump designs. By optimizing the optical arrangement, we ensure that the enhanced performance does not come at the expense of increased system complexity or footprint. This makes our design particularly suitable for industrial applications where space, cost, and reliability are critical factors. Furthermore, the use of commercially available pump optics, combined with the additional deflecting prism pairs, provides a practical and scalable solution that can be readily implemented. Our novel pump layouts thus offer a significant advancement in thin-disk laser technology, paving the way for more efficient and compact laser systems that can meet the demands of various industrial applications.

Visual inertial odometry (VIO) requires accurate initial parameters before navigation, such as the system's initial pose, scale information, and inertial measurement unit (IMU) biases. Consequently, rapid and precise initialization is crucial for ensuring the smooth progress of subsequent navigation. However, when the system is in an environment lacking visual features, the system without measurement constraints will rapidly diverge. During this period, due to the unknown motion state, static initialization cannot be performed. To ensure that the system can navigate through this period as smoothly as possible and restart VIO, this paper proposes a dynamic initialization method for visual inertial odometry based on deep learning. This approach relies solely on inertial data, using a deep learning network to learn attitude errors and uncertainties, which are then utilized as measurement values and combined with an extended Kalman filter (EKF) to correct the system state. Experimental results on a public dataset show that the proposed method enables rapid dynamic initialization under short-term visual measurement absence, and effectively improves the system's attitude accuracy. Compared to the method of traditional inertial navigation solving after gyroscope calibration, the heading error of our proposed method is reduced by 13.38%.

The pulse compression grating is one of the core components of the chirped pulse amplification system, and its performance determines the performance and lifetime of the entire laser system. Previous studies have shown that the transmission grating is limited to a single material, and the groove depth of the grating is too deep to achieve high diffraction efficiency, making it difficult to fabricate. In this paper, a multilayer dielectric film transmission grating is designed for pulse compression. The grating with 1740 lines/mm and the central wavelength of incident light is 1060 nm. Six layers of dielectric films are added between the grating region and the substrate, with Ta₂O₅ (n=2.10) and SiO₂ (n=1.45) as high and low refractive index materials. The structure of the dielectric film transmission grating is optimized based on the Rigorous Coupled Wave Analysis (RCWA). The results show that when only considering diffraction efficiency, the - 1st order diffraction efficiency at a center wavelength of 1060 nm can reach 99.94% when the grating groove depth is 1.164μm and the duty cycle is 0.324; the -1st order diffraction efficiency in the wavelength range of 1042-1078nm can reach 95%. Through electric field analysis of the grating, an electric field enhancement phenomenon occurs at the grating ridge, with a maximum electric field intensity (normalized |E/E₀|) of 1.296. Then, the electric field and diffraction efficiency are optimized, resulting in a grating groove depth of 1.106μm, a duty cycle of 0.446, a -1st order diffraction efficiency of 98.26% at the center wavelength of 1060nm, and a -1st order diffraction efficiency of 95% in the wavelength range of 1038-1086nm. The maximum electric field amplitude is 1.183. The grating after modulation of the electric field increased the bandwidth from 36 nm to 48 nm, the diffraction efficiency decreased by 1.68%, and the maximum value of the electric field amplitude decreased by 8.71%.

Ice clouds have a high coverage on the Earth's surface and significantly impact the Earth's energy balance, climate change, and weather evolution. The brightness temperature in the terahertz band is highly sensitive to the main detection factors such as ice-water path and ice particle size, making it the optimal frequency band for ice cloud detection. Against the backdrop of ice cloud detection, an airborne terahertz ice cloud detector has been designed and developed. The radiometer system utilizes a full power type with periodic calibration, the antenna subsystem employs a plane mirror antenna and quasi-optical feed network for feeding and receiving, and the receiver subsystem adopts a direct mixing reception mode. The performance indicators of the system have been tested and verified, with results showing that the system performance meets the requirements of ice cloud detection.

With the continuous development of infrared detection equipment, higher requirements are put forward for the survivability of various weapons and equipment. Infrared stealth technology can reduce or control the infrared radiation of the target, shorten the distance and reduce the probability of being discovered, and improve the survivability of the target. In recent years, the rapid development of electrochromic technology provides a new idea for the regulation of infrared emissivity. Under the action of low electric field, electrochromic materials can realize reversible and stable regulation of optical properties (transmittance, absorptivity, reflectivity, etc.) in a wide spectral range (visible light and near, middle and far infrared), and have the advantages of low energy consumption, rapid response, stable cycle performance, etc., and the available infrared electrochromic materials system is rich. Therefore, electrochromic technology can be applied to dynamic infrared stealth, which can adapt the target to the change of environmental background, and has important application prospects in infrared stealth and camouflage.

In order to cooperate with algorithm debugging and internal field testing of an imaging system, a front-end simulator was designed to provide excitation signals for a multi aperture imaging system. Visual simulation technology was utilized to simulate the functionality of the front-end of the imaging system. The dual channel FC cards was employed to simulate the communication between the front-end and ICP. The communication efficiency between front-end and ICP, multi-channel image alignment algorithm, object detection algorithm, and error response of the system were tested by the simulator in the hardware in loop mode.

Image registration is the process of geometric calibration of two or more images with overlapping areas of the same scene from different perspectives, different sensors or acquired at different times. This article focuses on the registration problem of sub-pixel displacement images in the process of super-resolution image reconstruction. Two sub-pixel image registration methods are introduced, including the spatial domain based feature matching SIFT registration method and the frequency domain based Vandewalle registration method. Four low resolution sequence images obtained through a micro scanning camera are used to simulate and analyze the registration accuracy of the two algorithms. The results show that both algorithms can achieve sub-pixel level registration of low resolution images.

The current research status of micro scanning imaging technology is discussed in this article. It analyzes the basic principles and implementation methods of micro scanning imaging technology, the factors that affect the effect of microscanning super-resolution imaging. The results indicate that scan step size, registration algorithm, and reconstruction algorithm are the main factors affecting micro scanning super-resolution imaging. Changing the mode of micro scanning(reducing scan step size), improving the registration accuracy of registration algorithm, and improving the accuracy of reconstruction algorithm can improve the effect of super resolution. Finally, the low resolution images collected in2×2mode are reconstructed using POCS algorithm, and the improvement ability after micro scanning is calculated.

In this paper, we review pointing, acquisition and tracking (PAT) technology in inter-satellite laser links. Firstly, the structure of the PAT system is introduced, and the operating principle and the established procedure are also thoughtfully explained. Then, the optimization methods of the PAT technology are summarized following the three aspects: the building time for the link, the link stability and the beacon-free operation. In these methods, the complex communication environment as well as the device size and the data transmission rate are fully considered. Finally, we also list the latest laser terminal products, where the PAT technology implements on.

In view of the lack of fine ground detection data of freezing rain clouds, using the high sensitivity of Ka band cloud radar for small-scale precipitation particle detection, combined with ground meteorological automatic observation equipment, a joint quantitative detection experiment was carried out on the vertical structure of cloud in the whole process of freezing rain in Changsha, Hunan Province from 00:00 on February 5 to 24:00 on February 7,2024 (for simplicity, it is called "2.5" process). On the basis of the quality control of the basic data, the vertical spatiotemporal structure of the four physical parameters of cloud reflectivity factor Z, radial velocity V, velocity spectral width W and linear depolarization ratio LDR in the whole process of freezing rain generation and dissipation were successfully obtained by using the echo feature processing method. The analyzed results show that the type of this freezing rain belongs to the mechanism of ice phase formation, and there are obvious melt layer characteristics, and the Z, V, W, and LDR increase significantly from 3km height to the ground, and the peak LDR reaches -15dBz~-20dBz.the vertical profile structures of Z, LDR and V before and after the freezing rain are more similar than those of ordinary winter sleet, however ,the vertical profiles of V and W are quite different from those of sleet. The results are helpful for the identification of the formation mechanism of freezing rain and the extraction of freezing rain feature parameters and early warning.

Space-based Earth observation systems play a significant role in national economic development and national defense security. To achieve all-weather, near real-time integrated observation services encompassing land, sea, air, and space, satellite mission planning systems are evolving towards intelligence and autonomy. This study constructs three typical space-based Earth observation intelligent agents. The intelligent agent models integrate deep learning and reinforcement learning algorithms, and their performance is validated through simulation using reward functions. This research proposes an intelligent agent-based decision support technology aimed at enhancing the efficiency and effectiveness of space-based Earth observation technology. Experimental results show that the intelligent agent-based decision support technology can effectively integrate multi-source observation data, respond quickly to user needs, provide high-quality decision support, and significantly improve the autonomy and intelligence level of satellite mission planning systems.

Photoelectric platform has important applications in many fields, and the spatial orientation ability is an important function of photoelectric platform, when used in industrial and military areas. As the encoder is a key component in the control loop of the Photoelectric platform, different encoder principles bring different application methods, and a variety of interface forms have to be considered when design the Photoelectric platform. The traditional method is new hardware for each new platform, so there is duplicate design among projects, and the design of multi-axis platforms with multiple interfaces will be more complicated. This article tries to tackle the communication problem of control board with multiple types of encoder with none or little hardware modification. In this paper, the hardware and protocol characteristics of three common encoder interfaces, including ENDAT, SSI and UART, are studied, and an encoder interface control scheme suitable for multi-axis platforms is proposed and verified, which takes FPGA as the core ,can support communicating with multiple devices asynchronously at the same time, and brings good scalability. In this paper, the communication capability of this scheme ,with three common interfaces ,is verified, and ENDAT and SSI timing rates are above 1Mhz, and the maximum baud rate of UART is 921600bps.

With the continuous advancement of constellation remote sensing technology for observing star clusters, in recent years, researchers both domestically and internationally have been increasingly focusing on the application of Synthetic Aperture Radar (SAR) observations from multiple stars. However, even with constellations having hundreds of satellites, individual calibration is still required for each satellite during radiometric calibration. Due to different imaging parameters of various satellites, this may lead to differences in the grayscale values of imaging results in overlapping areas, adding complexity to data fusion and applications. Therefore, there is currently a lack of a technical solution for evaluating the radiometric consistency of multi-star SAR. To simplify the complexity of radiometric calibration evaluation and address the challenge of assessing radiometric consistency due to differences in viewing angles in multistar data acquisition, this paper proposes a homogeneous region-based method for evaluating radiometric consistency among multiple stars. By segmenting the entire SAR image into superpixels and selecting long-term stable features such as urban areas, roads, grasslands, and bare soil for radiometric consistency evaluation. The evaluation results show that the average energy standard deviation for urban areas is 0.9524, and for bare soil is 0.4821, indicating higher radiometric consistency for single stars under the same incidence angle. When verifying the radiometric consistency among multiple stars using Sentinel-1 and TerraSAR satellites, this paper employs the Ulaby model to correct the backscattering coefficient of the TerraSAR satellite, reducing the calibration error from 1.78 dB to 0.63 dB. Through this correction, the impact of observation angle differences on the backscattering coefficient of SAR data is eliminated, ensuring that the radiometric consistency evaluation results are only influenced by the accuracy of satellite radiometric calibration, thus making the evaluation results more reliable.

We have demonstrated wideband tunable optical parametric oscillator (OPO) based on BaGa₄Se₇ crystal. A pump doublepass, short cavity, singly resonant OPO configuration was used to improve the optical conversion efficiency and reduce the OPO threshold. Using a commercial nanosecond laser with a repetition rate of 10 Hz as the pump source, the tuning range of BaGa4Se7-OPO achieved 3.10-4.84 and 8.24-13.34 µm in mid-wave and long-wave infrared band respectively. The maximum single pulse energy of reached 8.55 mJ at 3.88 µm and 0.855 mJ at 10.8 μm. To achieve high repetition rate operating, an electro-optic Q-switched laser with repetition rate of 1 kHz was built. The high repetition rate BaGa₄Se₇- OPO have a maximum output power of 564 mW at 3.87 μm and a tuning range of 2.99-5.04 µm.

We will present our proposal for a low-coherence laser facility - 'kunwu' - based on neodymium glass amplification of super-luminescent light pulse(SLP) with ~3.5 THz (13nm) bandwidth, and the beam has been converted to second harmonics before focusing on the target. We are validating the output capability of the laser (>10J/cm2@1ω) and improving the beam quality to achieve a more smoothing focal spot. We believe that this is a very ideal driving laser for laser inertial confinement fusion, and the scheme is very likely to be the best choice for the development of high-power laser drivers.

This paper integrates the background of holographic interference and, based on Real-time coherence holography, proposes a method for extracting and restoring phase distortion in underwater turbulence images. By contrasting holographic interference under weak to strong oceanic turbulence (using a plane light wave through a static water region as a reference light source). Extracting complex amplitude information from multiple holograms, the phase information is transmitted to the spatial light modulator (SLM) to output phase-conjugate light waves, effectively compensating for wavefront distortions caused by the scattering medium, achieving the reconstruction of the target beam. This approach circumvents the utilization of costly wavefront sensors and effectively rectifies phase distortion in turbulent environments, thereby yielding more precise and lucid imagery. Consequently, it exhibits significant potential for practical applications.

In recent years, the scale of space-ground systems has been continuously expanding, and data acquisition capabilities have experienced explosive growth. The large-scale Aerospace observation data provide the research foundation for the application of artificial intelligence technologies in the field of intelligent interpretation. However, the current business workflow and practical applications of Aerospace Intelligent Interpretation still have significant shortcomings, such as insufficient timeliness and weak target detection capabilities, which severely restrict the efficiency of Aerospace information acquisition. To address the current issues, this study proposes an Integrated Training-Inference Architecture for intelligent interpretation based on Aerospace Big Data. By constructing sample database, algorithm library, and visualization system supporting human-machine collaboration, this research proposes workflow which including algorithm recommendation based on collaborative-filtering, continuous iteration optimization and autonomous training of algorithm models, intelligent interpretation led by human-machine collaboration, and multi-task-oriented performance evaluation for intelligent interpretation. The process is verified through typical Aerospace Information Intelligent Application Tasks, demonstrating the feasibility of the Training-Inference Integration architecture in intelligent interpretation domain. By employing this method, the capability and efficiency of Aerospace Big Data Intelligent Interpretation have been effectively enhanced, enabling the proactive release of intelligent algorithms services and achieving human-machine collaboration mode in intelligent interpretation tasks.

In view of the characteristics of the test platform of vacuum capability evaluation for laser thruster, which have such difficulties as high vacuum degree, adjustable- cubage quadrate container, the seal design for horizontal and vertically moving port, etc. The test system is composed of adjustable-cubage quadrate container, vacuum system, mass spectrum device, mobile port, and control system. The device was achieved high degree of vacuum by dry pumps and molecular pumps. Residual gases were analyzed by mass spectrum device. Quadrate vacuum container obtained adjustable-cubage and seal capability by mobile port. The degree of vacuum 5.0×10^-4Pa is achieved. In addition, Leakage of 1.0×10^-8Pam³/s is obtained, and such residual elements as carbon, hydrogen, nitrogen, oxygen, were analyzed, vacuum and optics experiments were carried out, and the security and reliability were guaranteed.

Near space is an important airspace of the earth’s atmosphere. Detecting the characteristics of the atmospheric environment in the near space is the key to understanding the laws of atmospheric evolution. rocket dropsonde is an important means of sensing the pressure and temperature of near space in situ. and the data acquired by rocket dropsonde is influenced by the dynamic airflow. Herein a compensation method towards a kind of rocket dropsonde is presented and the feasibility is verified. A fluid-structure couple simulation towards the rocket dropsonde is run, and the results are discussed. The relationships between dynamic pressure, dynamic temperature, velocity and total pressure are come up with as the compensation for the rocket dropsonde.

Raman fiber amplifiers (RFAs), as a new type of laser capable of achieving both high power and special wavelength output, have been widely adopted in energy, environment, and industry. However, the generation of high-order Stokes reduces the conversion efficiency of this laser and limits its further power scaling. In this work, we utilized two seed lights operating different wavelengths for Raman amplification and investigated the impact of the power ratio of the two seed lights on the evolution of the higher-order Stokes spectra. The modulation of the higher-order Stokes spectra is achieved for the first time. Based on this experimental scheme, we successfully achieved effective suppression of the higher-order Stokes and obtained 1100W Raman laser output. The findings presented in this study may provide a new approach for further power scaling of RFAs operating special wavelength.

Suppressing Yb-ASE to overcome the bottleneck effect is the key to optimizing the efficiency bottleneck of the Erbium-Ytterbium co-doped fiber amplifier (EYDFA). In this work, we use three typical commercial laser diodes (LDs) as pump sources to experimentally compare the efficiency with variations of pump wavelength in different fiber lengths. We found that the optimal pump wavelength of EYDFA has a blue shifting with the increment of gain fiber length. The functional relationship between the optimal pump wavelength and the length of gain fiber is predicted according to the experimental results. If the fiber length increases over 20 m, the amplification efficiency under 940 nm-LD pumping conditions is better than other pumping sources. It is necessary to consider appropriately extending the fiber length to optimal efficiency using a pump source with an offset pump wavelength (such as a commercial 940-nm LD). This work provides a reliable technical reference for the practical fabrication of high-power EYDFA.

The residence time of fuel in the scramjet engine is generally on the order of milliseconds. Achieving efficient mixing of fuel with the mainstream flow within such a short time poses challenges for combustor mixing efficiency, making enhanced mixing methods a focal point of research. Cavity coupled upstream transverse jet injection, as a common combination passive mixing enhancement method, not only enhances mixing efficiency and stabilizes flames but also avoids excessive total pressure loss. This study utilized Nano-tracer-based Planar Laser Scattering (NPLS) technology to obtain detailed structural images of the upstream transverse jet injection flow field in the concave cavity, determining the penetration depth of the jet. Additionally, using the NPLS system, the velocity field of the mixed flow was computed through Particle Image Velocimetry (PIV) techniques.

L band aperture synthesis microwave Radiometer (LASMR) on board Chinese Ocean Salinity Mission(COSM) is a two-dimensional interferometer, which, due to the Fourier-transform relationship between the spatial domain and the brightness temperature, possesses a well-behaved redundancy characteristic. The analysis results show that when the failed units are located on long baselines, the more units that fail, the greater the decrease in system resolution, while if the failed units are on short baselines, the impact on system resolution is relatively minor. LASMR improves resolution by synthesizing the aperture but worsens sensitivity, hence when there are unit failures, the system’s noise floor is reduced in most cases, showing a trend towards optimization. The absence of long and medium baselines has a minor impact on the quality of the brightness temperature image, while the lack of short baselines significantly affects the image quality, leading to a rapid deterioration in image accuracy. However, under fixed unit failure conditions, the impact on images for different targets is biased in effect. The error correction of the brightness temperature can be performed using the ocean target transform (OTT) technique, and the image accuracy is significantly improved. Even under the adverse condition of 15 unit failures, the image accuracy can still reach 0.12K. The redundancy characteristics of the LASMR are evident.

1319 nm laser has important applications in fields such as fiber optic communication, laser medicine, laser color display, medical imaging and public safety. In addition, 1319 nm laser and Nd:YAG main spectral line 1064 nm can obtain 589 nm yellow light that resonates with sodium atoms through nonlinear-optics sum frequency generation, which has been successfully applied in adaptive optical systems. For uniformly widened Nd:YAG 1319 nm transitions, using a standing wave cavity will result in spatial hole burning effect, causing longitudinal non-uniformity in the intensity distribution inside the cavity. As the pump power increases, the spatial-hole burning effect will cause multiple longitudinal mode oscillations, resulting in broadening of the laser spectral line. Suppressing the multi longitudinal mode oscillation in the standing wave cavity with an etalon will cause a significant increase in cavity loss, resulting in a decrease in output power. The ring cavity enables the laser to operate in a traveling wave manner, eliminating the spatial-hole burning effect. When a certain longitudinal mode vibrates inside the cavity, it will consume the gain of other longitudinal modes, thereby suppressing the oscillation of multiple longitudinal modes. Therefore, it is widely used to obtain narrow-linewidth laser output. A three-mirror ring cavity with 808 nm semiconductor laser side pumped Nd:YAG crystal is used to obtain a tunable 1319 nm laser with high power and high beam quality. Inhibition of 1064 nm and 1338 nm spectral line oscillation in Nd:YAG is achieved through cavity mirror coating and insertion of an etalon, respectively. The Faraday rotator, half wave plate, and polarizer form a unidirectional device that allows the laser to operate in one direction. When the LD pump power is 96 W, a 1319 nm polarized laser output with an average power of 10 W is obtained under thermal near unstable cavity operation conditions, and the beam quality factors are M²_x = 1.20 and M²_y= 1.26. By precisely controlling the temperature of the etalon, the laser wavelength can be finely tuned from 1318.888 nm to 1319.358 nm with a tuning range of 470 pm (81 GHz) and a tuning accuracy of 0.7 pm (125 MHz).

This paper presents the development of an (8+1)×1 pump-signal combiner with high pump coupling efficiency and negligible beam quality degradation. Compared to conventional (6+1)×1 combiner, the developed (8+1)×1 combiner features a smaller space occupancy for individual pump fibers, which makes the pump sources less prone to being affected by cladding light in the counter-directional pumping configuration. It also has a larger space occupancy for the signal fiber, which ensures better preservation of beam quality. The fabricated combiner exhibits a pump coupling efficiency of 98.9 %, a beam quality degradation ratio of less than 3%, and a temperature rise coefficient of less than3 °C/kW without active cooling. When this combiner is used in a counter-directional tandem-pumped fiber laser, it allows for a high beam quality output that exceeds 10 kW.

Regenerative amplifiers based on thin-disk technology have a high-beam quality output laser due to their own excellent thermal management. Conventional thin-disk regenerative amplifiers are usually constructed in a stable resonator design with a long resonator length, which limits the practical application range and further industrialization. We report a compact thin-disk regenerative amplifier with an overall resonator length of less than 2.5 m that enables high-beam-quality laser output. Continuous laser output of 66 W when the resonator is 2.16 m. 59 W of a pulsed laser with a repetition rate of 50 kHz was output at a resonator length of 2.3 m. The thin-disk regenerative amplifier has the potential to output a laser up to 100 mJ while maintaining good beam quality

“Gou Mang” Terrestrial Ecosystem Carbon Inventory Satellite is China’s first forestry remote sensing satellite with an active LiDAR as the main payload. As the Active-passive payload, the multi-channel Carbon Sinks and Aerosol LiDAR(CASAL)’s stability of the receiving optical axis is one of the keys to success. Gravity is the key influencing factor, which is impacting on ground installation and testing results. Considering the consistency between the space and earth, it is necessary to ensure that the design minimizes impact of gravity deformation on the stability of the receiving optical axis. This article discusses the optimization design ideas of the optical and mechanical system, the analysis and experimental verification of the receiving optical axis of CASAL. The result indicates that the simulation analysis is consistent with the experimental verification result. Currently the CASAL is operating well in space. The information can provide helpful reference for subsequent loads.

In order to study the mechanism of laser on aluminum alloy surface microstructure, the effect of laser scanning speed on aluminum alloy surface microstructure was revealed. In this paper, combining experimental and numerical methods, has thoroughly investigated the laser ablation process on aluminum alloy surfaces. The calculated results of the model agree well with the experimental results in some respects. By manipulating scanning speed and spacing, we successfully prepared distinct surface microstructures on the aluminum alloy. The findings indicate that scanning speed significantly impacts thermal diffusion and ablation depth, while control over scanning spacing positively shapes the surface microstructure's morphology. At wider scanning intervals, the thermal diffusion and internal thermal stress can induce a 'warping effect' and material removal. Optimizing these parameters is crucial for the highest quality micromachining outcomes.

In the resonator of an actual laser oscillator, the complex-valued laser field is extracted from the gain. The propagation of light in a cavity is usually described using the Fast Fourier Transform (FFT). In this paper, a deep learning method based on physics-informed neural networks (PINNs) is introduced to implement the intracavity propagation of complex-valued lasers. The complex-valued laser field and partial differential equation are divided into real and imaginary parts because the optimizer of neural networks cannot deal with the derivation of complex values. A given paraxial wave equation is used as an example to validate the performance of the method. The results of the propagation of complex-valued laser from one interface to another within a cavity containing gain media are presented. The comparative analysis between the predictions yielded by PINNs and numerical solutions via FFT demonstrates remarkable accuracy, with L1 relative errors observed in the real and imaginary components of the laser field at 2.817% and 6.762%, respectively. Notably, the computational efficiency of the trained PINNs is pronounced, requiring a mere 0.43 seconds to reason the complex laser field at any given plane, in contrast to that of up to 17.6 seconds necessitated by FFT computations.

A temperature-independent humidity fiber Bragg gratings (FBGs) sensor based on graphene oxide film in dual-core fiber (DCF) has been demonstrated. FBGs are written by using the Ultraviolet (UV) exposure fabrication method through a phase mask on each core of a DCF, which was spliced to a standard single mode fiber (SMF) and tapered the splicing point. The cladding of the DCF was partially abraded so that one of the FBGs could be sensitive to changes in ambient humidity through the GO film. Another FBG is used as a reference to remove the effect of temperature crosstalk. The humidity sensitivity of ~5.582pm/RH% in the range of 45%-85%RH was obtained experimentally. This DCF FBGs sensor has a promising application in the field of temperature-independent parameter measurement.

We report a two-stage two-pass compact amplifier based on SrF₂ crystal with gains of over 10⁶. The shape of the crystal is irregular, so that the gain length is increased and parasitic oscillation is suppressed. The amplified spontaneous emission (ASE) and spectral characteristic of amplifier are analyzed. The results show that ASE increases with the pump power, and the simultaneous use of different crystals types can increase the output bandwidth. This work has a potential application in high-power / high-energy laser devices.

Brightness of single wavelength diode laser is limited to single chip and technology of beam space assembling. In order to improve the brightness of fiber coupled diode laser, two channels wavelength division multiplexing is employed to achieve power increased doubly but BPP (Beam Parameter Product) remained unchanged theoretically. According to Lang-Kobayashi rate equation and Lamb laser equation with external cavity feedback and coupled wave theory, method of spectral locking and Bragg diffraction has been established to support our optical and mechanical design. Laser operated at 976.5nm center wavelength is diffracting and 975.5nm center wavelength is transmitting through beam combing VBG, the spectrum of sub beam is locked to 0.3nm (FWHM), the combing spectrum is 976.5nm±1nm. The diffraction and transmitting efficiency are about 80%, 96% respectively. The power of beam combing can reached at about 800W, and the BPP is less than 15mm·mrad, which indicates that could be coupled to 200μm core diameter fiber, NA (Numerical Aperture) would be less than 0.15. The results could be benefit for high brightness pump source of fiber laser or direct LD (Laser Diode) applications.

Near-space atmospheric models play a crucial role in the advancement of hypersonic weapons. Current atmospheric models calculate air pressure using altitude back-calculation, but this method often falls short of providing the accuracy required for enhancing aircraft performance. This paper introduces an ultra-low pressure sensor based on Pirani's principle for in situ sounding rockets. The sensor is constructed on a silicon substrate and employs gold wires as the sensing element, featuring an initial resistance of 1100 Ω. It uses a photosensitive polyimide (PSPI) as the micro-hot plate material, which has an area of 1 mm x 1 mm. To meet the environmental requirements under high overload conditions, an aluminum film is integrated into the structure to improve its resistance to such overloads. Additionally, this paper conducts an analysis of the thermal conductivity model to enhance the structural integrity and performance of the Pirani vacuum sensor. Finally, This paper presents a comprehensive model correlating physical dimensions with detection performance and performs an analysis of thermal stress utilizing simulation software. Additionally, it includes an examination of electromagnetic coupling and thermal field effects on the designed Pirani vacuum sensor. During the rocket launch for deploying a probe sensor for sounding, the sensor experiences a longitudinal overload of 200g. Finite element analysis indicates that the stress exerted on the sensor is 3.2 MPa, significantly lower than the PSPI/Al composite film's Young's modulus. The simulation results indicate that the sensor measurement range can reach 0.037-3634Pa. When the measuring range is 0.1 to 100 Pa, the sensitivity reaches 136.7/log(P). And for a measuring range of 100 to 1000 Pa, the sensitivity is 24.9/log(P). The sensor’s sensitivity, range, and stress characteristics are adequate to meet the requirements for rocket sounding. This sensor offers a valuable approach for full-altitude in-situ detection of atmospheric pressure during rocket sounding, contributing to the establishment of accurate near-space atmospheric models in our country.

To address the issue of insufficient dynamic range in conventional camera imaging under high dynamic range scenes, a high dynamic range imaging method based on the digital micro-mirror device (DMD) has been designed. This method utilizes the DMD as an optical modulation device to modulate the incident light at the pixel level. Additionally, a continuous imaging image mapping method has been developed, enabling precise control over DMD to adjust the exposure levels of different pixels, thereby enhancing the system’s dynamic range. Mathematical logical deductions demonstrate that the theoretical dynamic range enhancement of the designed systems is directly related to the DMD control method. Experimental results confirm that the designed imaging method has the capability to increase the dynamic range by 58 dB.

Gain-switched mid-infrared 1 and 7 mol. % erbium-doped fluoride fiber lasers pumped at 1.7 μm were demonstrated. They delivered 2.8 μm pulsed laser with maximum average powers of 306 mW and 390 mW, respectively, corresponding to recorded laser efficiencies of 43.6% and 35.5%. This work exhibits the potential of the 1.7 μm pulsed pumping scheme for gain-switched 2.8 μm erbium-doped fluoride fiber lasers and this pumping scheme paves the way for high-efficient pulsed fiber lasers in the 3 μm region.

The process of online crystal alignment in high-power laser facilities is both challenging and labor-intensive. We propose an automated method for self-alignment of crystals on these facilities, utilizing machine learning. This method employs a machine learning algorithm running on a Raspberry Pi to automatically locate the reflective spot from the crystal's back surface and adjust its position to achieve self-alignment. The proposed scheme comprises two modules: a rectangular spiral spot scanning search method module and an automatic spot aligning method module based on the open-source machine learning algorithm M-LOOP. Initially, the rectangular spiral spot scanning search method is used to position the laser spot within the field of view of the CCD camera. The M-LOOP algorithm then automatically adjusts the laser spot to align with the reference center. The hardware system includes a crystal alignment optical system, motors, a CCD camera, and a Raspberry Pi. Offline experiments have demonstrated that this method can accomplish the automatic search and alignment of the crystal return spot of a He-Ne laser in approximately 10 minutes. This solution addresses the issue of traditional technology requiring manual search and adjustment of the crystal's reflection spot for self-alignment.

FX Cross correlation is a computation and memory intensive task; it is normally a bottle neck of signal processing in real time scenarios. As GPU is designed to process data in parallel, we decided to implement the algorithm on GPU for a better performance (comparing with CPU implementations). In this paper, we present 4 CUDA-based cross correlation implementations. The initial version did not perform very well. We then optimized it with share memory on GPU and improved its performance by a factor of 4. We then realized that we could get a better performance by doing cross correlation with optimized matrix multiplication CUDA libraries. In the end, we built two cross correlation pipelines with selected libraries (xGPU and tensor core) and compared their performance with our optimized one. We found out that these pipelines are much faster (the tensor core-based implementation is about 10 times faster) than our optimized implementation.

Tabletop high-energy repetition-rate picosecond lasers can be utilized to drive secondary radiation sources such as infrared lasers, facilitating more convenient and efficient research into attosecond pulses and high-energy density physics. Compared to Nd³⁺, Yb³⁺ have advantages including a small quantum defect (~9%), a longer fluorescence lifetime, high saturation fluence, high thermal conductivity of matrix crystal, and a wide range of doping concentration. The LD-pumped Yb³⁺-doped repetition-rate lasers possess a unique combination of pulse duration and energy, which confer an intrinsic advantage in the field of high-energy picosecond lasers. In this paper, we proposed a hybrid Yb³⁺-doped crystal as the gain medium, employing a multi-pass amplification configuration to achieve sub-picosecond laser output with a peak power exceeding 1 TW in 2 m³. This scheme can provide a new technical route for tens of TW high-energy picosecond lasers.

The shock wave system in supersonic flow fields is a critical factor influencing the quality of chemical laser beams. This study develops a comprehensive interpretation technique for supersonic flow field information by utilizing a deep learning method incorporating physical explanations. A compressible flow analysis framework of Physics-Informed Neural Networks (PINNs) is established for supersonic jets with a maximum Mach number of 10, combined with Planar Laser-Induced Fluorescence (PLIF) technology. This approach enables the reconstruction of velocity and temperature fields from concentration field measurement data. The proposed method achieves high accuracy in reconstructing data in the shock wave region, with relative L2 errors of 20.56% and 23.78% verified by Computational Fluid Dynamics (CFD) data. Experimental demonstrations showcase the ability of this method to reconstruct measured shock waves, providing an effective technical means for the comprehensive analysis of supersonic shock wave characteristics.

Laser has the advantages of high brightness and good directionality, which is used to interfere to optical imaging system, causing the sensor department pixels to saturate or damage, resulting in the loss of scene information and a significant reduction in the working ability of the system. In this paper, we used an estimate criterion combining the laser spot property and image feature distribution to evaluate the image with space background. The results show that the score obtained through this criterion are consistent with subjective judgment.

Aiming at the constraints of computing power and storage resources of embedded devices, this paper puts forward an improved model lightweight scheme, mainly introducing model distillation and model quantization methods. After L2 loss knowledge distillation experiment based on intermediate features, the accuracy of YOLOv5s model is improved by 1.6%. Through asymmetric quantization experiment of PTQ INT8, the speed is improved by nearly 2.6 times when the model accuracy is only 2.3%, which meets the demand of real-time reasoning. After the quantitative perceptual training, the speed of the model is increased by 1.8 times with a loss of only 1.4%. The improved lightweight model is deployed in embedded devices, and its performance is tested. Under the condition that the accuracy of the original model is 97% on RK3588S, the reasoning speed is increased by 2.6 times.

This Addressing the bottleneck issues such as the large infrared radiation dynamic range of aircraft plumes, the irregular multi-angle geometric shapes of jets, and the difficulty of long-range measurements, research on long-range high-precision infrared radiation calibration methods based on infrared spectroradiometers is conducted. The study delves into high dynamic range full-field-of-view multi-segment calibration methods and aperiodic transfer function (ATF) calibration methods for distant targets, ultimately establishing a set of high-precision radiometric calibration methods. The multi-segment spectral radiation calibration method combines the optical gain of the testing system, spectral splitting response, integration time, upper limit of dynamic measurement range, and the detectable radiation energy per pixel. This model quantitatively describes the nonlinearity of detector output and the measurement errors introduced by inaccuracies in the characteristic spectral segments. Moreover, this paper fully considers the point source image spot size and aberration diffraction point spread characteristics of the target in the detection unit of the infrared spectroradiometer. A high-precision calibration model for the ATF of the spectroradiometer is established to achieve high-precision calibration of the spectroradiometer. The research results will provide technical support for establishing comprehensive and accurate methods for infrared spectral radiation testing and evaluation.

In this study, a physical model of the supersonic flow chemical reaction and beam transmission in the laser cavity is established, and a numerical calculation is carried out based on the multiphysical field coupling method. The results show that the mismatch between the wall morphology and aerodynamic parameters is the main reason for the excessive power density of the laser spot. Furthermore, according to the calculation results, the surface type of cavity was optimized, and the near-field uniformity was effectively improved. The research results will provide a theoretical basis and design reference for chemical laser engineering applications.

Addressing the design requirements of infrared imaging systems for high luminous flux, compact structure, and temperature insensitivity in complex environments. In this paper, a large relative aperture athermalized infrared optical system with a wavelength range of 8~12μm, an F-number of 0.8, a clear aperture of 200mm, and a field of view of 10°×5° was designed by determining the passive athermalization mode and the structure form of the transmission optical system and introducing the aspheric surface type, and the image quality analysis was carried out at different temperatures. The design results demonstrate that within the temperature range of -40°C to 60°C, the MTF at 33.3 lp/mm exceeds 0.3 for all fields of view, and the RMS radius of the point spread function remains smaller than the Airy disk radius across the entire FOV. The achieved design boasts a compact structure, exceptional imaging quality, and effective athermalization, thereby fulfilling the design specifications. This work holds significant research value for advancing the development of wide-temperature-range, large relative aperture infrared optical imaging systems.

Due to polypropylene's significant absorption at the wavelength of 10.2 μm, there is a pressing demand for the 10.2 μm laser source in the field of polypropylene material processing. Based on the optimized coating of the output coupler and the theory of lasing spectroscopy, we established a seven-channel folded cavity radio frequency (RF) excited waveguide CO₂ laser with the output wavelength of 10.2 μm. The laser utilized a seven-channel folded resonant cavity structure. The total discharged length along the resonator is 2.8 m while the physical length of the waveguide in the resonator direction is 425 mm. By optimizing the working gas pressure, the distance between the mirror and the waveguide port, the transmittance of the output coupler, output power of 108.5 W was achieved. The optimal coupling efficiency is 50% @10.2 μm. The beam quality M² factor is less than 1.2. Since the laser has the features of compact design, good beam quality, and excellent power stability, it can be a preeminent illuminant for the processing of polypropylene materials.

Polarimetric inverse synthetic aperture radar (ISAR) offers continuous, all-weather space surveillance capabilities. Identifying satellite components can be beneficial for monitoring their operational status and health. Nevertheless, target orientation relative to the radar line of sight usually exhibits significant influences on the scattering mechanisms. Additionally, ISAR projection introduces orientational characteristics to satellite components in polarimetric ISAR images, which poses challenges for their precise localization and identification. Recently, this diversity in target scattering has been successfully characterized and employed using the three-dimension polarimetric correlation pattern (3-D PCP) interpretation technique, enabling the differentiation of various scattering structures. This study analyzes the relationship between satellite polarimetric responses and both polarimetric orientation angle and polarimetric ellipticity angle based on 3-D PCP. Then a hybrid approach combining 3-D PCP and data-driven model is designed for oriented satellite component recognition. In contrast to using a single polarimetric channel as input for deep neural networks, our approach transforms the data domain and utilizes three independent 3-D PCPs to drive the network. On one hand, the network training is guided by manually extracted features derived from 3D-PCP, including statistical characteristics such as mean, standard deviation, extreme values, and contrast. On the other hand, adaptive feature extraction is performed through a simple convolutional structure and integrated with electromagnetic scattering characteristics. Six satellites are utilized for constructing polarimetric ISAR dataset. Experimental results demonstrate that the proposed method achieves a superior performance, evidenced by a 2.3% improvement in the mean average precision (mAP) index.

This article proposes an adaptive infrared image detail enhancement algorithm guided by visual attention map for the issue that the output image of infrared detection equipment features concentrated gray value and low contrast. The algorithm separates the base layer and the detail layer via edge-preserving filters such as guided filtering, compresses the dynamic range of the base layer image, and adaptively enhances the detail layer image. Subsequently, the low contrast infrared image is reconstructed by the base layer after dynamic range compression and the detail layer after detail enhancement. Finally, the algorithm is deployed on the FPGA platform, which significantly improves the image contrast and meets the real-time requirements of the mid-wave infrared 640×512 array detection system.

Metalens is a novel optical element composed of sub-wavelength unit structure to achieve beam convergence imaging by modulating the electromagnetic wavefront, which has the advantages of lightweight, easy integration and rich functionality. To address the problem of poor imaging quality of long-wave infrared metalens, this paper proposes an infrared metalens image quality enhancement method based on the combination of point spread function extraction and non-blind restoration algorithm, and experimental validation is carried out, which effectively improves the imaging quality of long-wave infrared metalens.

The electron beam pumped excimer laser is a competitive candidate for inertial confinement fusion driver. In the excimer laser system, the diode serves as the core component, for its efficiency and reliability of the diode directly impact the laser's lifespan and electro-optical conversion efficiency. But there are no mature design standards for diodes, and many crucial designs rely on researchers' work experience. Particle-In-Cell Simulation is an efficient method to solve that problem. This article presents the mathematical and physical equations governing the transport of electron beams in the vacuum space of a diode, and discusses the application of Particle-in-Cell (PIC) simulation in the design of semiconductor laser diodes. It concludes that the use of PIC simulation allows for the calculation of the trajectory of electron beams, as well as the energy and angular distributions of the beams reaching the anode. Based on the simulation results, the diode can be optimized. It is found that efficient transportation of electrons to the anode surface can be achieved even without the use of guiding magnetic fields, though a drawback is the relatively large angle and dispersed energy distribution of the electron beams reaching the anode. The research offers insights for the efficient design of diodes.

The spot position detection technology based on the four-quadrant detector plays an important role in fields such as laser semi-active guidance, space laser communication, medicine, and precision measurement. The paper systematically summarizes the research progress of high-precision spot position detection technology based on the sum-and-difference algorithm model. First, the improved algorithm models under four conditions are discussed, namely the circular spot and uniform distribution, the circular spot and Gaussian distribution, the elliptical spot and uniform distribution, and the elliptical spot and Gaussian distribution. Further optimization algorithms based on these four models are also introduced. On this basis, although the detection accuracy has been significantly improved, there are still other factors that affect measurement accuracy in practical applications, such as inconsistent quadrant responsivity, noise, atmospheric turbulence, etc. These factors and their influencing trends or correction methods are classified and summarized. With the development of hardware processing capabilities, more new signal processing methods are being used to improve detection accuracy or precision, such as the digital lock-in amplifier method, the neural network method, the Kalman filtering method, etc. Some of these signal processing methods and their positive effects are introduced. Finally, prospects for future development are discussed.

The compound eye optical system has the characteristics of large field of view (FOV), high resolution, and strong environmental adaptability, which is an important technology that can break the mutual restraint between the field of view and spatial resolution in optical systems. Based on the characteristics of the compound eye system, we propose a multi-aperture imaging method in mid-wave infrared. The mid-wave fiber bundle array is used as a multi-aperture image plane splicing device, and the multiaperture image plane is coupled with the cooling detector using a secondary imaging structure. The experimental result shows that the optical detection system based on this technology can achieve an imaging distortion of less than 2% in arbitrary large FOV, and a uniform resolution of each large FOV angle, effectively achieving large FOV, small distortion and high-resolution imaging in mid-wave infrared imaging system.

Electron beam-pumped excimer lasers are capable of achieving high-power laser output in the extreme ultraviolet (EUV) wavelength range, with the advantage of a broad laser wavelength bandwidth and excellent beam uniformity, making them highly competitive candidate drivers for Inertial Confinement Fusion (ICF). Enhancing the energy deposition efficiency and lifetime of electron beam-pumped excimer lasers is of paramount importance for their application in ICF. This paper analyzes strategies to improve the energy deposition efficiency and lifespan of these lasers from two perspectives: pulsed power drivers and electron beam diodes. It summarizes the research advancements in this field and provides an overview of future research content and methodologies. The study presented herein aims to offer insights and guidance for the design of efficient and highly reliable electron beam-pumped excimer lasers.

In response to the needs of large-scale periodic data transmission tasks such as unmanned patrol video upload for forest fire prevention, traditional communication satellites are limited by uplink bandwidth and cannot meet their timeliness requirements. However, low-orbit broadband satellites have increasingly obvious application potential in the above scenarios due to their high-speed uplink characteristics. Taking the patrol video data upload of the core forest area of the Greater Khingan Range as an example, it is modeled as a regional time-division coverage problem within a fixed period, and a constellation configuration optimization and beam allocation algorithm based on particle swarm algorithm is proposed. The region is decomposed into many identical cells, and the time window and the number of beams are used as constraints. Considering the satellite power and the interference of adjacent beams, the particle swarm algorithm is used to optimize the constellation multi-beam allocation model. The simulation results show that under the same regional transmission period, the constellation configuration obtained by the proposed optimization algorithm uses fewer satellites, and can reduce the spatial interference of a single satellite beam, optimize beam allocation, effectively reduce mission costs, and improve resource utilization efficiency.

Addressing issues such as high-dimensional satellite telemetry data and data missing, the need for mass telemetry data for long-term training of payload action status monitoring models, and the limited scalability of existing monitoring method, this paper proposes a telemetry parameter model-oriented payload action patterns and a telemetry parameter comparison algorithm based on payload control plans. The proposed model utilizes principal component analysis (PCA) to identify key telemetry parameters specific to particular payload action patterns, significantly reducing data dimensionality and computational complexity. Additionally, the model generates simulated telemetry sequence to serve as a reference for evaluating actual telemetry parameter sequence. Building on these key telemetry parameters and the simulated sequence, the proposed algorithm processes the telemetry data by filling in missing values, removing null telemetry values, and standardizing the data. The algorithm then employs an improved entropy weight method to calculate the weights of telemetry parameters for payload action determination and compress the telemetry data, thereby reducing false alarm rate due to data supplement and lowering the computational load, to achieve the judgment of the execution of the satellite payload action. Validation using real telemetry data from a specific satellite model demonstrated a high accuracy of 87.5% in determining the execution status of satellite payload actions, surpassing the performance of direct sequence comparison post-preprocessing. This method provides ground-based operation control personnel with a reliable basis for assessing the operational status of satellite payloads.

Adaptive optics (AO) is widely used in the fields of ground-based telescopes, biological imaging, human eye aberration correction and laser communication to correct wavefront distortion. One of the key components of an AO system is a wavefront sensor (WFS). We demonstrate a 1×19 photonic lantern to be used as a single-aperture wavefront WFS. By detecting the power and the phase difference of 19 fundamental mode output at the single mode end of the photonic lantern, the lowest 19 order Zernike coefficients of the wavefront to be measured is determined. Simulation results show that when the wavefront distortion RMS< 1.5 π, the residual RMS between the reconstructed wavefront and the wavefront to be measured is always lower than 3.5 × 10⁻³ π, which provides a reliable technical means for realizing high-speed high accuracy and perfect common path wavefront sensing in AO system.

The near space holds significant importance for environmental protection, aerospace, and national defense. To address the challenges of detecting near space at altitudes above 60 km, this paper designs a rocket-based dropsonde system, innovatively employing high-dynamic temperature sensors and wide-range ultra-low pressure sensors to build an in-situ detection system for near space. To verify the feasibility of this system, a near-space detection experiment was conducted for altitudes above 60 km. The experimental results indicate that this system can successfully detect the near-space environment above 60 km. This experiment achieved the first domestic in-situ detection of near-space within the 20-70 km range, marking a pioneering effort in the detection of the near-space environment above 60 km in China.