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RSS2022 Vol. 46, No. 5
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2022, 46(5): 579-584.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.001
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Abstract:
In order to clarify the influence of the spontaneous radiation of different-shape shields on detectors and find out the shape that has the least impact, the spontaneous power to the detector from the inner shields with different shapes was systematically analyzed by theoretical calculation. The shapes of the shields include paraboloid, hyperboloid, semi-ellipsoid (including hemisphere), and frustum of cone (including cylinder and cone). The results showed that the spontaneous power to the detector of all shapes of shields first decreases and then increase with the increase of the ratio of the height of the shield to the radius of the bottom. The maximum radiation power is a constant related to the size of the detector, and the minima appear when the heights of the shields are close to or equal to the radiuses of the bottoms. When the shield is semi-ellipsoidal and the height is equal to the radius (i.e., hemisphere), the power of spontaneous radiation to the detector is less than that of any other shield, and it has nothing to do with the size of the shield or whether there are small holes on the top. This study can provide a valuable reference for the design of radiation shields.
In order to clarify the influence of the spontaneous radiation of different-shape shields on detectors and find out the shape that has the least impact, the spontaneous power to the detector from the inner shields with different shapes was systematically analyzed by theoretical calculation. The shapes of the shields include paraboloid, hyperboloid, semi-ellipsoid (including hemisphere), and frustum of cone (including cylinder and cone). The results showed that the spontaneous power to the detector of all shapes of shields first decreases and then increase with the increase of the ratio of the height of the shield to the radius of the bottom. The maximum radiation power is a constant related to the size of the detector, and the minima appear when the heights of the shields are close to or equal to the radiuses of the bottoms. When the shield is semi-ellipsoidal and the height is equal to the radius (i.e., hemisphere), the power of spontaneous radiation to the detector is less than that of any other shield, and it has nothing to do with the size of the shield or whether there are small holes on the top. This study can provide a valuable reference for the design of radiation shields.
2022, 46(5): 585-593.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.002
Abstract:
Diode pumped alkali laser (DPAL) have been rapidly developed because of their high Stokes efficiency, good beam quality, compact size, and near-infrared emission wavelengths. As typical three-level lasers, the DPAL can be irradiated at the wavelengths of 895nm (Cs), 795nm (Ru), and 770nm (K), respectively. The laser kinetics and important research development are concluded in this paper, and the theoretical and experimental studies of our group are also introduced. Then, some problems and difficulties in this field have been discussed. Finally, we analyzed the development trend of DPAL in the near future.
Diode pumped alkali laser (DPAL) have been rapidly developed because of their high Stokes efficiency, good beam quality, compact size, and near-infrared emission wavelengths. As typical three-level lasers, the DPAL can be irradiated at the wavelengths of 895nm (Cs), 795nm (Ru), and 770nm (K), respectively. The laser kinetics and important research development are concluded in this paper, and the theoretical and experimental studies of our group are also introduced. Then, some problems and difficulties in this field have been discussed. Finally, we analyzed the development trend of DPAL in the near future.
2022, 46(5): 594-600.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.003
Abstract:
In order to obtain a new elliptically twisted multi-Gaussian-Schell model beam, a Mercer model expansion method was adopted, the theoretical analysis and verification were carried out. It is proved that the twisted phase can be carried in the multi-Gaussian-Shell model correlation structure, and the intensity and coherence evolution of the beam propagating in gradient index fibers was studied. The results show that when elliptically twisted multi-Gaussian-Schell model beams are propagating in the graded index fibers, the distribution of intensity and coherence rotates periodically with the increase of transmission distance, and the deflection is π/2 degrees at the integer multiples of 0.5L (L is a cycle). The rotation angular velocity is nonlinear and related to the size of the twist factor. With the increase of multi-Gaussian modulus, the flat top region of the intensity distribution at the focal plane increases, and the coherence distribution contour becomes smaller. The research results have potential applications in optical fiber communication, focused imaging, optical capture and so on.
In order to obtain a new elliptically twisted multi-Gaussian-Schell model beam, a Mercer model expansion method was adopted, the theoretical analysis and verification were carried out. It is proved that the twisted phase can be carried in the multi-Gaussian-Shell model correlation structure, and the intensity and coherence evolution of the beam propagating in gradient index fibers was studied. The results show that when elliptically twisted multi-Gaussian-Schell model beams are propagating in the graded index fibers, the distribution of intensity and coherence rotates periodically with the increase of transmission distance, and the deflection is π/2 degrees at the integer multiples of 0.5L (L is a cycle). The rotation angular velocity is nonlinear and related to the size of the twist factor. With the increase of multi-Gaussian modulus, the flat top region of the intensity distribution at the focal plane increases, and the coherence distribution contour becomes smaller. The research results have potential applications in optical fiber communication, focused imaging, optical capture and so on.
2022, 46(5): 601-609.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.004
Abstract:
Single-photon detector can detect very weak light with high sensitivity, which has been widely used in the field of civil and national defense. With the development of technology, in addition to the optimization and improvement of traditional photodetectors, other new photodetectors have also been greatly developed and important technical achievements have been made. In order to deeply understand the development status and trend of single-photon detectors, the key information in research status, technical difficulties, and latest technological breakthroughs of representative single-photon detectors were summarized. The advantages and disadvantages of traditional single-photon detectors such as photomultiplier tube and avalanche photodiode were analyzed as well as the future technical development direction. At the same time, the superconducting nanowire single-photon detectors and avalanche photodiode based on new 2-D materials with good photoperformance and great development potential were introduced. And the future direction was prospected.
Single-photon detector can detect very weak light with high sensitivity, which has been widely used in the field of civil and national defense. With the development of technology, in addition to the optimization and improvement of traditional photodetectors, other new photodetectors have also been greatly developed and important technical achievements have been made. In order to deeply understand the development status and trend of single-photon detectors, the key information in research status, technical difficulties, and latest technological breakthroughs of representative single-photon detectors were summarized. The advantages and disadvantages of traditional single-photon detectors such as photomultiplier tube and avalanche photodiode were analyzed as well as the future technical development direction. At the same time, the superconducting nanowire single-photon detectors and avalanche photodiode based on new 2-D materials with good photoperformance and great development potential were introduced. And the future direction was prospected.
2022, 46(5): 610-617.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.005
Abstract:
For better detection of low-level wind shear, a new algorithm based on the wavelet transform modulus maxima methodI was introduced to predict the occurrence of wind shear along the glide path. Wavelet transform is used to obtain the modulus maximum value on the recombined upwind profile. The "inflection point" was found, and then the windshear judgment standard was used to judge its accuracy. Numerical examples and field detection data from Yunxi Meteorological Station in Hubei Province and Panzhihua Airport in Sichuan Province have well verified the good performance of the method, in terms of both accuracy and efficiency. The result shows that the pulse-type data is more accurate using the even number wavelet in the biorthogonal system; the step-type and ramp-type data is more accurate using the Db5 in the Daubechies system. The results show that the wind shear occurred in Yunxi county and Panzhihua Baoanying Airport, the wind shear intensity were both heavy. This algorithm can detect different types of wind shear without considering the scale of wind shear, which makes up for the shortcomings of existing algorithms, provides technical support for aircraft takeoff and landing, and has great significance for real-time detection and early warning.
For better detection of low-level wind shear, a new algorithm based on the wavelet transform modulus maxima methodI was introduced to predict the occurrence of wind shear along the glide path. Wavelet transform is used to obtain the modulus maximum value on the recombined upwind profile. The "inflection point" was found, and then the windshear judgment standard was used to judge its accuracy. Numerical examples and field detection data from Yunxi Meteorological Station in Hubei Province and Panzhihua Airport in Sichuan Province have well verified the good performance of the method, in terms of both accuracy and efficiency. The result shows that the pulse-type data is more accurate using the even number wavelet in the biorthogonal system; the step-type and ramp-type data is more accurate using the Db5 in the Daubechies system. The results show that the wind shear occurred in Yunxi county and Panzhihua Baoanying Airport, the wind shear intensity were both heavy. This algorithm can detect different types of wind shear without considering the scale of wind shear, which makes up for the shortcomings of existing algorithms, provides technical support for aircraft takeoff and landing, and has great significance for real-time detection and early warning.
2022, 46(5): 618-623.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.006
Abstract:
In order to achieve the simultaneous measurement and sensing detection of temperature and solution mass fraction in the industrial production process, a new dual-parameter sensor, which was composed of Fabry-Perot interference (FPI) and Mach-Zehnder interference (MZI) cascading interference structure was proposed. This new type of dual-parameter sensor cascade structure was composed of a single mode fiber (SMF) and a hollow core fiber (HCF) fused together. A method of simultaneously measuring the characteristic wavelength shift of the FPI reflection spectrum and the MZI transmission spectrum was adopted, and then the sensitivity difference between FPI and MZI to temperature and refractive index was obtained. The measurement of dual parameters of the sensor was realized by establishing the sensor temperature-mass fraction sensitivity matrix. The results show that the temperature sensitivity of FPI is 10pm/℃ in the temperature range of 40℃~150℃, while MZI is not sensitive to temperature. In the range of mass fraction 0.05~0.40, FPI is not sensitive to refractive index, while the sensitivity of MZI mass fraction is 232.3nm/RIU. The temperature and solution mass fraction can be measured by using this sensor. The study provides a reference for the dynamic measurement of dual-parameter in the processing industries such as petroleum, chemical, electricity, steel, and machinery.
In order to achieve the simultaneous measurement and sensing detection of temperature and solution mass fraction in the industrial production process, a new dual-parameter sensor, which was composed of Fabry-Perot interference (FPI) and Mach-Zehnder interference (MZI) cascading interference structure was proposed. This new type of dual-parameter sensor cascade structure was composed of a single mode fiber (SMF) and a hollow core fiber (HCF) fused together. A method of simultaneously measuring the characteristic wavelength shift of the FPI reflection spectrum and the MZI transmission spectrum was adopted, and then the sensitivity difference between FPI and MZI to temperature and refractive index was obtained. The measurement of dual parameters of the sensor was realized by establishing the sensor temperature-mass fraction sensitivity matrix. The results show that the temperature sensitivity of FPI is 10pm/℃ in the temperature range of 40℃~150℃, while MZI is not sensitive to temperature. In the range of mass fraction 0.05~0.40, FPI is not sensitive to refractive index, while the sensitivity of MZI mass fraction is 232.3nm/RIU. The temperature and solution mass fraction can be measured by using this sensor. The study provides a reference for the dynamic measurement of dual-parameter in the processing industries such as petroleum, chemical, electricity, steel, and machinery.
2022, 46(5): 624-629.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.007
Abstract:
In order to improve the accuracy of road unevenness detection by vehicle-mounted lidar in outdoor scenes, the road environment information was extracted and segmented by the network structure of random down-sampling and local feature aggregation. Random sampling method was added in the segmentation process to improve the computing efficiency of high point cloud information. To solve the problem of the loss of key features in the segmentation process of road environment information, local feature aggregator was added to increase the acceptance domain of each 3-D point cloud to retain geometric details. The results show that the proposed algorithm can accurately identify the road environment information, and the recognition accuracy of convex hull, pit, and road able area reaches 71.87%, 82.71%, and 93.01% respectively, which is significantly improved compared with the traditional convolution neural network. This study can efficiently extract the information of road roughness and road able area. Thus, the active safety and ride comfort of the vehicle are improved.
In order to improve the accuracy of road unevenness detection by vehicle-mounted lidar in outdoor scenes, the road environment information was extracted and segmented by the network structure of random down-sampling and local feature aggregation. Random sampling method was added in the segmentation process to improve the computing efficiency of high point cloud information. To solve the problem of the loss of key features in the segmentation process of road environment information, local feature aggregator was added to increase the acceptance domain of each 3-D point cloud to retain geometric details. The results show that the proposed algorithm can accurately identify the road environment information, and the recognition accuracy of convex hull, pit, and road able area reaches 71.87%, 82.71%, and 93.01% respectively, which is significantly improved compared with the traditional convolution neural network. This study can efficiently extract the information of road roughness and road able area. Thus, the active safety and ride comfort of the vehicle are improved.
2022, 46(5): 630-635.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.008
Abstract:
In order to study the high quality factor Q based on the bound state in the continuum (BIC), a terahertz all-dielectric metasurface composed of double hollow silicon cylinders was proposed. The transmission spectrum and electromagnetic field diagrams of the structure were simulated and analyzed. The eigenmode analysis was used to study the influence of the metasurface structure parameters on the BIC frequency, and a BIC metasurface working in a large terahertz frequency range was desigined. The results show that an adjustable high-Q toroidal dipole Fano resonance is realized at around 3.0THz. The results of symmetry mismatch between the eigenmode analysis calculation and the incident electromagnetic wave mode. The analysis indicate that the metasurface supports a symmetry-protected BIC. This research provides a theoretical reference for the application of high-Q metamaterials based on BIC in the fields of ultra-low threshold laser devices, nonlinear optical harmonic generation, and high-sensitivity sensing.
In order to study the high quality factor Q based on the bound state in the continuum (BIC), a terahertz all-dielectric metasurface composed of double hollow silicon cylinders was proposed. The transmission spectrum and electromagnetic field diagrams of the structure were simulated and analyzed. The eigenmode analysis was used to study the influence of the metasurface structure parameters on the BIC frequency, and a BIC metasurface working in a large terahertz frequency range was desigined. The results show that an adjustable high-Q toroidal dipole Fano resonance is realized at around 3.0THz. The results of symmetry mismatch between the eigenmode analysis calculation and the incident electromagnetic wave mode. The analysis indicate that the metasurface supports a symmetry-protected BIC. This research provides a theoretical reference for the application of high-Q metamaterials based on BIC in the fields of ultra-low threshold laser devices, nonlinear optical harmonic generation, and high-sensitivity sensing.
2022, 46(5): 636-640.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.009
Abstract:
In order to obtain high quality steel/aluminum joints, the lapping experiments of DP780 duplex steel and 5083 aluminum alloy with different power were carried out by laser swing welding. The effects of different welding power on the macroscopic morphology, microstructure, and mechanical properties of steel/aluminum joints were investigated. The test results show that the plate welding can be effectively realized within the power range of 1400W~1600W. When the laser power is 1400W and 1500W, the metallographic structure of the welded joint is dominated by martensite. When the laser power is 1600W, the amount of ferrite in the joint increases, while the martensite decreases, and the metallographic structure of the welded joint is dominated by ferrite. The lowest and highest microhardness of the three joints were located in the weld zone and the heat affected zone, respectively. Under the laser power of 1500W, the mechanical properties of the welded joint are the best, and the microhardness of the steel side joint is about 1.7 times higher than that of the base metal. The maximum shear strength of the joint is 113N/mm. The research results are of great significance in the field of shipbuilding.
In order to obtain high quality steel/aluminum joints, the lapping experiments of DP780 duplex steel and 5083 aluminum alloy with different power were carried out by laser swing welding. The effects of different welding power on the macroscopic morphology, microstructure, and mechanical properties of steel/aluminum joints were investigated. The test results show that the plate welding can be effectively realized within the power range of 1400W~1600W. When the laser power is 1400W and 1500W, the metallographic structure of the welded joint is dominated by martensite. When the laser power is 1600W, the amount of ferrite in the joint increases, while the martensite decreases, and the metallographic structure of the welded joint is dominated by ferrite. The lowest and highest microhardness of the three joints were located in the weld zone and the heat affected zone, respectively. Under the laser power of 1500W, the mechanical properties of the welded joint are the best, and the microhardness of the steel side joint is about 1.7 times higher than that of the base metal. The maximum shear strength of the joint is 113N/mm. The research results are of great significance in the field of shipbuilding.
2022, 46(5): 641-647.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.010
Abstract:
In order to monitor the pressure and temperature changes in petrochemical reactor under high temperature and high pressure in real time and strictly control the reaction process of raw materials, an optical fiber Fabry-Perot (F-P) temperature and pressure composite sensor was designed and fabricated by using F-P multi cavity interference theory. The sensor was composed of quartz glass and sapphire glass. The air chamber between quartz and sapphire was pressure chamber, and the temperature chamber was sapphire itself. Through theoretical calculation and simulation verification, the effects of different parameters of pressure chamber and temperature chamber on the performance of the sensor were analyzed, and the best structural parameter data of the sensor were obtained. The results show that the sensor has simple fabrication process and reliable performance, and can realize the simultaneous measurement of pressure and temperature in the range of 0MPa~5MPa and -20℃~300℃. The experimental results show that the sensor has a good linear response relationship between pressure and temperature under the environment of pressure 0.1MPa~5MPa and temperature 20℃~180℃. The pressure sensitivity is 796nm/MPa and the temperature sensitivity is 3.864nm/℃. The sensor is suitable for simultaneous monitoring of pressure and temperature in high temperature and high pressure environment in petrochemical reactor.
In order to monitor the pressure and temperature changes in petrochemical reactor under high temperature and high pressure in real time and strictly control the reaction process of raw materials, an optical fiber Fabry-Perot (F-P) temperature and pressure composite sensor was designed and fabricated by using F-P multi cavity interference theory. The sensor was composed of quartz glass and sapphire glass. The air chamber between quartz and sapphire was pressure chamber, and the temperature chamber was sapphire itself. Through theoretical calculation and simulation verification, the effects of different parameters of pressure chamber and temperature chamber on the performance of the sensor were analyzed, and the best structural parameter data of the sensor were obtained. The results show that the sensor has simple fabrication process and reliable performance, and can realize the simultaneous measurement of pressure and temperature in the range of 0MPa~5MPa and -20℃~300℃. The experimental results show that the sensor has a good linear response relationship between pressure and temperature under the environment of pressure 0.1MPa~5MPa and temperature 20℃~180℃. The pressure sensitivity is 796nm/MPa and the temperature sensitivity is 3.864nm/℃. The sensor is suitable for simultaneous monitoring of pressure and temperature in high temperature and high pressure environment in petrochemical reactor.
2022, 46(5): 648-652.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.011
Abstract:
In order to satisfy the laser cleaning application for a variety of materials insulators, a self-developed pulsed master oscillator power amplifier (MOPA) fiber laser with a laser energy of 2mJ was adopted. The cleaning of the glass insulator, porcelain insulator, and silicon rubber insulator had been effectively finished by a MOPA laser in this work. Also, the relationships between the cleaning speed, pulsed laser parameters, and cleaning effect of the insulator were analyzed. At the highest laser scanning speed of 10m/s, the cleaning efficiency of 3.4cm2/s could be reached, and the optimized laser parameters of insulators with different materials were studied for provision of reference in electrical insulators laser cleaning application.
In order to satisfy the laser cleaning application for a variety of materials insulators, a self-developed pulsed master oscillator power amplifier (MOPA) fiber laser with a laser energy of 2mJ was adopted. The cleaning of the glass insulator, porcelain insulator, and silicon rubber insulator had been effectively finished by a MOPA laser in this work. Also, the relationships between the cleaning speed, pulsed laser parameters, and cleaning effect of the insulator were analyzed. At the highest laser scanning speed of 10m/s, the cleaning efficiency of 3.4cm2/s could be reached, and the optimized laser parameters of insulators with different materials were studied for provision of reference in electrical insulators laser cleaning application.
2022, 46(5): 653-656.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.012
Abstract:
In order to improve the wear resistance and corrosion resistance of TC4 alloy parts, the microstructure and comprehensive properties of laser cladding Fe35A coating on TC4 titanium alloy were analyzed through digital analysis and metallographic analysis. The results show that under the optimum parameters of laser power of 2.3kW, scanning speed of 9mm/s, and powder feeding rate of 10g/min, the best macro-morphology and good microstructure of the surface layer of TC4 is obtained. The Fe grain is refined, and the distribution is uniform. The high fusion degree between substrate and deposit is observed. The Rockwell hardness of the deposition layer is up to 40.2HRC, and the microhardness is up to 645.5HV. The overall mechanical properties of the deposition layer are obviously higher than that of the matrix. This research provides practical reference for the high quality repair and reuse of TC4 titanium alloy surface.
In order to improve the wear resistance and corrosion resistance of TC4 alloy parts, the microstructure and comprehensive properties of laser cladding Fe35A coating on TC4 titanium alloy were analyzed through digital analysis and metallographic analysis. The results show that under the optimum parameters of laser power of 2.3kW, scanning speed of 9mm/s, and powder feeding rate of 10g/min, the best macro-morphology and good microstructure of the surface layer of TC4 is obtained. The Fe grain is refined, and the distribution is uniform. The high fusion degree between substrate and deposit is observed. The Rockwell hardness of the deposition layer is up to 40.2HRC, and the microhardness is up to 645.5HV. The overall mechanical properties of the deposition layer are obviously higher than that of the matrix. This research provides practical reference for the high quality repair and reuse of TC4 titanium alloy surface.
2022, 46(5): 657-662.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.013
Abstract:
Methane and acetylene are the most important characteristic gases when the transformer breaks down. In order to meet the demand for detecting the concentration of the trace CH4 and C2H2 dissolved in the transformer, the laser photoacoustic spectroscopy gas detection technology was adopted. By analyzing the near-infrared absorption spectrum of CH4 and C2H2 gas, the appropriate laser light source was selected and the laser modulation parameters were determined. A set of photoacoustic spectroscopy trace CH4 and C2H2 gas detection system with dual laser light source and a non-resonant photoacoustic cell were designed, and the detection sensitivity and low concentration detection error of the system for CH4 and C2H2 gas was obtained. The result shows that CH4 and C2H2 have good response linearity in the volume fraction range of 0~1000×10-6 and 0~500×10-6, respectively, and the responsivities are 5.8969μV and 16.1831μV per 10-6 volume fraction, respectively. The system is tested for repeatability and accuracy using low-content CH4/C2H2 mixed gas. The maximum absolute error of detection is 0.30×10-6 when the CH4 volume fraction is 3.00×10-6, and the maximum absolute error of detection is 0.20×10-6 when the C2H2 volume fraction of 0.50×10-6. The research results meet the technical index requirements of measurement error and achieve high-sensitivity detection of trace CH4 and C2H2.
Methane and acetylene are the most important characteristic gases when the transformer breaks down. In order to meet the demand for detecting the concentration of the trace CH4 and C2H2 dissolved in the transformer, the laser photoacoustic spectroscopy gas detection technology was adopted. By analyzing the near-infrared absorption spectrum of CH4 and C2H2 gas, the appropriate laser light source was selected and the laser modulation parameters were determined. A set of photoacoustic spectroscopy trace CH4 and C2H2 gas detection system with dual laser light source and a non-resonant photoacoustic cell were designed, and the detection sensitivity and low concentration detection error of the system for CH4 and C2H2 gas was obtained. The result shows that CH4 and C2H2 have good response linearity in the volume fraction range of 0~1000×10-6 and 0~500×10-6, respectively, and the responsivities are 5.8969μV and 16.1831μV per 10-6 volume fraction, respectively. The system is tested for repeatability and accuracy using low-content CH4/C2H2 mixed gas. The maximum absolute error of detection is 0.30×10-6 when the CH4 volume fraction is 3.00×10-6, and the maximum absolute error of detection is 0.20×10-6 when the C2H2 volume fraction of 0.50×10-6. The research results meet the technical index requirements of measurement error and achieve high-sensitivity detection of trace CH4 and C2H2.
2022, 46(5): 663-667.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.014
Abstract:
In order to explain the local air pollution caused by the smoke produced by soldering leaded tin wire with electric soldering iron, an experimental system based on laser induced breakdown spectroscopy was designed to analyze the smoke produced by soldering leaded tin wire with electric soldering iron, and the characteristic spectral line of heavy metal lead was found in the smoke spectrum. Lead was quantitatively analyzed by internal standard method, and the detection limit of lead was 19.35×10-5 by fitting the curve. By analyzing the correlation between the plasma temperature and electron number density of lead, the validity of the experimental spectrum was verified. The results show that the experimental system and method of scene detection of electric soldering tin wire based on laser-induced breakdown spectrum have advantages of on-line, in-situ and fast when compared with the traditional chemical test method.
In order to explain the local air pollution caused by the smoke produced by soldering leaded tin wire with electric soldering iron, an experimental system based on laser induced breakdown spectroscopy was designed to analyze the smoke produced by soldering leaded tin wire with electric soldering iron, and the characteristic spectral line of heavy metal lead was found in the smoke spectrum. Lead was quantitatively analyzed by internal standard method, and the detection limit of lead was 19.35×10-5 by fitting the curve. By analyzing the correlation between the plasma temperature and electron number density of lead, the validity of the experimental spectrum was verified. The results show that the experimental system and method of scene detection of electric soldering tin wire based on laser-induced breakdown spectrum have advantages of on-line, in-situ and fast when compared with the traditional chemical test method.
2022, 46(5): 668-673.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.015
Abstract:
In order to solve the problems of component deformation and affecting manufacturing quality caused by the residual strain of material components, which is due to the residual stress after hot pressing by the difference of thermal expansion coefficient between resin matrix and carbon fiber in carbon fiber/epoxy resin composite components. The theoretical analysis and experimental verification were carried out by combining the on-line monitoring experimental research of fiber Bragg grating (FBG) sensor and finite element simulation analysis. The real-time data of surface residual strain of carbon fiber/epoxy composite ring components after hot pressing tank forming were collected. The results show that the strain release at the flange root is complex, the residual strain release near the support is blocked, and the residual strain at other monitoring points is generally 30με~90με. The results are consistent with the simulation results. FBG sensor can carry out multi-point real-time on-line monitoring of the residual strain release process after component forming, and realize the analysis and early warning of the overall strain distribution of the component. The research has certain scientific research and engineering application significance.
In order to solve the problems of component deformation and affecting manufacturing quality caused by the residual strain of material components, which is due to the residual stress after hot pressing by the difference of thermal expansion coefficient between resin matrix and carbon fiber in carbon fiber/epoxy resin composite components. The theoretical analysis and experimental verification were carried out by combining the on-line monitoring experimental research of fiber Bragg grating (FBG) sensor and finite element simulation analysis. The real-time data of surface residual strain of carbon fiber/epoxy composite ring components after hot pressing tank forming were collected. The results show that the strain release at the flange root is complex, the residual strain release near the support is blocked, and the residual strain at other monitoring points is generally 30με~90με. The results are consistent with the simulation results. FBG sensor can carry out multi-point real-time on-line monitoring of the residual strain release process after component forming, and realize the analysis and early warning of the overall strain distribution of the component. The research has certain scientific research and engineering application significance.
2022, 46(5): 674-679.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.016
Abstract:
In order to realize the precise measurement of the parallelism error, the laser collimating method of parallelism error measuring method based on position sensitive device (PSD) was proposed, and the experimental measurement system was designed. The divergence angle and spot size of the alignment laser beam were balanced by using the method of the second lens transformation of the inverted telescope structure. The optical path was turned by using an optical pentaprism, and then the position of a point relative to the measurement reference can be obtained in real time by PSD signal conditioning circuit as well as data acquisition and processing system. Then, the parallelism error between the toleranced feature and the datum feature can be quickly evaluated by using the minimum zone method, and the theoretical analysis and experimental verification were carried out. The experimental results show that the relative uncertainty of the measuring system is 0.077%, which has high measurement accuracy. It provides an effective measurement method for the precision measurement technology of parallelism error and has certain practical guiding significance.
In order to realize the precise measurement of the parallelism error, the laser collimating method of parallelism error measuring method based on position sensitive device (PSD) was proposed, and the experimental measurement system was designed. The divergence angle and spot size of the alignment laser beam were balanced by using the method of the second lens transformation of the inverted telescope structure. The optical path was turned by using an optical pentaprism, and then the position of a point relative to the measurement reference can be obtained in real time by PSD signal conditioning circuit as well as data acquisition and processing system. Then, the parallelism error between the toleranced feature and the datum feature can be quickly evaluated by using the minimum zone method, and the theoretical analysis and experimental verification were carried out. The experimental results show that the relative uncertainty of the measuring system is 0.077%, which has high measurement accuracy. It provides an effective measurement method for the precision measurement technology of parallelism error and has certain practical guiding significance.
2022, 46(5): 680-684.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.017
Abstract:
In order to take into account the characteristics of the optical network unit and the transmission rate of the user end, an integrable coherent detection scheme was used to replace the traditional direct detection scheme at the receiving end. The bias characteristics of the electro-absorption modulator (EAM) was analyzed. A 5km bidirectional access network communication system with a rate of 40Gbit/s was built, and the transmission test of the integrable optical network unit with the distributed feedback (DFB) laser and the EAM as the upstream transmitter was carried out. Under the direct detection scheme and forward error correction (FEC), the receiving sensitivity of downstream signal and upstream signal of bidirectional transmission are -18.31dBm and -17.94dBm respectively. Under the coherent detection scheme and FEC, the receiving sensitivities of downstream and upstream signals are -32.51dBm and -29.76dBm, respectively. The results show that the upstream and downstream receiving sensitivities of the coherent detection scheme are 14.20dB and 11.82dB higher than those of the direct detection scheme, respectively. The result of this work provides a high-speed and large-scale deployment integrated scheme for the optical network unit of the future client.
In order to take into account the characteristics of the optical network unit and the transmission rate of the user end, an integrable coherent detection scheme was used to replace the traditional direct detection scheme at the receiving end. The bias characteristics of the electro-absorption modulator (EAM) was analyzed. A 5km bidirectional access network communication system with a rate of 40Gbit/s was built, and the transmission test of the integrable optical network unit with the distributed feedback (DFB) laser and the EAM as the upstream transmitter was carried out. Under the direct detection scheme and forward error correction (FEC), the receiving sensitivity of downstream signal and upstream signal of bidirectional transmission are -18.31dBm and -17.94dBm respectively. Under the coherent detection scheme and FEC, the receiving sensitivities of downstream and upstream signals are -32.51dBm and -29.76dBm, respectively. The results show that the upstream and downstream receiving sensitivities of the coherent detection scheme are 14.20dB and 11.82dB higher than those of the direct detection scheme, respectively. The result of this work provides a high-speed and large-scale deployment integrated scheme for the optical network unit of the future client.
2022, 46(5): 685-690.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.018
Abstract:
In order to solve the problem of real-time monitoring the coupling efficiency of 10kW-level optic switch, a safety control method was adopted to monitor the coupling efficiency by detecting the backscattered light inside the working fiber at the output end of the optic switch in real time, and then its coupling failure was prevented. The mapping law and model between coupling errors and signal of backscattered light intensity were simulated and established. Furthermore, the safety control system of the optic switch was designed. And the effectiveness of the method was proved through the simulations and experiments. The results show that the high-power optic switch can carry more than 10kW power for a long time under the guarantee of the safety control system, and the coupling efficiency is stable above 98%. This research can ensure the long-term efficiency, stability and safety of 10kW-level optic switch. It can promote the autonomy of key components in the field of laser manufacturing in China.
In order to solve the problem of real-time monitoring the coupling efficiency of 10kW-level optic switch, a safety control method was adopted to monitor the coupling efficiency by detecting the backscattered light inside the working fiber at the output end of the optic switch in real time, and then its coupling failure was prevented. The mapping law and model between coupling errors and signal of backscattered light intensity were simulated and established. Furthermore, the safety control system of the optic switch was designed. And the effectiveness of the method was proved through the simulations and experiments. The results show that the high-power optic switch can carry more than 10kW power for a long time under the guarantee of the safety control system, and the coupling efficiency is stable above 98%. This research can ensure the long-term efficiency, stability and safety of 10kW-level optic switch. It can promote the autonomy of key components in the field of laser manufacturing in China.
2022, 46(5): 691-696.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.019
Abstract:
The evolution of the incoherent superposition of two nonparaxial Gaussian beams carried a C-dipole was theoretically and numerically studied. The results show that the position and degree of polarization of two C-points may change with variation of the relevant parameters. The slope of the axis of the C-dipole increases monotonically with propagation. For the case of non-paraxial beams, creation and annihilation of C-dipoles occur as the beams propagate to 0.01zR and 10.39zR, respectively. At the plane z=zR, the creation and annihilation of C-points respectively occurs when the waist width increases to 0.222μm and 0.56μm. Besides, the creation and annihilation of C-points may take place with variation of the off-axis parameter and the wavelength of the host nonparaxial beams. The results would be useful for deeply understanding singular optics and seeking for their potential applications.
The evolution of the incoherent superposition of two nonparaxial Gaussian beams carried a C-dipole was theoretically and numerically studied. The results show that the position and degree of polarization of two C-points may change with variation of the relevant parameters. The slope of the axis of the C-dipole increases monotonically with propagation. For the case of non-paraxial beams, creation and annihilation of C-dipoles occur as the beams propagate to 0.01zR and 10.39zR, respectively. At the plane z=zR, the creation and annihilation of C-points respectively occurs when the waist width increases to 0.222μm and 0.56μm. Besides, the creation and annihilation of C-points may take place with variation of the off-axis parameter and the wavelength of the host nonparaxial beams. The results would be useful for deeply understanding singular optics and seeking for their potential applications.
2022, 46(5): 697-701.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.020
Abstract:
To measure the damage threshold of multispectral filter induced by femtosecond laser, the laser damage threshold of front film of the multispectral filter was experimentally studied by a Ti∶sapphire femtosecond pulsed laser (800nm, 50fs), and the damage morphology of the front film of the filter was observed by a microscope. The results show that the damage thresholds of the front film under different pulse irradiation times (1, 2, 5, and 10) are 1.68J/cm2, 1.56J/cm2, 1.44J/cm2, and 1.42J/cm2, respectively. The damage threshold decreases with an increase in the pulse irradiation number. The repeated laser radiation will form a cumulative effect on the film. Because the width of the femtosecond laser is very short, the conduction band electrons in the film are produced by multiphoton ionization and quickly absorb the laser energy. When the electron energy is greater than the bandgap energy of the material, it will collide with the valence band electrons to produce another electron. A large number of free electrons are generated, resulting in film damage. Under the 1-on-1 and 2-on-1 test methods, the morphology of the damaged area of the front film becomes more apparent and regular with the increase of femtosecond laser fluence, and a clear layered structure gradually appears. The phenomenon is due to the different distribution of the interference field in the front film. This study provides a reference for the damage effect of multispectral filter film under femtosecond laser.
To measure the damage threshold of multispectral filter induced by femtosecond laser, the laser damage threshold of front film of the multispectral filter was experimentally studied by a Ti∶sapphire femtosecond pulsed laser (800nm, 50fs), and the damage morphology of the front film of the filter was observed by a microscope. The results show that the damage thresholds of the front film under different pulse irradiation times (1, 2, 5, and 10) are 1.68J/cm2, 1.56J/cm2, 1.44J/cm2, and 1.42J/cm2, respectively. The damage threshold decreases with an increase in the pulse irradiation number. The repeated laser radiation will form a cumulative effect on the film. Because the width of the femtosecond laser is very short, the conduction band electrons in the film are produced by multiphoton ionization and quickly absorb the laser energy. When the electron energy is greater than the bandgap energy of the material, it will collide with the valence band electrons to produce another electron. A large number of free electrons are generated, resulting in film damage. Under the 1-on-1 and 2-on-1 test methods, the morphology of the damaged area of the front film becomes more apparent and regular with the increase of femtosecond laser fluence, and a clear layered structure gradually appears. The phenomenon is due to the different distribution of the interference field in the front film. This study provides a reference for the damage effect of multispectral filter film under femtosecond laser.
2022, 46(5): 702-707.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.021
Abstract:
In order to discuss the acceleration of energy exchange between fine structure energy levels of alkali atoms by buffer gas, the energy transfer process of fine structure collision in Cs(Rb)-N2 system were investigated experimentally by laser induced fluorescence spectroscopy. The fluorescence data of D1 and D2 lines of alkali atoms were obtained under different conditions. The experimental results show that N2 molecules are more involved in the acceleration of fine structure energy exchange in the Cs-N2 system, and the system has a high fluorescence conversion efficiency at 340K. In the Rb-N2 system, N2 molecules mainly participate in the quenching process, and the gain effect on the fine structure collision is not obvious. The results can provide reference data for the efficient operation of the semiconductor pumped alkali laser.
In order to discuss the acceleration of energy exchange between fine structure energy levels of alkali atoms by buffer gas, the energy transfer process of fine structure collision in Cs(Rb)-N2 system were investigated experimentally by laser induced fluorescence spectroscopy. The fluorescence data of D1 and D2 lines of alkali atoms were obtained under different conditions. The experimental results show that N2 molecules are more involved in the acceleration of fine structure energy exchange in the Cs-N2 system, and the system has a high fluorescence conversion efficiency at 340K. In the Rb-N2 system, N2 molecules mainly participate in the quenching process, and the gain effect on the fine structure collision is not obvious. The results can provide reference data for the efficient operation of the semiconductor pumped alkali laser.
2022, 46(5): 708-712.
doi: 10.7510/jgjs.issn.1001-3806.2022.05.022
Abstract:
In order to study the influence of atmospheric turbulence on laser transmission characteristics with different wavelengths, the theoretical calculation was carried out by using MATLAB, and a turbulence simulation box was designed for experiment. The simulation results were compared with the experimental results for theoretical analysis and experimental verification. The intensity distribution of laser wavefront was observed and recorded. The beam drift and intensity fluctuation of different wavelength laser beams under the same atmospheric conditions were measured and analyzed. The effect of atmospheric turbulence on the polarization state of linearly polarized light was experimentally observed. The experimental results show that the intensity distribution of laser wavefront is easily affected with the enhancement of atmospheric turbulence. The intensity fluctuation of laser beam decreases with the increase of wavelength, and its variance is up to 2.79×10-2, the beam drift is independent of wavelength, and its variance is up to 9.11×10-12. Secondly, linearly polarized light is affected by turbulence effect, and its light intensity changes randomly, and its change degree is more intense with the increase of turbulence intensity. The experimental results are consistent with the atmospheric turbulence theory, which has a certain reference value for laser atmospheric transmission.
In order to study the influence of atmospheric turbulence on laser transmission characteristics with different wavelengths, the theoretical calculation was carried out by using MATLAB, and a turbulence simulation box was designed for experiment. The simulation results were compared with the experimental results for theoretical analysis and experimental verification. The intensity distribution of laser wavefront was observed and recorded. The beam drift and intensity fluctuation of different wavelength laser beams under the same atmospheric conditions were measured and analyzed. The effect of atmospheric turbulence on the polarization state of linearly polarized light was experimentally observed. The experimental results show that the intensity distribution of laser wavefront is easily affected with the enhancement of atmospheric turbulence. The intensity fluctuation of laser beam decreases with the increase of wavelength, and its variance is up to 2.79×10-2, the beam drift is independent of wavelength, and its variance is up to 9.11×10-12. Secondly, linearly polarized light is affected by turbulence effect, and its light intensity changes randomly, and its change degree is more intense with the increase of turbulence intensity. The experimental results are consistent with the atmospheric turbulence theory, which has a certain reference value for laser atmospheric transmission.
