Water-laser coupling is a critical aspect of water-jet guided laser processing, significantly affecting both the processing efficiency and quality. To further reduce the manufacturing costs, achieve uniform distribution of the water pressure inside the cavity and stability of the jet at low inlet pressures, and improve the performance of the coupling device and the quality of water-guided laser processing, a water-laser coupling device featuring multi-level symmetric channels was designed. The flow field distribution within the coupling device was analyzed, and the velocity vectors, the streamline distribution and the shape of the water jet were obtained. Simulation results show that the velocity vector distribution in each plane of the coupling device is stable without vortex, and the jet velocity at the nozzle outlet can reach 40 m/s, with a stable length of 120 mm. The results of experimental research reveal that the water jet from the nozzle is stable with an actual stable length of 85 mm, under the conditions of the water pressure of 1.0 MPa and the nozzle diameter of 250 m. The design of the coupling device is proven to be reasonable and meets the operational requirements of water-jet guided laser processing systems.

In order to expand the imaging depth of terahertz (THz) computed tomography (CT) system, 0.1 THz ultra long non diffractive beam was applied to continuous THz CT. A new type of faceted axicon was used to generate meter length non diffractive beam. A THz CT system for large-scale objects was built by using this non diffractive beam. With the support of the system, large-scale samples were scanned, and the projection data of the samples were obtained and reconstructed. The results show that, this new THz CT system can perform 3-D imaging of large-size samples with a diameter of 600 mm. And the internal 3-D structure of the object is obtained. This result provides an example for THz CT system for large-scale objects, and is helpful to expand the application scenarios of THz CT system.

A 13.5 nm extreme ultraviolet light source produced by the laser driven plasma is used in today's most advanced lithography machines and chip manufacturing. Generally, a 10.6 m CO2 gas laser is the driving light of commercial extreme ultraviolet lithography. In the future, solid-state lasers are expected to become a new generation of driving light sources due to their high plug efficiency and strong output power/energy scalability. The physical process of laser-plasma interaction for producing extreme ultraviolet light was summarized. The research progress of 10.6 m CO2 gas laser 1 m and 2 m solid-state lasers in driving plasma to produce extreme ultraviolet light and optical system was reviewed. The advantages of 1 m and 2 m solid-state lasers as driving light sources were emphatically discussed. On this basis, the research prospect of infrared laser driven extreme ultraviolet lithography source is prospected.

Synthetic aperture ladar can achieve high-resolution imaging with a small aperture, and had important application value in space-based space target observation. But, there were some problems such as narrow beam width, limited coverage, and difficult target search and acquisition. In order to solve these problems, a space-based synthetic aperture ladar space target imaging system combining active laser and passive infrared was adopted. The system index was analyzed, and the imaging simulation results were given. The results show that, the system is lightweight through laser/infrared common aperture. The problem of depolarization and target/platform vibration is solved by using circularly polarized laser emission signal and orthogonal linear polarization dual channel receiving signal, together with along orbital interference processing. Target search and tracking were realized through infrared camera. Target ranging and velocity measurement can be realized by using 10 ns pulse width narrow pulse laser signal. Pulse width and bandwidth of the optimized binary phase shift keying coded laser signal were 10 ns and 4 GHz. 0.10 m real-time low resolution imaging and 0.05 m high resolution imaging can be achieved. The system design scheme has reference value for the development of space-borne synthetic aperture ladar.

Silicon single-photon avalanche photodiodes have become one of the most promising single-photon detectors for space applications due to their performance advantages, such as low dark count rate and high single-photon detection efficiency, as well as their technical features like miniaturization and no need for ultra-low cooling temperatures. The key technology is to reduce the damage caused by space radiation environment, reduce the dark count rate and extend the service life of the detector. The research status and trend of silicon single-photon avalanche photodiode in anti-irradiation technology were introduced, the working mechanism of single-photon detectors and the influence of spatial radiation effects on detector performance were described, and the future development prospect of silicon single-photon avalanche photodiode was prospected. It is pointed out that by enhancing the application of four anti-radiation methods, including cooling, thermal annealing, laser annealing, and structural optimization, the performance and reliability of the detector are expected to be further improved, and effective technical support is provided for the development of space exploration and space-ground communication.

Most Fabry-Prot (F-P) interferometers that with a gas-gap F-P cavity structure are usually limited by mirror adjustment, stability, and volume limitations. To address these limitations, a solid-gap F-P cavity structure was proposed. A simulation of the solid-gap F-P interferometer was conducted using the theory of multi-beam interference to determine the peak position of each level of interference fringe and the half-height full-width position. The impact of three factors on the imaging quality of the solid-gap F-P interferometer was analyzed, which were cavity length, reflectivity and refractive index of the solid-gap F-P cavity. And a 16 mm thick solid-gap F-P cavity sample was processed according to the requirements. In comparing the actual detection with the theoretical simulation, it was found that the deviation of the peak position of the first level fringe is better than 5 pixels, and the deviation of the other levels of fringe is better than 2 pixels. The two are in good agreement. This work validates the applicability and scalability of the solid-gap structure in interferometer imaging, completes the basic theoretical exploration of the solid-gap F-P interferometer, and provides a reference for relevant research and development.

In order to solve the one-sidedness and limitations of chemical purification methods, the fluorescence spectrum of Gastrodia elata powder with multiple components was theoretically analyzed and experimentally verified by combining trilinear decomposition algorithm, sum of squared error method, split-half method, and synchronous fluorescence spectroscopy. And it is demonstrated that the algorithm model for fluorescence of Gastrodia elata powder solution has three components. The results show that the first component has a characteristic fluorescence peak at excitation wavelengths of ex=275 nm~280 nm, emission wavelengths of em=305 nm~310 nm, and the fluorescent material corresponding to this component should be gastrodin, which has a high content in Gastrodia elata; the second component has a characteristic fluorescence peak at excitation wavelengths of ex=305 nm~310 nm, emission wavelengths of em=400 nm~405 nm; and the third component has a fluorescence peak at excitation wavelengths of ex=355 nm~360 nm, emission wavelengths of em=440 nm~445 nm; the complicated chemical separation can be replaced by the trilinear decomposition algorithm of mathematical separation, furthermore, it has the advantages of removing background noise interference, simplifying high-dimensional spectral analysis, and expressing the fluorescence characteristics of multi-component coexisting substances from an overall perspective and global features. This research provides a reference for the spectral analysis of multi-component substances.

In order to improve the performance of integer-pixel displacement search algorithm of digital image correlation (DIC) method, the white shark optimizer was introduced and improved by adopting tent mapping, introducing dynamic nonlinear time factor, setting automatic termination condition and adding three-step search method. In order to improve the accuracy and efficiency of sub-pixel displacement solving, an improved surface fitting method was proposed by combining bicubic interpolation, and the white shark optimizer and surface fitting method was improved. The performance of the two algorithms was tested by numerical simulation experiments and tensile experiment of low-carbon steel. The experimental results exposes that, the improved white shark optimizer has a search success rate of up to 100%, with a computational time comparable to that of the particle swarm optimization and only a quarter of that of the coarse-fine search method. The computational accuracy of the improved surface fitting method is comparable to that of the Newton-Raphson (N-R) algorithm, but the computational time consumed is only 3.50% of the N-R algorithm. The improved white shark optimizer can achieve integer-pixel displacement search quickly and accurately. The improved surface fitting method has high computational accuracy and efficiency, and still maintains good stability in actual measurements. This study provides a reference for the improvement and application of digital image correlation method.

To enhance the thermal efficiency and reduce surface defects in magnesium alloy welding, a power-modulated oscillation laser welding technique was proposed. Butt welding was performed on 5 mm thick AZ31B magnesium alloy, and the surface formation, microstructure, and mechanical properties of the weld were analyzed. Additionally, numerical simulation and simulation analysis of the welding temperature field were conducted. The results indicate that compared to the effects of conventional laser welding, welding defects decrease significantly, weld width increases, and energy coupling efficiency is improved with power-modulated oscillation laser welding. The grains in the center of the weld are refined, and the formation of -strengthening phases increase, leading to enhanced mechanical properties, with the ultimate tensile strength and elongation reaching 96.1% and 58.7% of the base material, respectively. The temperature at the center of the weld is reduced by approximately 500 K, resulting in a more uniform heat distribution and a decreased temperature gradient in the melt pool. These findings have significant practical implications for improving the performance of magnesium alloy joints, lightweight transportation, and energy conservation and emission reduction.

In order to process the blade air film holes with small aperture, small taper, no recast layer, micro-cracks and other defects, a femtosecond helical drilling platform was built to carry out the hole drilling test. The working principle of helical drilling optical system was analyzed. The effects of wedge prism deflection angle, mirror translation, hollow motor speed, laser power, and defocusing amount on aperture, taper, splash, and color region of microholes were studied by orthogonal test and variance analysis. It was concluded that in helical drilling the deflection angle of the wedge prism have the most significant effect on the hole diameter and the translation of the reflector had the most significant effect on the taper. The optimized parameters for processing 400 m cylindrical hole are deflection of the wedge prism 15°, translation of the reflector 15 mm, the hollow motor 2000 r/min, power 16 W, and defocusing 0.2 mm, respectively. This study provides a reference for the selection of parameters in femtosecond helical drilling.

In practical environment, severe interference can be observed in the extraction of rotational Doppler signals due to atmospheric turbulence and non-ideal targets. In order to retrieve effective Doppler signals amidst such interference, a method of polarization measurement employing higher-order vector vortex beams was employed. Subsequently, a rotational Doppler measurement system with resistance to turbulence, founded on vector vortex beams, was established, enabling the determination of rotational Doppler shifts under varying turbulence intensities. Doppler signals for rough targets moving at diverse velocities were obtained successfully. Experimental findings suggest that, the measurement of two angular velocities under different turbulence intensities using the 5th, the 10th, the 15th, and the 20th order vortex beams validates that within intricate environments. Turbulence noise can be substantially filtered out through the utilization of the polarization dimension. Thus, the accurate measurement of the angular velocities of objects can be realized. Furthermore, higher-order vortex beams are more advantageous in enhancing the robustness of the measurement system in complex environments. This study offers invaluable references for data monitoring in turbulent environments across a spectrum of disciplines, encompassing wind power generation, weather forecasting, medical research, and marine and atmospheric sciences.

In order to improve the trapping efficiency of the double-tapered optical fiber probe (DOFP), the first taper angle was fabricated by the static chemical etching method, and then the second taper angle was fabricated by the polishing method. Trapping experiment of a yeast cell was completed using a single optical fiber tweezer system based on DOFP. In addition, a DOFP with similar parameters was fabricated by interfacial layer etching method. The trapping force of two DOFPs fabricated by two different methods on the yeast cell was measured. The results show that, DOFP fabricated by the hybrid method has better surface smoothness and symmetry. Its trapping efficiency is 20% higher than that of DOFP fabricated by the interfacial layer etching method. This study is helpful for the fabrication of double-tapered optical fiber probes using the hybrid method.

Matrix effect was a technical limitation for the development of laser-induced breakdown spectroscopy (LIBS). To reduce the matrix effect and address the challenges in preparing standard complex matrix samples, standard addition method was introduced into the field of LIBS. Five implementation methods of standard addition method were introduced. The specific applications such as environmental monitoring, archaeology, mineral detection, food, and medicinal safety monitoring were summarized. The principles and applications of three improved methods: Online standard addition method, data processing assisted standard addition method, and sample simplification standard addition method were discussed. Online standard addition method can achieve the automated sample preparation and improve the efficiency of LIBS technology quantitative analysis. Data processing assisted standard addition method weakens spectral background interference, spectral fluctuations, and self-absorption effects, and improves the quantitative analysis accuracy of LIBS technology assisted by the standard addition method. Sample simplification standard addition method overcomes the disadvantage of not being able to directly detect powder samples, and improves the detection efficiency of LIBS technology assisted by standard addition method while simplifying the sample quantity. The progress in these applications and improvement methods indicate that standard addition method-LIBS has the advantages in the trace detection of liquid and powder samples.

In order to solve the problems of large volume and complex structure of traditional aerosol light detection and ranging (LiDAR), a compact portable micro pulse LiDAR system was proposed. The aspheric lens optical transceiver system was designed by using the optical structure of coaxial transceiver. The stray light was analyzed, and the influence of stray light was reduced through the structural design. Theoretical analysis and experimental verification were carried out, and aerosol detection data after reducing the influence of stray light were obtained. The results show that, the range resolution of the developed radar system is 6 m, and the aerosol distribution within 3 km can be detected in real time. This study provides a reference for the miniaturization of micro pulse LiDAR equipment.

In order to improve detection range and environmental adaptability of a toxicant light detection and ranging (LiDAR), a long-wave receiving optical system with refractive-diffractive structure was designed by using passive athermalization. By utilizing unique chromatic aberration characteristics of a binary diffraction surface, the chromatic aberration and secondary spectrum of optical system were corrected. Under the condition that the working wavelength was from 9 m to 11 m, focal length was 270 mm, F number was 2.27, and optical efficiency was higher than 86.6%, tolerance analysis was conducted with Monte Carlo statistical method. By conducting temperature and flight tests to measure the key technical indicators, the simulation results and design rationality were verified. The results show that the wavefront root mean square of optical system is 0.03, and the modulation transfer function is higher than 0.47 in the temperature range of -40 ℃~60 ℃, so the image quality is excellent. In flight test, the maximum detection distance of toxicant LiDAR that applies this optical system reaches 4.05 km. The result is superior to system requirements, so the designed optical system is qualified. The study provides positive effects on development of laser active telemetry radar for biochemical environment.

In order to further study the effect of laser incidence angle on the surface cleaning of non-uniform coating, different inclined incidence angles of 90°, 75°, 60°, 45° and 30° were selected to carry out laser cleaning experiments on the non-uniform thickness of 6061 aluminum alloy. Surface morphology, roughness and hardness after treatment were measured, and a laser thermal effect model was constructed. The effect of laser on the surface temperature distribution and morphology of aluminum alloy matrix at different incidence angles was revealed by comparison between simulation and experimental results. The results show that, different incidence angles have significant effects on the removal of non-uniform paint layer and the damage degree of aluminum surface during laser cleaning. The surface roughness value of laser cleaning at 30° incidence angle is reduced by nearly 22 m, or 80%, compared with the 90° vertical incidence laser. With the increase of the incidence angle, Vickers hardness after cleaning is gradually increased. The oblique incidence laser cleaning method has better effect on the treatment of uneven surface coating, and can significantly improve the surface smoothness. This study not only provides a valuable reference for the optimization of laser cleaning technology, but also contributes practical scientific data for the development of non-uniform coating surface treatment technology.

In order to fill the research gap in the field of external parameter calibration between the camera and the angle of arrival (AoA) base station, the checkerboard calibration board was used to extract the label position from the image, and the optimal external parameter was calculated based on the geometric constraint between the two sensor data. Theoretical analysis and experimental verification were carried out, and the simulation and experimental data were obtained. The results show that, the distance error of the calibration results obtained by this method is within 0.08 m, and the angle error is within 3.5°. The research is helpful for the calibration of external parameters between camera and AoA base station and the design of robot sensing system.

Lhasa Gonggar Airport is located in the Yarlung Zangbo River Valley. Due to the combined effects of topography and underlying surface, the wind field environment here is complex. In order to verify the wind field detection capability of wind light detection and ranging (LiDAR) on the high plateau and summarize the experience of wind change forecast, FC-Ⅲ wind LiDAR was used. Combined with aircraft air reports and ground observation data, the wind shear monitoring capability and wind change process LiDAR product characteristics were analyzed. The results show that the high temporal and spatial density monitoring capability of wind LiDAR can better capture the wind shear on the approach route within a range of 4000 m; can The conduction of the mid-level outflow ranging from 1000 m to 2000 m and the advancement of the near-ground strong wind area which below 1000 m caused by convective clouds in advance can be tracked by the LiDAR product of the wind change process in the rainy season. The refined wind change time of the runway based on factors such as maximum wind speed and distance were further calculated; during the dry season, the triggering height of southerly component is 1000 m to 1500 m, there are characteristics such as mid-level momentum loss, vertical airflow and divergence mutation after ground wind turning, 20 min before turning to the west wind, the westerly component ranging from 1000 m to 2000 m has increased to more than 10 m/s, the middle-level and high-level westerly component are maintained after ground wind turning, and the relationship between the inflow area advancement position and the wind transition node can be statistically analyzed as an accumulation index for refined forecasting. This study has important reference value for broadening the application scenarios of wind LiDAR in high plateaus and improving the level of refined ground wind forecasting.

In order to engineering the 800 nm lasers used as the light source of laser illumination in wide-temperature range, an end-face pumped solid laser was used in the experiments. The output 1064 nm laser beam of the diode array end-face pumped Nd∶YAG laserpassed through a KTiOPO4 (KTP) crystal, then 532 nm laser was obtained from frequency doubling of 1064 nm. Finally, the output 800 nm laser was realized after the process of optical parametric oscillator using 532 nm laser works as pump source. Active temperature controlling and multi-wavelength matching was used for laser diode array. Active heating was used for KTP. The experiment results show that the 800 nm lasers is realized with energy over 20 mJ, pulse width 12 ns and divergence angle 3.5 mrad; It can work over 3 min in 25 Hz in wide-temperature range -40 ℃~55 ℃; The output laser of this design has higher peak power, better laser beam quality and narrower pulse width compared with directly using 808 nm semiconductor laser as the light source, and these advantages are conducive to increase the working distance of laser illumination and accuracy. The temperature adaptability of this laser is high when it is worked as the light source of the active laser illumination imaging. So it can meet the demand of engineering, especially the demand of the wide using temperature.

To effectively address the issue of spectrum fragmentation resulting from resource allocation in space division multiplexing elastic optical networks (SDM-EON) of multi-core fiber, a load resource synergy temporal-spatio-frequency (LRS-TSF) fragmentation perception algorithm was proposed. Firstly, a routing selection strategy was designed by considering the path load and service frequency slot requirements, prioritizing paths with lower path load and fewer service frequency slot demands. Then, a 3-D measurement of available spectrum resources was conducted from the perspective of time, space, and frequency, introducing a TSF fragmentation perception model to avoid spectrum fragmentation during the service allocation process and reserve contiguous idle spectrum resources for subsequent services. Simulation results demonstrate that when the load ranges from 400 Erlang to 960 Erlang, the LRS-TSF algorithm achieves better performance in terms of blocking probability, spectrum utilization, and fragmentation rate compared to other algorithms. The study provides a reference for further addressing the issue of spectrum fragmentation in elastic optical networks with spatial division multiplexing.

In order to improve the stable length of small-scale water jets, relevant software and two-phase fluid volume model were used. By setting relevant parameters, a diameter of 60 m~100 m of water jet was simulated on computational fluid dynamics. The effective length of water jet in different scenarios was studied. A new type of nozzle structure for actively generating a gas protective layer was designed. The results indicate that, when the nozzle diameter is 100 m, the pressure is below 30 MPa, the traditional method of forming a contracted water jet with sharp right angles is not feasible due to the influence of machining accuracy. A relatively stable water jet at a pressure of 0.7 MPa can be generated. This method has low processing difficulty and requires low pressure, which has the reference value for the design and manufacturing of nozzle structures in water guided laser processing.

In order to achieve the goal of high-precision detection of specific target areas, a 1064 nm laser 3-D imaging experimental system was constructed based on a self-developed 32×32 silicon Geiger-mode laser focal plane detector by utilizing the staring laser 3-D imaging technology. Sterling cryogenic packaging technology with a temperature sampling and control module was employed in the detector, which enabled high-precision temperature control and stable operation in a deep cryogenic environment. For the imaging system, the target area with a pulsed laser dot array was illuminated, and the aforementioned detector was used to capture the laser echo signal. After distance gate noise filtering and 3-D point cloud data preprocessing, a 3-D range image of a target at 200 m and a 2-D intensity image of a target at 670 m were successfully obtained. The results demonstrate that the laser 3-D imaging system has a distance resolution of 30 cm, capable of accurately depicting the geometric details of the target. This study provides a reference for the practical engineering application of the staring 3-D imaging technology based on silicon Geiger-mode laser focal plane detector.

In order to improve the classification and recycling efficiency of electronic waste, a detection and identification system of electronic phosphor based on laser-induced breakdown spectroscopy and principal components analysis (PCA) algorithm & back propagation (BP) algorithm was established. In order to verify the reliability of the system, three different models of phosphor (CRT-B, P43 and P47) were taken as examples. The system was used to obtain the laser-induced breakdown spectral data of phosphor samples in the range of 200 nm~890 nm, and the spectral line calibration and element calibration were completed. The results showe that the phosphor CRT-B is rich in Zn and Al, P43 is rich in Gd, P47 is rich in Y and Si, and trace element Ce is also detected in the phosphor P47. The results show that the contribution rate of the first three principal components is as high as 99.769%, and the three phosphors can be clearly separated in space. The recognition rates of CRT-B, P43 and P47 phosphor by PCA-BP are 99.8%, 100% and 100%, respectively. The results of this study are helpful for the rapid detection and recycling of electronic waste in industrial production and life.