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RSS2017 Vol. 41, No. 3
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2017, 41(3): 307-311.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.001
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Abstract:
In order to stuy the de-orbiting mechanism of small scale space debris, the models of spinning and non-spinning space debris were established. The variation of space debris velocity ablating by ground-based laser was analyzed theoretically. Orbit maneuver mode of space debris irradiating by laser was investigated. The variations of perigee and apogee altitudes, semi-major axis and eccentricity with the change of initial true anomaly of the space debris under the irradiation of high-energy pulse laser were simulated and analyzed. The simulation results show that there is an optimal action area of removal of space debris using ground-based laser. The de-orbiting effect of spin debris is the best with initial true anomaly in the range of 86°~151°. The de-orbiting effect of non-spinning debris is the best with initial true anomaly in the range of 130°~162°. The de-orbiting effect of spinning debris is superior to non-spinning debris.
In order to stuy the de-orbiting mechanism of small scale space debris, the models of spinning and non-spinning space debris were established. The variation of space debris velocity ablating by ground-based laser was analyzed theoretically. Orbit maneuver mode of space debris irradiating by laser was investigated. The variations of perigee and apogee altitudes, semi-major axis and eccentricity with the change of initial true anomaly of the space debris under the irradiation of high-energy pulse laser were simulated and analyzed. The simulation results show that there is an optimal action area of removal of space debris using ground-based laser. The de-orbiting effect of spin debris is the best with initial true anomaly in the range of 86°~151°. The de-orbiting effect of non-spinning debris is the best with initial true anomaly in the range of 130°~162°. The de-orbiting effect of spinning debris is superior to non-spinning debris.
2017, 41(3): 312-317.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.002
Abstract:
In order to meet the demands of space debris detection and precise orbit determination, by using high sensitive laser detection method with photon counting and the principle of photon counting detection of avalanche detector based on Geiger mode, space-based photon counting detection model was established on the relative radial velocity of detector and space debris. After theoretical analysis and simulation verification of photon counting laser detection of space debris, the results show that photon counting laser detection can effectively detect space debris(size of 10cm) and the average ranging error is 34.72cm. Its ranging accuracy could be improved 3 orders of magnitude compared with world traditional ground-based radar and photon-electronic technology. It can effectively reduce collision probability of spacecraft.
In order to meet the demands of space debris detection and precise orbit determination, by using high sensitive laser detection method with photon counting and the principle of photon counting detection of avalanche detector based on Geiger mode, space-based photon counting detection model was established on the relative radial velocity of detector and space debris. After theoretical analysis and simulation verification of photon counting laser detection of space debris, the results show that photon counting laser detection can effectively detect space debris(size of 10cm) and the average ranging error is 34.72cm. Its ranging accuracy could be improved 3 orders of magnitude compared with world traditional ground-based radar and photon-electronic technology. It can effectively reduce collision probability of spacecraft.
2017, 41(3): 318-321.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.003
Abstract:
In order to study effect of 1070nm continuous wave (CW) laser irradiation on three-junction GaAs solar cells, rear surface temperature and load voltage of a solar cell under different power densities were measured. Under 8.4W/cm2 laser irradiation, the temperature increased obviously and load voltage decreased nearly to zero. The load voltage only recovered to 53% of the initial value after irradiation. With the increasing of power density to 11.7W/cm2, the load voltage decreased to zero after 2.3s. Furthermore, the cell was damaged and can't be recovered. The results show that the temperature of a solar cell rises significantly and the load voltage deceases when irradiated by CW laser. When laser power density is small, the rise of cell temperature is small and the drop of load voltage is also small. The load voltage can be restored to the initial state with the stop of laser irradiation. When laser power density is large, the rise of cell temperature is large and load voltage decreases significantly. Even with the stop of laser, the load voltage can not be restored to the initial value and the cell is damaged. The experiment results can provide reference basis for the research of damage mechanism of solar cells under laser irradiation.
In order to study effect of 1070nm continuous wave (CW) laser irradiation on three-junction GaAs solar cells, rear surface temperature and load voltage of a solar cell under different power densities were measured. Under 8.4W/cm2 laser irradiation, the temperature increased obviously and load voltage decreased nearly to zero. The load voltage only recovered to 53% of the initial value after irradiation. With the increasing of power density to 11.7W/cm2, the load voltage decreased to zero after 2.3s. Furthermore, the cell was damaged and can't be recovered. The results show that the temperature of a solar cell rises significantly and the load voltage deceases when irradiated by CW laser. When laser power density is small, the rise of cell temperature is small and the drop of load voltage is also small. The load voltage can be restored to the initial state with the stop of laser irradiation. When laser power density is large, the rise of cell temperature is large and load voltage decreases significantly. Even with the stop of laser, the load voltage can not be restored to the initial value and the cell is damaged. The experiment results can provide reference basis for the research of damage mechanism of solar cells under laser irradiation.
2017, 41(3): 322-327.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.004
Abstract:
To explore characteristics and rules of weld formation of aluminum alloy by high power fiber laser welding, 3mm-thick 5052 aluminum alloy was welded by laser with Gaussian and flat-topped beams respectively. The influence of weld formation characteristics, laser power and scanning speed on weld shape was analyzed comparatively. The results show that flat-top beam welding is mainly of thermal conductivity mode, and weld pool is U type, which is easy to produce pores, cracks and other defects. Gaussian beam welding has 4 modes. 4 modes are transformed mutually with the change of laser power and scanning rate. Weld pool is丁type under deep penetration mode. At scan rate of 20mm/s, the lower and upper critical power density of effective deep penetration welding of Gaussian beam are 8.8×105W/cm2 and 9.2×105W/cm2. With laser power of 2.7kW, the lower and upper critical power of effective deep penetration welding of Gaussian beam are 77J/mm and 90J/mm. Under the premise of the required welding power density, line energy can be used as the criterion of laser deep penetration welding. Line energy and power density play decisive role in welding mode and pool shape.
To explore characteristics and rules of weld formation of aluminum alloy by high power fiber laser welding, 3mm-thick 5052 aluminum alloy was welded by laser with Gaussian and flat-topped beams respectively. The influence of weld formation characteristics, laser power and scanning speed on weld shape was analyzed comparatively. The results show that flat-top beam welding is mainly of thermal conductivity mode, and weld pool is U type, which is easy to produce pores, cracks and other defects. Gaussian beam welding has 4 modes. 4 modes are transformed mutually with the change of laser power and scanning rate. Weld pool is丁type under deep penetration mode. At scan rate of 20mm/s, the lower and upper critical power density of effective deep penetration welding of Gaussian beam are 8.8×105W/cm2 and 9.2×105W/cm2. With laser power of 2.7kW, the lower and upper critical power of effective deep penetration welding of Gaussian beam are 77J/mm and 90J/mm. Under the premise of the required welding power density, line energy can be used as the criterion of laser deep penetration welding. Line energy and power density play decisive role in welding mode and pool shape.
2017, 41(3): 328-331.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.005
Abstract:
To optimize the sensitivity of surface plasmon resonance (SPR) sensors, the reflectivity and sensitivity variances of bimetallic film SPR sensors with the change of silver-gold film thickness were studied based on thin film theory. The thickness of silver film and gold film had a certain range under the condition that resonance angle reflectivity was less than 1%. In the range of thickness, the sensitivity of bimetallic film SPR sensor increases with the increase of the thickness of silver film (or gold film). The increment of sensitivity was up to 5°/RIU. The results indicate that the sensitivity of bimetallic film SPR sensor can be improved by increasing the thickness of bimetallic film under the premise of certain resonance angle reflectivity.
To optimize the sensitivity of surface plasmon resonance (SPR) sensors, the reflectivity and sensitivity variances of bimetallic film SPR sensors with the change of silver-gold film thickness were studied based on thin film theory. The thickness of silver film and gold film had a certain range under the condition that resonance angle reflectivity was less than 1%. In the range of thickness, the sensitivity of bimetallic film SPR sensor increases with the increase of the thickness of silver film (or gold film). The increment of sensitivity was up to 5°/RIU. The results indicate that the sensitivity of bimetallic film SPR sensor can be improved by increasing the thickness of bimetallic film under the premise of certain resonance angle reflectivity.
2017, 41(3): 332-336.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.006
Abstract:
In order to improve the quality of in-focus reconstructed images, random phase pupil was used to replace the pinhole in optical scanning holography system. After theoretical analysis and experimental verification, the comparison of signal to noise ratio, correlation coefficient and frequency spectrum distribution between the original and reconstructed images in the optical scanning holography system and the system based on random phase pupil was gotten respectively. The results show that under the same experimental condition, the reconstructed image from optical scanning holography based on random phase encoding has higher signal-to-noise ratio and correlation coefficient. The change trend of the reconstructed image spectrum is similar to that of the original image.
In order to improve the quality of in-focus reconstructed images, random phase pupil was used to replace the pinhole in optical scanning holography system. After theoretical analysis and experimental verification, the comparison of signal to noise ratio, correlation coefficient and frequency spectrum distribution between the original and reconstructed images in the optical scanning holography system and the system based on random phase pupil was gotten respectively. The results show that under the same experimental condition, the reconstructed image from optical scanning holography based on random phase encoding has higher signal-to-noise ratio and correlation coefficient. The change trend of the reconstructed image spectrum is similar to that of the original image.
2017, 41(3): 337-341.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.007
Abstract:
In order to improve the splicing quality of large mode area double-cladding fiber, an optical power alignment system was designed by using NUFERN 20/400μm double-cladding fiber. The cladding light in the cladding layer and the basic-mode light in the core were verified. The relationship between core dislocation and coupling efficiency was analyzed theoretically and verified experimentally. The existence of the cladding light or the higher-order mode in the core reduced the sensitivity of coupling efficiency to core dislocation. After stripping the cladding light and the higher-order mode, the coupling efficiency varies with core dislocation as Gaussian shape. A double-ended pumping fiber laser system with kW level output power was built by using the optical power alignment system, with the maximum output power of 1170W, optical-to-optical conversion efficiency of about 73% and beam quality factor of around 1.22. Quasi-single-mode output of kW level was gotten. The results show that accurate alignment of double-caldding fiber can be achieved with optical power alignment technique. The study is important for the improvement of output performance of high power fiber lasers.
In order to improve the splicing quality of large mode area double-cladding fiber, an optical power alignment system was designed by using NUFERN 20/400μm double-cladding fiber. The cladding light in the cladding layer and the basic-mode light in the core were verified. The relationship between core dislocation and coupling efficiency was analyzed theoretically and verified experimentally. The existence of the cladding light or the higher-order mode in the core reduced the sensitivity of coupling efficiency to core dislocation. After stripping the cladding light and the higher-order mode, the coupling efficiency varies with core dislocation as Gaussian shape. A double-ended pumping fiber laser system with kW level output power was built by using the optical power alignment system, with the maximum output power of 1170W, optical-to-optical conversion efficiency of about 73% and beam quality factor of around 1.22. Quasi-single-mode output of kW level was gotten. The results show that accurate alignment of double-caldding fiber can be achieved with optical power alignment technique. The study is important for the improvement of output performance of high power fiber lasers.
2017, 41(3): 342-345.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.008
Abstract:
In order to measure high intensity femtosecond laser with single-shot precisely in real-time, a real-time measurement system was designed via processing data from a single-shot autocorrelator with LabVIEW. The precision is highly improved with signal noise decreased by limiting image processing area and integrating the image data. The autocorrelator was calibrated on-line by means of self-calibration, and pulse duration was obtained in real time. The precision of 3.6fs per pixel was obtained with small-pixel-size CCD. Ti:sapphire laser with pulsewidth of 50fs and center wavelength of 800nm was measured in real-time with our developed device. The results prove that femtosecond pulses can be measured precisely in real-time with a single-shot autocorrelator based on LabVIEW.
In order to measure high intensity femtosecond laser with single-shot precisely in real-time, a real-time measurement system was designed via processing data from a single-shot autocorrelator with LabVIEW. The precision is highly improved with signal noise decreased by limiting image processing area and integrating the image data. The autocorrelator was calibrated on-line by means of self-calibration, and pulse duration was obtained in real time. The precision of 3.6fs per pixel was obtained with small-pixel-size CCD. Ti:sapphire laser with pulsewidth of 50fs and center wavelength of 800nm was measured in real-time with our developed device. The results prove that femtosecond pulses can be measured precisely in real-time with a single-shot autocorrelator based on LabVIEW.
2017, 41(3): 346-350.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.009
Abstract:
In order to obtain the optimal laser cutting quality and efficiency of polycrystalline cubic boron nitride(PCBN), the ablation threshold of PCBN material was obtained as 1.796J/cm2, based on the function relationship between the ablation diameter and laser energy. Cutting experiments of model BN250 PCBN with Nd:YAG laser were carried out. The effects of cutting speed, laser power and pulse repetition rate on cutting quality were analyzed. The changing trend of slit width of PCBN under different laser parameters was summarized by contrasting the microscopic observation. The results show that, the best quality of slit and the higher cutting efficiency can be obtained at the condition of laser power 28W, pulse repetition rate 60Hz, and cutting speed 20mm/min, by laser pulse with pulse duration 100μs. The method and process data have an important reference value for laser processing of PCBN or other superhard materials.
In order to obtain the optimal laser cutting quality and efficiency of polycrystalline cubic boron nitride(PCBN), the ablation threshold of PCBN material was obtained as 1.796J/cm2, based on the function relationship between the ablation diameter and laser energy. Cutting experiments of model BN250 PCBN with Nd:YAG laser were carried out. The effects of cutting speed, laser power and pulse repetition rate on cutting quality were analyzed. The changing trend of slit width of PCBN under different laser parameters was summarized by contrasting the microscopic observation. The results show that, the best quality of slit and the higher cutting efficiency can be obtained at the condition of laser power 28W, pulse repetition rate 60Hz, and cutting speed 20mm/min, by laser pulse with pulse duration 100μs. The method and process data have an important reference value for laser processing of PCBN or other superhard materials.
2017, 41(3): 351-355.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.010
Abstract:
In order to improve the validity and reliability of terahertz non destructive testing (NDT), a set of visualization system for terahertz NDT was set up. Terahertz frequency modulation continuous wave imaging devices was adopted to collect data, MATLAB-graphical user interface (GUI) was used to develop a set of visualization software platform integrating function such as image processing and 3-D reconstruction. After the analysis of the data, the prototype system was used to detect polymer insulation tiles with the containing of internal metal. The results show that the terahertz NDT visualization system is constructed to observe the internal structure of polymer insulation tile effectively, and then by using the internal image of software platform, after reasonable analysis and algorithm processing, the size and shape of the embedded metal defects are displayed directly on the computer. The accuracy of non-destructive testing is increased, and the difficulty of terahertz nondestructive testing and data analysis duration are decreased.
In order to improve the validity and reliability of terahertz non destructive testing (NDT), a set of visualization system for terahertz NDT was set up. Terahertz frequency modulation continuous wave imaging devices was adopted to collect data, MATLAB-graphical user interface (GUI) was used to develop a set of visualization software platform integrating function such as image processing and 3-D reconstruction. After the analysis of the data, the prototype system was used to detect polymer insulation tiles with the containing of internal metal. The results show that the terahertz NDT visualization system is constructed to observe the internal structure of polymer insulation tile effectively, and then by using the internal image of software platform, after reasonable analysis and algorithm processing, the size and shape of the embedded metal defects are displayed directly on the computer. The accuracy of non-destructive testing is increased, and the difficulty of terahertz nondestructive testing and data analysis duration are decreased.
2017, 41(3): 356-360.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.011
Abstract:
In order to study influence of incident light on electro-optic characteristics of liquid crystal, the optical properties of liquid crystal were analyzed theoretically based on Jones matrix. By using semiconductor laser with different wavelengths as incident light, electro optical characteristics of liquid crystal were studied experimentally. The results show that the transmission intensity of the liquid crystal sample descends steeply at 4.8V and the threshold voltage of liquid crystal is independent on the wavelength of light source. The oscillograph images show that the incident light affects the response time obviously. The diffraction facula of liquid crystal sample arranges in a ring first and gradually in a line with the increase of voltage. At the same time, diffraction spot is not completely symmetrical. The spatial and energy distributions of the diffraction spot are determined by incident wavelength and power supply voltage. The study is meaningful for the research and development of liquid crystal devices.
In order to study influence of incident light on electro-optic characteristics of liquid crystal, the optical properties of liquid crystal were analyzed theoretically based on Jones matrix. By using semiconductor laser with different wavelengths as incident light, electro optical characteristics of liquid crystal were studied experimentally. The results show that the transmission intensity of the liquid crystal sample descends steeply at 4.8V and the threshold voltage of liquid crystal is independent on the wavelength of light source. The oscillograph images show that the incident light affects the response time obviously. The diffraction facula of liquid crystal sample arranges in a ring first and gradually in a line with the increase of voltage. At the same time, diffraction spot is not completely symmetrical. The spatial and energy distributions of the diffraction spot are determined by incident wavelength and power supply voltage. The study is meaningful for the research and development of liquid crystal devices.
2017, 41(3): 361-366.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.012
Abstract:
Etching diffraction grating (EDG), one of the most critical components, can achieve wavelength division multiplex (WDM) function and realize on-chip optical interconnection. In order to realize 4-channel EDG with the wavelength spacing of 20nm at 1310nm wavelength, Kirchhoff scalar diffraction theory was used for theory design and simulation verification. To further improve the reflection efficiency and decrease the insertion loss, Bragg reflection gratings were designed to replace the normal etched facets. Multimode interference (MMI) coupler was also introduced at input waveguide for flat-top frequency response. The simulation results demonstrate the reflection efficiency of grating reflective surface is up to 85% and 1dB bandwidth is up to 12nm. The designed EDG has a significant effect on improving system stability, increasing transmission distance and capacity, and reducing system cost. The design can meet the practical application requirements of optical interconnection system.
Etching diffraction grating (EDG), one of the most critical components, can achieve wavelength division multiplex (WDM) function and realize on-chip optical interconnection. In order to realize 4-channel EDG with the wavelength spacing of 20nm at 1310nm wavelength, Kirchhoff scalar diffraction theory was used for theory design and simulation verification. To further improve the reflection efficiency and decrease the insertion loss, Bragg reflection gratings were designed to replace the normal etched facets. Multimode interference (MMI) coupler was also introduced at input waveguide for flat-top frequency response. The simulation results demonstrate the reflection efficiency of grating reflective surface is up to 85% and 1dB bandwidth is up to 12nm. The designed EDG has a significant effect on improving system stability, increasing transmission distance and capacity, and reducing system cost. The design can meet the practical application requirements of optical interconnection system.
2017, 41(3): 367-375.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.013
Abstract:
Surface roughness of silicon-on-insulator(SOI) nano-optical waveguide can significantly increase scattering loss. It is one of the problems to be solved urgently in different application fields. Firstly, the concept of surface roughness and the progress of theoretical research of surface scattering loss were introduced. Secondly, various advanced measurement methods of surface roughness of SOI nano-optical waveguide, including the problems existing in the characterization of surface topography, were reviewed. Thirdly, several kinds of surface smoothing processes were also introduced. Finally, some conclusions were presented combined with our study.
Surface roughness of silicon-on-insulator(SOI) nano-optical waveguide can significantly increase scattering loss. It is one of the problems to be solved urgently in different application fields. Firstly, the concept of surface roughness and the progress of theoretical research of surface scattering loss were introduced. Secondly, various advanced measurement methods of surface roughness of SOI nano-optical waveguide, including the problems existing in the characterization of surface topography, were reviewed. Thirdly, several kinds of surface smoothing processes were also introduced. Finally, some conclusions were presented combined with our study.
2017, 41(3): 376-379.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.014
Abstract:
In order to detect obstacles and locate mobile robots in mobile robot navigation under dark environment, a novel visual navigation method based on grating projection stereo vision was proposed. At first, by combining with grating projection profilometry of plane structured light and stereo vision technology, the geometry and mathematical model of a grating projection stereo vision sensor were founded. Then, the method of space equipment position constraint and projection plane intersection were used and 3-D coordinates of the object in field of view of robot were calculated. A reliable and real method of obstacle detection and analysis was established. After theoretical analysis and experimental verification, the caculated range precision of 0.8mm was obtained. The results show that the method can achieve sub-pixel accuracy in image computation. The study can be used to overcome the problem that the robot can't navigate autonomously in dark environment and provides a basis of robot navigation without global positioning system support in dark environment.
In order to detect obstacles and locate mobile robots in mobile robot navigation under dark environment, a novel visual navigation method based on grating projection stereo vision was proposed. At first, by combining with grating projection profilometry of plane structured light and stereo vision technology, the geometry and mathematical model of a grating projection stereo vision sensor were founded. Then, the method of space equipment position constraint and projection plane intersection were used and 3-D coordinates of the object in field of view of robot were calculated. A reliable and real method of obstacle detection and analysis was established. After theoretical analysis and experimental verification, the caculated range precision of 0.8mm was obtained. The results show that the method can achieve sub-pixel accuracy in image computation. The study can be used to overcome the problem that the robot can't navigate autonomously in dark environment and provides a basis of robot navigation without global positioning system support in dark environment.
2017, 41(3): 380-384.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.015
Abstract:
To further improve the velocity of deep laser drilling in thick metal plate, aiming at 5mm thick stainless steel plate, laser drilling method of long pulse laser with high pulse energy superposed by short pulse laser with high peak power was put forward. The theoretical model of laser drilling by superposed pulsed lasers was established. The function of long pulse laser with high pulse energy was to melt metals, while the removal of metal melted things relied mainly on short pulse laser of high peak power. The drilling effects under different laser parameters (pulse energy, pulse width and drilling method) were studied. The results show that, compared with laser drilling by single long pulse, laser drilling by the superposed pulse can substantially reduce the drilling time. For long pulse of 2ms pulse width and 2.9J pulse energy, the drilling velocity of superposed pulsed lasers increases by 2.3 times while the energy cost reduces 20%. And the larger the pulse energy is, the narrower the pulse width is, the faster the drilling velocity becomes. The study provides a basis for laser selection in laser drilling by the superposed pulsed lasers.
To further improve the velocity of deep laser drilling in thick metal plate, aiming at 5mm thick stainless steel plate, laser drilling method of long pulse laser with high pulse energy superposed by short pulse laser with high peak power was put forward. The theoretical model of laser drilling by superposed pulsed lasers was established. The function of long pulse laser with high pulse energy was to melt metals, while the removal of metal melted things relied mainly on short pulse laser of high peak power. The drilling effects under different laser parameters (pulse energy, pulse width and drilling method) were studied. The results show that, compared with laser drilling by single long pulse, laser drilling by the superposed pulse can substantially reduce the drilling time. For long pulse of 2ms pulse width and 2.9J pulse energy, the drilling velocity of superposed pulsed lasers increases by 2.3 times while the energy cost reduces 20%. And the larger the pulse energy is, the narrower the pulse width is, the faster the drilling velocity becomes. The study provides a basis for laser selection in laser drilling by the superposed pulsed lasers.
2017, 41(3): 385-390.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.016
Abstract:
In order to correct the error between wind field information measured by a tilt lidar and the actual wind field, after analyzing the measurement principle, placement and exist problems of laser radar, theoretical calculation was carried out based on space coordinate transformation method and correction formula was put forward. After comparing the measured data of laser radar located at horizontal position and lateral tilt 7.2°, it was found that the error of vertical airflow data measured by tilt lidar was larger. After modification, data curve is in good agreement with the modified algorithm. The results indicate that could get the real wind field information can be obtained correctly based on space coordinate transformation algorithm for tilt lidar. Correctness and feasibility of the algorithm are proved.
In order to correct the error between wind field information measured by a tilt lidar and the actual wind field, after analyzing the measurement principle, placement and exist problems of laser radar, theoretical calculation was carried out based on space coordinate transformation method and correction formula was put forward. After comparing the measured data of laser radar located at horizontal position and lateral tilt 7.2°, it was found that the error of vertical airflow data measured by tilt lidar was larger. After modification, data curve is in good agreement with the modified algorithm. The results indicate that could get the real wind field information can be obtained correctly based on space coordinate transformation algorithm for tilt lidar. Correctness and feasibility of the algorithm are proved.
2017, 41(3): 391-395.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.017
Abstract:
In order to decrease the effect of laser-induced ultrasound on real-time performance and effectiveness of underwater remote sensing, the theory of laser-induced ultrasound and photoacoustic effect was analyzed. Character encoding was achieved by speech recognition technology. Baseband encoding for speech and code structure of controlling laser emission were discussed. The system of experimental measurement was set up. Pulse laser of 1.06μm wavelength was used to induce underwater ultrasound. By collecting and processing underwater laser-induced sound signals, real-time voice control from air platform in laboratory to underwater target could be accomplished. The experimental results show that, recognition and encoding for speaker-independent voice commands can realize the control of underwater target induced by laser ultrasound with adjustable baseband frequency. The study provides a new approach for underwater remote sensing with laser-induced ultrasound.
In order to decrease the effect of laser-induced ultrasound on real-time performance and effectiveness of underwater remote sensing, the theory of laser-induced ultrasound and photoacoustic effect was analyzed. Character encoding was achieved by speech recognition technology. Baseband encoding for speech and code structure of controlling laser emission were discussed. The system of experimental measurement was set up. Pulse laser of 1.06μm wavelength was used to induce underwater ultrasound. By collecting and processing underwater laser-induced sound signals, real-time voice control from air platform in laboratory to underwater target could be accomplished. The experimental results show that, recognition and encoding for speaker-independent voice commands can realize the control of underwater target induced by laser ultrasound with adjustable baseband frequency. The study provides a new approach for underwater remote sensing with laser-induced ultrasound.
2017, 41(3): 396-401.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.018
Abstract:
To overcome the shortcomings of polarizers currently used in terahertz frequency region, which are expensive to produce, difficult to be processed, and easy to generate Fabry-Perot echo effect, a new terahertz polarizer was presented by means of Brewster effect of a stack of silicon wafers. According to the principle that the different oil with different compounds and different concentration has the different optical activity of terahertz wave, by using the polarizer, the optical activity of 97# gasoline, diesel oil and the mixed oil samples were measured to be identificated. The results show that, the extinction ratio of the designed polarizer is higher than 1059 and transmittance is higher than 99% and the polarizer can be used in 0THz~3THz frequency region. By using the silicon wafer polarizer, the optical activity of 97# gasoline, diesel oil and their mixture is measured. And the qualitative and quantitative detection of oil is realized. The design of polarizer meets the requirement of polarizer in terahertz frequency region.
To overcome the shortcomings of polarizers currently used in terahertz frequency region, which are expensive to produce, difficult to be processed, and easy to generate Fabry-Perot echo effect, a new terahertz polarizer was presented by means of Brewster effect of a stack of silicon wafers. According to the principle that the different oil with different compounds and different concentration has the different optical activity of terahertz wave, by using the polarizer, the optical activity of 97# gasoline, diesel oil and the mixed oil samples were measured to be identificated. The results show that, the extinction ratio of the designed polarizer is higher than 1059 and transmittance is higher than 99% and the polarizer can be used in 0THz~3THz frequency region. By using the silicon wafer polarizer, the optical activity of 97# gasoline, diesel oil and their mixture is measured. And the qualitative and quantitative detection of oil is realized. The design of polarizer meets the requirement of polarizer in terahertz frequency region.
2017, 41(3): 402-405.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.019
Abstract:
In order to study splitting characteristics of micro-angle beam splitting polarization prisms, according to optical properties of calcite crystals, from propagation direction of the light in incident interface, exit interface, and prism internal, the relationship between splitting angle and wavelength was analyzed at normal incidence. For a certain wavelength, the influence of incident angle on beam splitting angle was analyzed. After the experiment of three prism samples, the results show that splitting angle of a micro-angle beam splitting polarization prism changes with the change of wavelength of the incident light. The shorter the wavelength, the greater the splitting angle. In the principal cross section of prism, the change range of incident angle is of -20°~20° and splitting angle increases nonlinearly. The results have certain value for the design and usage of micro-angle beam splitting polarization prisms.
In order to study splitting characteristics of micro-angle beam splitting polarization prisms, according to optical properties of calcite crystals, from propagation direction of the light in incident interface, exit interface, and prism internal, the relationship between splitting angle and wavelength was analyzed at normal incidence. For a certain wavelength, the influence of incident angle on beam splitting angle was analyzed. After the experiment of three prism samples, the results show that splitting angle of a micro-angle beam splitting polarization prism changes with the change of wavelength of the incident light. The shorter the wavelength, the greater the splitting angle. In the principal cross section of prism, the change range of incident angle is of -20°~20° and splitting angle increases nonlinearly. The results have certain value for the design and usage of micro-angle beam splitting polarization prisms.
2017, 41(3): 406-410.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.020
Abstract:
In order to obtain accurate wavefront reconstruction field of digital holography, theoretical analysis and experiments of common wavefront reconstruction algorithms were made. Equivalent distance of light wave propagating through single medium was obtained. The related parameters commonly used in wavefront reconstruction formula were modified by using equivalent distance. The results of reconstruction of digital hologram with Collins formula and with equivalent distance were compared and analyzed. It was found that when light passing through non single medium, accurate digital holographic image could be obtained by reconstruction formula using Collins formula or equivalent distance correction. The results show that the results of wavefront reconstruction using equivalent distance of digital hologram are consistent with the results obtained by Collins formula reconstruction. This method can be used to simplify wavefront reconstruction of digital hologram when light wave passes through single medium. The results provide useful reference for microscopic digital holography and application of digital holography detection.
In order to obtain accurate wavefront reconstruction field of digital holography, theoretical analysis and experiments of common wavefront reconstruction algorithms were made. Equivalent distance of light wave propagating through single medium was obtained. The related parameters commonly used in wavefront reconstruction formula were modified by using equivalent distance. The results of reconstruction of digital hologram with Collins formula and with equivalent distance were compared and analyzed. It was found that when light passing through non single medium, accurate digital holographic image could be obtained by reconstruction formula using Collins formula or equivalent distance correction. The results show that the results of wavefront reconstruction using equivalent distance of digital hologram are consistent with the results obtained by Collins formula reconstruction. This method can be used to simplify wavefront reconstruction of digital hologram when light wave passes through single medium. The results provide useful reference for microscopic digital holography and application of digital holography detection.
2017, 41(3): 411-415.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.021
Abstract:
In order to study effect of different modulations on performance of wireless ultraviolet(UV) communication systems in atmospheric turbulence, the expressions of bit error rate (BER) using on-off keying(OOK) and pulse position modulation (PPM) based on UV non-line-of-sight(NLOS) communication model in weak turbulence were derived. Helicopter landing model using UV guiding technology was introduced and effect of transmission power, range, transmitter (Tx) beam divergence, receiver (Rx) field of view (FOV), Tx and Rx elevation angle on BER under different modulations were simulated. The results show that BER under different modulations decreases with the increase of transmitted power, Tx beam angle and Rx FOV, while increases with the increase of range, Tx and Rx elevation angle. Under the same condition, PPM has a better BER performance than OOK. BER decreases with the increasing of modulation order. The results have applicable values for improving the jamming-rejection capability of ultraviolet communication systems in atmospheric turbulence.
In order to study effect of different modulations on performance of wireless ultraviolet(UV) communication systems in atmospheric turbulence, the expressions of bit error rate (BER) using on-off keying(OOK) and pulse position modulation (PPM) based on UV non-line-of-sight(NLOS) communication model in weak turbulence were derived. Helicopter landing model using UV guiding technology was introduced and effect of transmission power, range, transmitter (Tx) beam divergence, receiver (Rx) field of view (FOV), Tx and Rx elevation angle on BER under different modulations were simulated. The results show that BER under different modulations decreases with the increase of transmitted power, Tx beam angle and Rx FOV, while increases with the increase of range, Tx and Rx elevation angle. Under the same condition, PPM has a better BER performance than OOK. BER decreases with the increasing of modulation order. The results have applicable values for improving the jamming-rejection capability of ultraviolet communication systems in atmospheric turbulence.
2017, 41(3): 416-420.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.022
Abstract:
In order to make the laser beam of linear-array semiconductor laser be better used in laser remote wireless power transmission, a linear-array semiconductor laser beam shaping system based on the set of optical wedges, curved mirrors and prisms was designed. The parameters of components in the system and the theoretical shaping results were derived by numerical calculation. After then the realistic components were processed and the experimental shaping system was built. The experimental results were that the laser spot size after shaping was 9.9cm×9.6cm, energy uniformity was 68.9%, and energy transfer efficiency was 71.3%. The beam quality could meet the requirement of light cell at receiving end for laser space uniformity. The reason of the difference between the simulated and experimental system was analyzed. The results show that the system can simultaneously realize the expanding and collimation of laser beam array along fast axis and slow axis. The system can also adjust the shape and the uniformity of output light spot with less optical components. Light cell components are the key processes of laser wireless power transmission. The study has great practical value for laser conversion efficiency.
In order to make the laser beam of linear-array semiconductor laser be better used in laser remote wireless power transmission, a linear-array semiconductor laser beam shaping system based on the set of optical wedges, curved mirrors and prisms was designed. The parameters of components in the system and the theoretical shaping results were derived by numerical calculation. After then the realistic components were processed and the experimental shaping system was built. The experimental results were that the laser spot size after shaping was 9.9cm×9.6cm, energy uniformity was 68.9%, and energy transfer efficiency was 71.3%. The beam quality could meet the requirement of light cell at receiving end for laser space uniformity. The reason of the difference between the simulated and experimental system was analyzed. The results show that the system can simultaneously realize the expanding and collimation of laser beam array along fast axis and slow axis. The system can also adjust the shape and the uniformity of output light spot with less optical components. Light cell components are the key processes of laser wireless power transmission. The study has great practical value for laser conversion efficiency.
2017, 41(3): 421-426.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.023
Abstract:
In order to study influence of the surface shape of reference wave on lens focal length, digital holography method was used for theoretical analysis and experimental verification. Focal length was measured respectively with planar reference wave and spherical reference wave at different wavelengths. And then, the measured values were compared with the nominal values and the theoretical calculation values. The results show that the relative errors are above 5% between the measured value, the nominal value and the theoretical calculation value with planar reference wave. The relative errors are blow 2% with spherical reference wave. Therefore, the precision of focal length measured by spherical reference wave is higher. After calculation, focal lengths measured by two different reference lights are within the range of theoretical depth of focal. Therefore, the reconstructed image obtained by the measured value is equivalent to the reconstructed image obtained by the nominal value and the theoretical value. So the spherical reference wave has higher precision to the measurement results. Both kinds of reference wave are within the scope of the theoretical depth of focus. So the quality of the reconstructed images which are calculated with measured values, the nominal values and the theoretical calculating values is about the same. The study provides guidance for measurement of lens focal length and wavefront reconstruction of digital holography.
In order to study influence of the surface shape of reference wave on lens focal length, digital holography method was used for theoretical analysis and experimental verification. Focal length was measured respectively with planar reference wave and spherical reference wave at different wavelengths. And then, the measured values were compared with the nominal values and the theoretical calculation values. The results show that the relative errors are above 5% between the measured value, the nominal value and the theoretical calculation value with planar reference wave. The relative errors are blow 2% with spherical reference wave. Therefore, the precision of focal length measured by spherical reference wave is higher. After calculation, focal lengths measured by two different reference lights are within the range of theoretical depth of focal. Therefore, the reconstructed image obtained by the measured value is equivalent to the reconstructed image obtained by the nominal value and the theoretical value. So the spherical reference wave has higher precision to the measurement results. Both kinds of reference wave are within the scope of the theoretical depth of focus. So the quality of the reconstructed images which are calculated with measured values, the nominal values and the theoretical calculating values is about the same. The study provides guidance for measurement of lens focal length and wavefront reconstruction of digital holography.
2017, 41(3): 427-432.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.024
Abstract:
In order to get the damage features of nanosecond laser pulse width to aluminium and provided the basis for choosing proper pulse width in the processing of metals by nanosecond laser, by using the area calculation method and instruments (optical microscope, scanning electron microscope and surface profiler), the damage thresholds of 37 kinds of nanosecond laser (pulse width of 10ns~520ns, wavelength of 1064nm) on aluminium were obtained. The effects of laser pulse number on damage thresholds of aluminium were analyzed with constant pulse width. The function mechanism of nanosecond laser pulse width on the quality of drilling holes in aluminium was also revealed. The results show that the damage threshold of single pulse is linearly related to the square root of laser pulse width of nanosecond laser. The damage threshold of aluminium decreases with the increase of the number of pulse width. The narrower the pulse width of nanosecond laser is, the higher the damage threshold to aluminium is. Evaporation process occupies the leading position during the drilling process. Furthermore, the less the melted thing on the inner wall of hole is, the better the circular degree of hole will be. The less the spraying materials in the orifice is, the higher the quality of drilling will be. The results provide the guide for choosing proper pulse width in the processing of metals with nanosecond laser.
In order to get the damage features of nanosecond laser pulse width to aluminium and provided the basis for choosing proper pulse width in the processing of metals by nanosecond laser, by using the area calculation method and instruments (optical microscope, scanning electron microscope and surface profiler), the damage thresholds of 37 kinds of nanosecond laser (pulse width of 10ns~520ns, wavelength of 1064nm) on aluminium were obtained. The effects of laser pulse number on damage thresholds of aluminium were analyzed with constant pulse width. The function mechanism of nanosecond laser pulse width on the quality of drilling holes in aluminium was also revealed. The results show that the damage threshold of single pulse is linearly related to the square root of laser pulse width of nanosecond laser. The damage threshold of aluminium decreases with the increase of the number of pulse width. The narrower the pulse width of nanosecond laser is, the higher the damage threshold to aluminium is. Evaporation process occupies the leading position during the drilling process. Furthermore, the less the melted thing on the inner wall of hole is, the better the circular degree of hole will be. The less the spraying materials in the orifice is, the higher the quality of drilling will be. The results provide the guide for choosing proper pulse width in the processing of metals with nanosecond laser.
2017, 41(3): 433-437.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.025
Abstract:
In order to study interaction process and damage mechanism between laser and CCD sensors, an interline transfer surface array CCD irradiated by 1.06μm CW laser was analyzed and simulated by means of finite element analysis. Thermal coupling model was established by using laser irradiation area of substrate Si surface as heat source. The temperature distribution and thermal stress distribution of CCD were simulated. By comparing and analyzing temperature damage and stress damage of the components, it was found that stress damage was prior to temperature damage. The results show that as the convergence of the fixed boundary and the free boundary, the thermal stress at the edge of the lower surface of the base Si is the first to exceed the damage threshold of 120MPa at the time of laser action of 0.1s, and stress failure occurs. Si material slips from the lower surface edge to the center, and the substrate is gradually out of fix. At the time of laser action of 0.3s, stress failure occurs to Al film and SiO2 film and Al film strips radically from the inside to the outside due to thermal stress over the adhesion strength of 100MPa, finally the CCD is out of work position and fails. The research achievements provide theoretical basis for laser damage and protection of CCD sensors.
In order to study interaction process and damage mechanism between laser and CCD sensors, an interline transfer surface array CCD irradiated by 1.06μm CW laser was analyzed and simulated by means of finite element analysis. Thermal coupling model was established by using laser irradiation area of substrate Si surface as heat source. The temperature distribution and thermal stress distribution of CCD were simulated. By comparing and analyzing temperature damage and stress damage of the components, it was found that stress damage was prior to temperature damage. The results show that as the convergence of the fixed boundary and the free boundary, the thermal stress at the edge of the lower surface of the base Si is the first to exceed the damage threshold of 120MPa at the time of laser action of 0.1s, and stress failure occurs. Si material slips from the lower surface edge to the center, and the substrate is gradually out of fix. At the time of laser action of 0.3s, stress failure occurs to Al film and SiO2 film and Al film strips radically from the inside to the outside due to thermal stress over the adhesion strength of 100MPa, finally the CCD is out of work position and fails. The research achievements provide theoretical basis for laser damage and protection of CCD sensors.
2017, 41(3): 438-441.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.026
Abstract:
In order to further clarify the influence of pulverized coal particle size on the laser-induced plasma flow characteristics in the process of detecting the composition of pulverized coal by using laser induced breakdown spectroscopy, the screw feeder was used to build coal particle flow detection platform. Spectral datas of 6 kinds of pulverized coal flow plasmas with different particle sizes were analyzed. Under the same experimental conditions, the electron density and temperature of plasma would increase with the decrease of coal particle size. The electron density and temperature of plasma were increased by 19.89% and 13.13% respectively when the sample sizes were < 50μm and 250μm~300μm correspondingly. The results show that, the particle size of pulverized coal has a great influence on the plasma characteristics of laser induced pulverized coal flow. Choosing the appropriate size of pulverized coal can not only improve the spectral intensity but also improve the elements detection limit. It is more favorable for the detection of the low content of elements in the sample.
In order to further clarify the influence of pulverized coal particle size on the laser-induced plasma flow characteristics in the process of detecting the composition of pulverized coal by using laser induced breakdown spectroscopy, the screw feeder was used to build coal particle flow detection platform. Spectral datas of 6 kinds of pulverized coal flow plasmas with different particle sizes were analyzed. Under the same experimental conditions, the electron density and temperature of plasma would increase with the decrease of coal particle size. The electron density and temperature of plasma were increased by 19.89% and 13.13% respectively when the sample sizes were < 50μm and 250μm~300μm correspondingly. The results show that, the particle size of pulverized coal has a great influence on the plasma characteristics of laser induced pulverized coal flow. Choosing the appropriate size of pulverized coal can not only improve the spectral intensity but also improve the elements detection limit. It is more favorable for the detection of the low content of elements in the sample.
2017, 41(3): 442-446.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.027
Abstract:
In order to study the water flow characteristics of target layer during the water assisted laser processing, fluid dynamics analysis software FLUENT was used to do the model and simulation of three different flow devices for water assisted laser processing. The velocity field of fluid above target material was analyzed and the results were analyzed in contrast. The results show that, flow field has difference with the difference of device structure based on the analysis of speed-position curves perpendicular to target material. The fluid speed is smooth within the position of less than 1cm above target. The position is good for laser transmission, slag discharge and processing material placement. The study provides a theory basis for building water flow control device of water assisted laser processing.
In order to study the water flow characteristics of target layer during the water assisted laser processing, fluid dynamics analysis software FLUENT was used to do the model and simulation of three different flow devices for water assisted laser processing. The velocity field of fluid above target material was analyzed and the results were analyzed in contrast. The results show that, flow field has difference with the difference of device structure based on the analysis of speed-position curves perpendicular to target material. The fluid speed is smooth within the position of less than 1cm above target. The position is good for laser transmission, slag discharge and processing material placement. The study provides a theory basis for building water flow control device of water assisted laser processing.
2017, 41(3): 447-450.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.028
Abstract:
In order to handle the difficulty in generating Laguerre-Gaussian mode, the binary amplitude hologram method based on spatial light modulator was presented to produce Laguerre-Gaussian beam. After theoretical analysis and experimental verification, the transfer function of Fourier transform from Gaussian beam to Laguerre-Gaussian beam was derived. Binary hologram which can be used in spatial light modulator was obtained after modifing Laguerre-Gaussian mode simulation. Experimental platform based on 4f system was setup and Laguerre-Gaussian modes of different orders were observed and tested. The results show that, it is easy to build and operate the device conveniently and the device can realize beam output dynamically and controllably. The study is important for the generation of high-order vortex beams and Ince-Gaussian model.
In order to handle the difficulty in generating Laguerre-Gaussian mode, the binary amplitude hologram method based on spatial light modulator was presented to produce Laguerre-Gaussian beam. After theoretical analysis and experimental verification, the transfer function of Fourier transform from Gaussian beam to Laguerre-Gaussian beam was derived. Binary hologram which can be used in spatial light modulator was obtained after modifing Laguerre-Gaussian mode simulation. Experimental platform based on 4f system was setup and Laguerre-Gaussian modes of different orders were observed and tested. The results show that, it is easy to build and operate the device conveniently and the device can realize beam output dynamically and controllably. The study is important for the generation of high-order vortex beams and Ince-Gaussian model.
2017, 41(3): 451-455.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.029
Abstract:
In order to study the transmission characteristics of vortex beams in atmospheric turbulence, based on the generalized Huygens-Fresnel principle, the transmission process of Bessel-Gaussian beams (BGB) in atmospheric turbulence was analyzed theoretically and simulated numerically by using power spectrum inversion method based on fast Fourier transform. Harmonic compensation method was used to generate random phase screen to simulate atmospheric turbulence, which solved the problem that low frequency components were not enough. The results show that, besides turbulence strength, transmission distance, topological charge number and laser wavelength also become the main factors that could affect the vortex beam's communication quality. With the increasing of turbulence strength, the annular intensity decreases, phase distortion becomes more serious, intensity fluctuation is more obvious and beam will gradually degenerate into ordinary Gaussian beam. With the increase of transmission distance, vortex beam has the significant broadening and finally degrades into ordinary Gaussian beam. The longer the laser wavelength is, the stronger the ability which vortex beams restrain turbulence, the stronger annular light intensity is. In the meanwhile, the degree of phase distortion becomes weaker. The smaller topological charge number is, the weaker phase distortion is, and vortex beam would degenerate into ordinary Gaussian beams more easily. The results are helpful for the study of the propagation of vortex beams in free space optical communication.
In order to study the transmission characteristics of vortex beams in atmospheric turbulence, based on the generalized Huygens-Fresnel principle, the transmission process of Bessel-Gaussian beams (BGB) in atmospheric turbulence was analyzed theoretically and simulated numerically by using power spectrum inversion method based on fast Fourier transform. Harmonic compensation method was used to generate random phase screen to simulate atmospheric turbulence, which solved the problem that low frequency components were not enough. The results show that, besides turbulence strength, transmission distance, topological charge number and laser wavelength also become the main factors that could affect the vortex beam's communication quality. With the increasing of turbulence strength, the annular intensity decreases, phase distortion becomes more serious, intensity fluctuation is more obvious and beam will gradually degenerate into ordinary Gaussian beam. With the increase of transmission distance, vortex beam has the significant broadening and finally degrades into ordinary Gaussian beam. The longer the laser wavelength is, the stronger the ability which vortex beams restrain turbulence, the stronger annular light intensity is. In the meanwhile, the degree of phase distortion becomes weaker. The smaller topological charge number is, the weaker phase distortion is, and vortex beam would degenerate into ordinary Gaussian beams more easily. The results are helpful for the study of the propagation of vortex beams in free space optical communication.
2017, 41(3): 456-462.
doi: 10.7510/jgjs.issn.1001-3806.2017.03.030
Abstract:
Femtosecond time-resolved mass spectrometry is the combination of femtosecond pump-probe technique and flight time mass spectrometry. By the technology, ion mass spectra from ionization or dissociation of the molecules excited state can be measured under different pump-probe time delays. The temporal information of the population of the excited states varies with the change of the strength of mass spectra. Some information is given, such as:the accurate lifetime of the excited state and Rydberg state, coupling information of potential energy surface and non adiabatic of molecular excited state, and excessive state information. The application of femtosecond time-resolved mass spectrometry in ultrafast dynamics process is introduced, such as:recent advances of molecular excited states and the latest progress of Rydberg state for dissociation, isomerization, conversion, and system cross. And it is pointed out that femtosecond time-resolved mass spectrometry will play an important role in the study of some new phenomena.
Femtosecond time-resolved mass spectrometry is the combination of femtosecond pump-probe technique and flight time mass spectrometry. By the technology, ion mass spectra from ionization or dissociation of the molecules excited state can be measured under different pump-probe time delays. The temporal information of the population of the excited states varies with the change of the strength of mass spectra. Some information is given, such as:the accurate lifetime of the excited state and Rydberg state, coupling information of potential energy surface and non adiabatic of molecular excited state, and excessive state information. The application of femtosecond time-resolved mass spectrometry in ultrafast dynamics process is introduced, such as:recent advances of molecular excited states and the latest progress of Rydberg state for dissociation, isomerization, conversion, and system cross. And it is pointed out that femtosecond time-resolved mass spectrometry will play an important role in the study of some new phenomena.
