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RSS2018 Vol. 42, No. 1
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[Abstract]
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2018, 42(1): 1-4.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.001
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Abstract:
In order to monitor polarization mode dispersion (PMD) of the fiber communication channel in a pulse position modulation (PPM) transmission system dynamically, a novel PMD monitoring method was proposed based on single sideband polarization phase difference detection technology, and the mathematical model of the method was built in accordance with monitoring principle. The structure of the method was simple, so it can be realized easily at very low cost. The simulation results indicate that the method can realize dynamic PMD monitoring including differential group delay (DGD) and polarization state of output light, and the technique can monitor DGD accurately in the range of 0ps to 100ps. It is proved that the operation of proposed PMD monitor method is independent of data rates, which shows the proposed method can satisfy the need of real time PMD monitoring for PPM transmission systems. It indicates that the proposed method is feasible and effective for PMD monitoring.
In order to monitor polarization mode dispersion (PMD) of the fiber communication channel in a pulse position modulation (PPM) transmission system dynamically, a novel PMD monitoring method was proposed based on single sideband polarization phase difference detection technology, and the mathematical model of the method was built in accordance with monitoring principle. The structure of the method was simple, so it can be realized easily at very low cost. The simulation results indicate that the method can realize dynamic PMD monitoring including differential group delay (DGD) and polarization state of output light, and the technique can monitor DGD accurately in the range of 0ps to 100ps. It is proved that the operation of proposed PMD monitor method is independent of data rates, which shows the proposed method can satisfy the need of real time PMD monitoring for PPM transmission systems. It indicates that the proposed method is feasible and effective for PMD monitoring.
2018, 42(1): 5-10.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.002
Abstract:
In order to improve laser drilling velocity and the utilization of laser energy, the optimal matching parameters of the combined laser drilling were studied by means of space superposition drilling by long-pulse laser and short-pulse laser. The optimal matching model of the combined laser drilling was established. Based on the balance of generation and expulsion of the melted metal, the optimal parameters of long-pulse laser and short-pulse laser, and the combined laser drilling velocity at the optimum matching point were obtained theoretically. The combined laser drilling of stainless steel with the thickness of 5mm was performed with ms and ns pulse Nd:YAG lasers. The experimental results show that in the case of the optimum matching, the combined laser drilling velocity is 3.3 times higher than that of the ms pulse laser alone. Both theory and experiments indicate that the maximum drilling velocity can be obtained at the optimum matching point, and laser energy is fully utilized.
In order to improve laser drilling velocity and the utilization of laser energy, the optimal matching parameters of the combined laser drilling were studied by means of space superposition drilling by long-pulse laser and short-pulse laser. The optimal matching model of the combined laser drilling was established. Based on the balance of generation and expulsion of the melted metal, the optimal parameters of long-pulse laser and short-pulse laser, and the combined laser drilling velocity at the optimum matching point were obtained theoretically. The combined laser drilling of stainless steel with the thickness of 5mm was performed with ms and ns pulse Nd:YAG lasers. The experimental results show that in the case of the optimum matching, the combined laser drilling velocity is 3.3 times higher than that of the ms pulse laser alone. Both theory and experiments indicate that the maximum drilling velocity can be obtained at the optimum matching point, and laser energy is fully utilized.
2018, 42(1): 11-18.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.003
Abstract:
Polymer fiber gratings have many advantages, such as small size, light weight, softness and low cost. Due to the characteristics of polymer itself, it also has high sensitivity, wide response range and good biocompatibility. Firstly, the photosensitivity mechanism of polymer optical fiber was studied, and the etched light source and method for preparing polymer fiber gratings were summarized. Secondly, according to the composition material of polymer optical fiber, the progress in preparation and the performance of polymer fiber gratings, including polymethyl methacrylate, TOPAS, CYTOP and poly-carbonate were overviewed. At present, the study on polymethyl methacrylate polymer fiber gratings is dominant. Polymer fiber gratings based on new materials have been paid more and more attention due to their unique advantages.
Polymer fiber gratings have many advantages, such as small size, light weight, softness and low cost. Due to the characteristics of polymer itself, it also has high sensitivity, wide response range and good biocompatibility. Firstly, the photosensitivity mechanism of polymer optical fiber was studied, and the etched light source and method for preparing polymer fiber gratings were summarized. Secondly, according to the composition material of polymer optical fiber, the progress in preparation and the performance of polymer fiber gratings, including polymethyl methacrylate, TOPAS, CYTOP and poly-carbonate were overviewed. At present, the study on polymethyl methacrylate polymer fiber gratings is dominant. Polymer fiber gratings based on new materials have been paid more and more attention due to their unique advantages.
2018, 42(1): 19-23.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.004
Abstract:
In order to save calcite crystal material and realize rectangular beam splitting of the polarized prism optical path, a calcite-BaF2 ultraviolet rectangular beam splitting polarizing prism was designed by combining calcite and barium fluoride crystal. Ultraviolet light at the wavelength of 265.6nm was chosen as design example. The relationships of splitting angle of e Light and o light, splitting intensity ratio, incident angle and the wavelength of incident light, after incident light passing through the polarizing prism, were analyzed theoretically. And the relationship curve was drawn by the computing software. The results show that the splitting angle and right angle of the polarized prism is small. Light intensity splitting ratio of e light and o light is about 1:1. In the wavelength range of 240nm~400nm, the deviation of right angle beam splitting is less than 1.0° and the deviation of light intensity splitting ratio and 1 is less than 0.02. The prism has a wide light spectrum scope of application. The research provides an important and valuable reference to design, manufacture and application of rectangular beam splitting prisms.
In order to save calcite crystal material and realize rectangular beam splitting of the polarized prism optical path, a calcite-BaF2 ultraviolet rectangular beam splitting polarizing prism was designed by combining calcite and barium fluoride crystal. Ultraviolet light at the wavelength of 265.6nm was chosen as design example. The relationships of splitting angle of e Light and o light, splitting intensity ratio, incident angle and the wavelength of incident light, after incident light passing through the polarizing prism, were analyzed theoretically. And the relationship curve was drawn by the computing software. The results show that the splitting angle and right angle of the polarized prism is small. Light intensity splitting ratio of e light and o light is about 1:1. In the wavelength range of 240nm~400nm, the deviation of right angle beam splitting is less than 1.0° and the deviation of light intensity splitting ratio and 1 is less than 0.02. The prism has a wide light spectrum scope of application. The research provides an important and valuable reference to design, manufacture and application of rectangular beam splitting prisms.
2018, 42(1): 24-29.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.005
Abstract:
In order to study influence of direct metal laser deposition process parameters on the process efficiency, a self-developed HCX60 five-axis laser composite manufacturing center was adopted to carry out Taguchi experiment for process efficiency. Signal-to-noise ratio analysis, range analysis and variance analysis were used to analyze the results. The influence of laser power, powder feed rate, scanning rate, lifting capacity and overlap ratio on process energy efficiency was discussed and the optimum combination of technological factors was put forward. The results show that, powder feeding rate is the most significant parameter for the process of energy efficiency. The best combination of parameters is laser power P of 500W, powder feeding rate f of 28g/min, scanning speed v of 600mm/min, lifting capacity h of 0.6mm and overlap rate λ of 30%. The research provides theoretical and experimental grounds for further studying the effect of process parameters on process energy efficiency and its influence rule.
In order to study influence of direct metal laser deposition process parameters on the process efficiency, a self-developed HCX60 five-axis laser composite manufacturing center was adopted to carry out Taguchi experiment for process efficiency. Signal-to-noise ratio analysis, range analysis and variance analysis were used to analyze the results. The influence of laser power, powder feed rate, scanning rate, lifting capacity and overlap ratio on process energy efficiency was discussed and the optimum combination of technological factors was put forward. The results show that, powder feeding rate is the most significant parameter for the process of energy efficiency. The best combination of parameters is laser power P of 500W, powder feeding rate f of 28g/min, scanning speed v of 600mm/min, lifting capacity h of 0.6mm and overlap rate λ of 30%. The research provides theoretical and experimental grounds for further studying the effect of process parameters on process energy efficiency and its influence rule.
2018, 42(1): 30-33.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.006
Abstract:
In order to detect the long rail straightness, laser was used as the reference line, and 2-D position sensitive detector was used as photoelectric converter. When 2-D position sensitive detector was fixed on the guide rail slider and moved along the guide rail, the spot position data was transmitted to the terminal through bluetooth module. After entering the location information, the curve of 2-D straightness was drawn by the software automatically. The results show that, through theoretical analysis, the error of laser deflection angle is calculated and is less than 1μm. The system accuracy is verified by high-precision displacement platform experiment and reaches 3.4μm. In practical appliaction, a long rail of 7.2m is detected and the straightness data of long guide rail is obtained. The repeatability precision can reach 5μm. The study is helpful for straightness measurement of long rails.
In order to detect the long rail straightness, laser was used as the reference line, and 2-D position sensitive detector was used as photoelectric converter. When 2-D position sensitive detector was fixed on the guide rail slider and moved along the guide rail, the spot position data was transmitted to the terminal through bluetooth module. After entering the location information, the curve of 2-D straightness was drawn by the software automatically. The results show that, through theoretical analysis, the error of laser deflection angle is calculated and is less than 1μm. The system accuracy is verified by high-precision displacement platform experiment and reaches 3.4μm. In practical appliaction, a long rail of 7.2m is detected and the straightness data of long guide rail is obtained. The repeatability precision can reach 5μm. The study is helpful for straightness measurement of long rails.
2018, 42(1): 34-38.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.007
Abstract:
In order to achieve laser output with high repetition rate, short pulse duration and high beam quality, a LD pumped acousto-optically Q-switched Nd:YVO4 solid-state laser was designed and set up. In the lasing experiments, the seed laser with an excellent beam quality was obtained from the master oscillator. The parameters of the seed laser are 25kHz repetition, 22.4μJ pulse energy, 2.19ns pulse duration, 24.3% optical-to-optical conversion. efficiency and M2 < 1.2. The output laser from the power amplifier is with 25kHz repetition, 585μJ pulse energy, 2.26ns pulse duration, 15.6% extraction efficiency and M2 < 1.7. The result shows that laser output with high repetition rate, short pulse duration and high beam quality could be achieved by LD pumped acousto-optically Q-switched Nd:YVO4 lasers and the experimental results are almost in accordance with the theoretical calculation results.
In order to achieve laser output with high repetition rate, short pulse duration and high beam quality, a LD pumped acousto-optically Q-switched Nd:YVO4 solid-state laser was designed and set up. In the lasing experiments, the seed laser with an excellent beam quality was obtained from the master oscillator. The parameters of the seed laser are 25kHz repetition, 22.4μJ pulse energy, 2.19ns pulse duration, 24.3% optical-to-optical conversion. efficiency and M2 < 1.2. The output laser from the power amplifier is with 25kHz repetition, 585μJ pulse energy, 2.26ns pulse duration, 15.6% extraction efficiency and M2 < 1.7. The result shows that laser output with high repetition rate, short pulse duration and high beam quality could be achieved by LD pumped acousto-optically Q-switched Nd:YVO4 lasers and the experimental results are almost in accordance with the theoretical calculation results.
2018, 42(1): 39-42.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.008
Abstract:
In order to study the damage mechanism and influencing factors of laser thin films, the principle of radiation measurement based on flat top beam was proposed. The cumulative damage effect of HfO2 films processed by electron beam thermal evaporation under the repeated frequency laser irradiation was studied by using 1064nm Nd:YAG laser. After theoretical analysis and experimental verification, the characteristics of two measuring methods, 1-on-1 and S-on-1, were analyzed based on the measuring principle of damage threshold. The irradiation laser energy was seeked by dichotomy. Each energy density was irradiated at 20 test points. Zero probability damage threshold and least square method were used to fit and determine the measurement results. The results show that for the same kind of film, the damage threshold measured by 1-on-1 method is 15.75J/cm2 and the damage threshold measured by S-on-1 method is 11.90J/cm2. The comparison of damage threshold and damage morphology shows that S-on-1 measurement method reflects the typical cumulative effect. The study is of great importance for the study of laser damage mechanism and influencing factors of thin film.
In order to study the damage mechanism and influencing factors of laser thin films, the principle of radiation measurement based on flat top beam was proposed. The cumulative damage effect of HfO2 films processed by electron beam thermal evaporation under the repeated frequency laser irradiation was studied by using 1064nm Nd:YAG laser. After theoretical analysis and experimental verification, the characteristics of two measuring methods, 1-on-1 and S-on-1, were analyzed based on the measuring principle of damage threshold. The irradiation laser energy was seeked by dichotomy. Each energy density was irradiated at 20 test points. Zero probability damage threshold and least square method were used to fit and determine the measurement results. The results show that for the same kind of film, the damage threshold measured by 1-on-1 method is 15.75J/cm2 and the damage threshold measured by S-on-1 method is 11.90J/cm2. The comparison of damage threshold and damage morphology shows that S-on-1 measurement method reflects the typical cumulative effect. The study is of great importance for the study of laser damage mechanism and influencing factors of thin film.
2018, 42(1): 43-47.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.009
Abstract:
In order to obtain simple and compact solid-state lasers, a LD end-pumped slab laser with a folded three-pass resonator was used and its thermal lens equivalent cavity model was established. The equivalent cavity stability and cavity mode radius were simulated and analyzed. The new structure and flat cavity structure were studied comparatively based on experiments. The results show that, when the length of the folded three-pass cavity is 170mm, the power output of 1064nm laser is 21W, light-light efficiency is 16.4%, slope efficiency is 25%, and M2 factors in horizontal and vertical directions are 10.8 and 2.76 respectively. Under the same conditions, M2 factor in horizontal direction is improved from 152.7 of the parallel-plane resonator to 10.8 of the folded three-pass cavity. The horizontal direction of output spot is compressed from 10.8mm of the parallel-flat cavity to 4.1mm of the folded three-pass cavity. Beam output capability of the simple and compact end-pumped laser with a folded three-pass resonator is verified. The study is of practical significance for obtaining intracavity Q-switched and intracavity frequency-doubled 532nm lasers.
In order to obtain simple and compact solid-state lasers, a LD end-pumped slab laser with a folded three-pass resonator was used and its thermal lens equivalent cavity model was established. The equivalent cavity stability and cavity mode radius were simulated and analyzed. The new structure and flat cavity structure were studied comparatively based on experiments. The results show that, when the length of the folded three-pass cavity is 170mm, the power output of 1064nm laser is 21W, light-light efficiency is 16.4%, slope efficiency is 25%, and M2 factors in horizontal and vertical directions are 10.8 and 2.76 respectively. Under the same conditions, M2 factor in horizontal direction is improved from 152.7 of the parallel-plane resonator to 10.8 of the folded three-pass cavity. The horizontal direction of output spot is compressed from 10.8mm of the parallel-flat cavity to 4.1mm of the folded three-pass cavity. Beam output capability of the simple and compact end-pumped laser with a folded three-pass resonator is verified. The study is of practical significance for obtaining intracavity Q-switched and intracavity frequency-doubled 532nm lasers.
2018, 42(1): 48-52.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.010
Abstract:
In order to obtain photonic crystal fibers with good dispersion characteristics, by the finite element method, the theoretical analysis and experimental verification were carried out, and the effective index of refraction and dispersion coefficient with the change of wavelength were obtained. According to the analysis results, when the hole diameter d=1.6μm and the hole spacing Λ=2μm, the dispersion flatness is better in the 1.2μm~2.1μm band and the dispersion coefficient is 108.20ps/(nm·km) at the wavelength of 1550nm. Based on this structure, effect of different filling modes and filling material on the dispersion characteristics was studied. The results show that better dispersion characteristics are obtained for the "十" shape filling method, and that when ordinary alcohol is used as filling material, the dispersion coefficient at the wavelength of 1550nm can be reduced to 20.39ps/(nm·km), which is close to that of a G.652 single mode fiber at 1550nm. This result is helpful for research in the optical communication field.
In order to obtain photonic crystal fibers with good dispersion characteristics, by the finite element method, the theoretical analysis and experimental verification were carried out, and the effective index of refraction and dispersion coefficient with the change of wavelength were obtained. According to the analysis results, when the hole diameter d=1.6μm and the hole spacing Λ=2μm, the dispersion flatness is better in the 1.2μm~2.1μm band and the dispersion coefficient is 108.20ps/(nm·km) at the wavelength of 1550nm. Based on this structure, effect of different filling modes and filling material on the dispersion characteristics was studied. The results show that better dispersion characteristics are obtained for the "十" shape filling method, and that when ordinary alcohol is used as filling material, the dispersion coefficient at the wavelength of 1550nm can be reduced to 20.39ps/(nm·km), which is close to that of a G.652 single mode fiber at 1550nm. This result is helpful for research in the optical communication field.
2018, 42(1): 53-59.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.011
Abstract:
In order to avoid defects such as overburning and collapsing at the boundary of laser cladding layer, difference of heat dissipation at different positions of the substrate was analyzed based on the theory of heat conduction. The influence of scanning path on temperature distribution was studied by numerical calculation. With the parameters of laser power 1000W, scanning speed 5mm/s, powder feeding quantity 9.15g/min, scanning interval 1.5mm and substrate size 40mm×30mm×7mm, molten pool temperature of boundary under the same direction cladding and different side cladding is about 300℃ and 500℃ lower than that under different direction cladding and the same side cladding respectively. Overburning and collapsing regions under different direction cladding and the same side cladding are predicted and experimentally verified. The results show that the scanning path has a great influence on the overburning and collapsing of boundary. The same direction cladding and different side cladding can improve the cladding quality of boundary without changing machining efficiency, material utilization ratio and the rationality of process parameters. Different side cladding can balance the relationship between heat accumulation and heat dissipation better, which can refine the grain of boundary, make internal microstructure uniform and increase the performance of cladding layer. This study is helpful to improve the quality of laser cladding layer.
In order to avoid defects such as overburning and collapsing at the boundary of laser cladding layer, difference of heat dissipation at different positions of the substrate was analyzed based on the theory of heat conduction. The influence of scanning path on temperature distribution was studied by numerical calculation. With the parameters of laser power 1000W, scanning speed 5mm/s, powder feeding quantity 9.15g/min, scanning interval 1.5mm and substrate size 40mm×30mm×7mm, molten pool temperature of boundary under the same direction cladding and different side cladding is about 300℃ and 500℃ lower than that under different direction cladding and the same side cladding respectively. Overburning and collapsing regions under different direction cladding and the same side cladding are predicted and experimentally verified. The results show that the scanning path has a great influence on the overburning and collapsing of boundary. The same direction cladding and different side cladding can improve the cladding quality of boundary without changing machining efficiency, material utilization ratio and the rationality of process parameters. Different side cladding can balance the relationship between heat accumulation and heat dissipation better, which can refine the grain of boundary, make internal microstructure uniform and increase the performance of cladding layer. This study is helpful to improve the quality of laser cladding layer.
2018, 42(1): 60-65.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.012
Abstract:
In order to explore spatial distribution characteristics of diffusion flame, spatially-resolved laser-induced breakdown spectroscopy (LIBS) was used to study the laminar diffusion methane-air flame. The spatial distributions of the threshold energy, the plasma energy and the intensity ratio were obtained at different heights (7mm, 9mm and 11mm) with the flow rate of 0.100L/min and 0.120L/min. The results show that the spatial distribution of flame temperature can be qualitatively described by the plasma energy. Combining the analysis of the plasma energy distribution and the H/O intensity ratio distribution, the positions of the flame front and the width of secondary combustion region can be determined. In addition, according to the relevant measurement, the linear equation for H/O intensity ratio and equivalent ratio can be determined approximately. By this linear equation, the axial distribution of local equivalent ratio and the flame length is obtained. These results have important significance for LIBS application in combustion diagnosis.
In order to explore spatial distribution characteristics of diffusion flame, spatially-resolved laser-induced breakdown spectroscopy (LIBS) was used to study the laminar diffusion methane-air flame. The spatial distributions of the threshold energy, the plasma energy and the intensity ratio were obtained at different heights (7mm, 9mm and 11mm) with the flow rate of 0.100L/min and 0.120L/min. The results show that the spatial distribution of flame temperature can be qualitatively described by the plasma energy. Combining the analysis of the plasma energy distribution and the H/O intensity ratio distribution, the positions of the flame front and the width of secondary combustion region can be determined. In addition, according to the relevant measurement, the linear equation for H/O intensity ratio and equivalent ratio can be determined approximately. By this linear equation, the axial distribution of local equivalent ratio and the flame length is obtained. These results have important significance for LIBS application in combustion diagnosis.
2018, 42(1): 66-71.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.013
Abstract:
The design and selection of focusing evaluation function was one of the key problems of automatic focusing microscopes. The illumination change would cause function curve to lose its ideal characteristics. The traditional focusing evaluation function can not overcome this problem. In order to solve the problem, an automatic focusing algorithm combining discrete cosine transform (DCT) coefficient of zero of frequency domain and local standard deviation of spatial domain was proposed. DCT coefficient of zero and local standard deviation of sub-blocks were calculated. Division operation was performed by taking advantage of the opposite effect. And square algorithm was used to increase the clarity ratio of the algorithm. Under different light conditions, compared with several traditional focusing evaluation functions, the focusing experiment was carried out to verify the applicability of the new algorithm. The performance of focus evaluation function was evaluated quantitatively. The results show that the algorithm can keep good curve characteristics under low illumination conditions and has strong anti-noise ability, sensitivity and stability.
The design and selection of focusing evaluation function was one of the key problems of automatic focusing microscopes. The illumination change would cause function curve to lose its ideal characteristics. The traditional focusing evaluation function can not overcome this problem. In order to solve the problem, an automatic focusing algorithm combining discrete cosine transform (DCT) coefficient of zero of frequency domain and local standard deviation of spatial domain was proposed. DCT coefficient of zero and local standard deviation of sub-blocks were calculated. Division operation was performed by taking advantage of the opposite effect. And square algorithm was used to increase the clarity ratio of the algorithm. Under different light conditions, compared with several traditional focusing evaluation functions, the focusing experiment was carried out to verify the applicability of the new algorithm. The performance of focus evaluation function was evaluated quantitatively. The results show that the algorithm can keep good curve characteristics under low illumination conditions and has strong anti-noise ability, sensitivity and stability.
2018, 42(1): 72-77.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.014
Abstract:
In order to analyze the trapping efficiency of multi-layer particles in a focused beam, the T matrix of the double-layer spherical particle was deduced. The trapping force on double-layer spherical particles was numerically calculated by means of the vector diffraction integral combining the T matrix method and the Maxwell stress tensor integral. Effect of the refractive index and size of the inner layer on trapping efficiency was discussed in detail. The focused beam can trap the double-layer spherical particles only when the refractive index of the inner layer is appropriate. The maximum backward trapping efficiency will increase at first and decrease to zero finally when the refractive index increases. For hollow particles, the bigger the hollow is, the weaker the trap is. Besides, the trap formed by plane wave is stronger than Gaussian beam. The calculation method of the force on double-layer spherical particles can be expanded to the case of multilayer complex particles.
In order to analyze the trapping efficiency of multi-layer particles in a focused beam, the T matrix of the double-layer spherical particle was deduced. The trapping force on double-layer spherical particles was numerically calculated by means of the vector diffraction integral combining the T matrix method and the Maxwell stress tensor integral. Effect of the refractive index and size of the inner layer on trapping efficiency was discussed in detail. The focused beam can trap the double-layer spherical particles only when the refractive index of the inner layer is appropriate. The maximum backward trapping efficiency will increase at first and decrease to zero finally when the refractive index increases. For hollow particles, the bigger the hollow is, the weaker the trap is. Besides, the trap formed by plane wave is stronger than Gaussian beam. The calculation method of the force on double-layer spherical particles can be expanded to the case of multilayer complex particles.
2018, 42(1): 78-82.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.015
Abstract:
8-hydroxy quinoline aluminum is an organic semiconductor material and has broad application prospect in the field of solar cell application. In order to study the transport dynamic information of carriers, 8-hydroxyl quinoline aluminum thin film was prepared under the condition of constant temperature. The method of X-ray diffraction was used to analyze the properties of the film and the method of time-of-flight(TOF) was used to study the experimental conditions affecting the carrier mobility by theoretical analysis and experimental verification. The results show that this method is feasible. The carrier transport law of 8-hydroxy quinoline aluminum in the temperature range of 308K~338K is in accordance with shallow trap model. When the sampling resistance is less than 15kΩ and pulse energy is less than 3.5μJ, the carrier TOF remains constant. The test results are reliable. The result is helpful for the preparation of organic solar cells.
8-hydroxy quinoline aluminum is an organic semiconductor material and has broad application prospect in the field of solar cell application. In order to study the transport dynamic information of carriers, 8-hydroxyl quinoline aluminum thin film was prepared under the condition of constant temperature. The method of X-ray diffraction was used to analyze the properties of the film and the method of time-of-flight(TOF) was used to study the experimental conditions affecting the carrier mobility by theoretical analysis and experimental verification. The results show that this method is feasible. The carrier transport law of 8-hydroxy quinoline aluminum in the temperature range of 308K~338K is in accordance with shallow trap model. When the sampling resistance is less than 15kΩ and pulse energy is less than 3.5μJ, the carrier TOF remains constant. The test results are reliable. The result is helpful for the preparation of organic solar cells.
2018, 42(1): 83-88.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.016
Abstract:
In order to study high performance filters based on photonic crystal waveguide, some methods such as adjusting the structures of resonant cavities and optimizing the coupling regions were adopted in the paper. Three kinds of bent photonic crystal waveguides were designed based on the coupled-mode theory in square dielectric rod photonic crystal. After theoretical analysis and experimental verification, the performance characteristics in the S-band and C-band were studied by the time-domain finite-different method. The results show that, 3 kinds of waveguides have good band stop or band pass characteristics at different wavelengths. Cutoff transmission wavelength and passband transmission wavelength shift toward longer wavelengths with the increase of relative dielectric constant of the overall dielectric column. Cutoff wavelength and transmission wavelength are increased by about 6nm with the increase of dielectric constant εr by 0.3. The study has potential value in the designs of micro optical sensors, micro optical communication devices, optical integrated circuits, etc.
In order to study high performance filters based on photonic crystal waveguide, some methods such as adjusting the structures of resonant cavities and optimizing the coupling regions were adopted in the paper. Three kinds of bent photonic crystal waveguides were designed based on the coupled-mode theory in square dielectric rod photonic crystal. After theoretical analysis and experimental verification, the performance characteristics in the S-band and C-band were studied by the time-domain finite-different method. The results show that, 3 kinds of waveguides have good band stop or band pass characteristics at different wavelengths. Cutoff transmission wavelength and passband transmission wavelength shift toward longer wavelengths with the increase of relative dielectric constant of the overall dielectric column. Cutoff wavelength and transmission wavelength are increased by about 6nm with the increase of dielectric constant εr by 0.3. The study has potential value in the designs of micro optical sensors, micro optical communication devices, optical integrated circuits, etc.
2018, 42(1): 89-93.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.017
Abstract:
In order to reduce the influence of noise and interference on the detection accuracy of optical spot coordinates in semi-active laser weapons, the measurement bandwidth of pulse signal increased and the effective value of the signal was extracted. By overcoming the great time-consuming and complexity of the serial fast Fourier transform (FFT) operation, parallel FFT computing method was proposed based on multi-core and parallel architecture system on chip-field-programmable gate array (SoC-FPGA) platform and OpenCL software. By this method, the time complexity of FFT (1-D) can be reduced to 1/Q times and the better acceleration effect was obtained. After comparing the computational time-consuming experiments of three platforms (advanced risc machines, digital signal processing and SoC-FPGA), the caculating time of the proposed algorithm is to 6.0449ms (1-D 4096 points) and less than that of the other two platforms with the same number of points. The results show that parallel FFT algorithm not only meets the requirement of the real-time performance of laser semi-active seeker and achieves the effect of denoising, but also can effectively reduce the influence of noise and background light.
In order to reduce the influence of noise and interference on the detection accuracy of optical spot coordinates in semi-active laser weapons, the measurement bandwidth of pulse signal increased and the effective value of the signal was extracted. By overcoming the great time-consuming and complexity of the serial fast Fourier transform (FFT) operation, parallel FFT computing method was proposed based on multi-core and parallel architecture system on chip-field-programmable gate array (SoC-FPGA) platform and OpenCL software. By this method, the time complexity of FFT (1-D) can be reduced to 1/Q times and the better acceleration effect was obtained. After comparing the computational time-consuming experiments of three platforms (advanced risc machines, digital signal processing and SoC-FPGA), the caculating time of the proposed algorithm is to 6.0449ms (1-D 4096 points) and less than that of the other two platforms with the same number of points. The results show that parallel FFT algorithm not only meets the requirement of the real-time performance of laser semi-active seeker and achieves the effect of denoising, but also can effectively reduce the influence of noise and background light.
2018, 42(1): 94-99.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.018
Abstract:
In order to study influence of laser forming methods on forming profile and microstructure, T2 copper foils with thickness of 40μm and 80μm were used to do experiments of laser shock micro bulging and micro deep drawing. At the same time, ABAQUS finite element simulation was used to simulate the experiment, and the displacement and residual stress field of the foil under different deformation modes were studied. The results show that, after bulging, necking occurs in the deformed region of copper foils. The deformation mechanism mainly includes dislocation sliding, deformation distortion grain and mechanical twinning in the laser processed region. The upper surface of the foil (laser shock surface) is residual tensile stress and the maximum value is about 372.3MPa. The lower surface of the foil (the opposite of laser shock surface) is residual compressive stress and the maximum value is about -218.7MPa. For drawing, foil forming profile is smooth and has uniform thickness distribution. A large number of dislocations and mechanical twinning appear in laser processed region. The upper surface of the foil is residual compressive stress and the maximum value is about -365.6MPa. The lower surface of the foil is residual tensile stress and the maximum value is about 203MPa. This result is helpful for the control of laser shock forming of foil.
In order to study influence of laser forming methods on forming profile and microstructure, T2 copper foils with thickness of 40μm and 80μm were used to do experiments of laser shock micro bulging and micro deep drawing. At the same time, ABAQUS finite element simulation was used to simulate the experiment, and the displacement and residual stress field of the foil under different deformation modes were studied. The results show that, after bulging, necking occurs in the deformed region of copper foils. The deformation mechanism mainly includes dislocation sliding, deformation distortion grain and mechanical twinning in the laser processed region. The upper surface of the foil (laser shock surface) is residual tensile stress and the maximum value is about 372.3MPa. The lower surface of the foil (the opposite of laser shock surface) is residual compressive stress and the maximum value is about -218.7MPa. For drawing, foil forming profile is smooth and has uniform thickness distribution. A large number of dislocations and mechanical twinning appear in laser processed region. The upper surface of the foil is residual compressive stress and the maximum value is about -365.6MPa. The lower surface of the foil is residual tensile stress and the maximum value is about 203MPa. This result is helpful for the control of laser shock forming of foil.
2018, 42(1): 100-103.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.019
Abstract:
In order to achieve the ultraviolet pulsed laser with the high power and high frequency, the fourth harmonic 266nm in LiB3O5 (LBO)crystal was generated by frequency mixing of the fundamental(1064nm) and third harmonic (355nm) of electro-optical Q-switched laser, and experiment verification was carried out. Deep ultraviolet (UV) output power of 2.5W at 266nm with the repetition rate at 20kHz and 12.5% infrared(IR)-to-UV conversion efficiency were achieved. The result show that the pulse laser has achieved a large average output power at high repetition frequency by using LBO crystal.
In order to achieve the ultraviolet pulsed laser with the high power and high frequency, the fourth harmonic 266nm in LiB3O5 (LBO)crystal was generated by frequency mixing of the fundamental(1064nm) and third harmonic (355nm) of electro-optical Q-switched laser, and experiment verification was carried out. Deep ultraviolet (UV) output power of 2.5W at 266nm with the repetition rate at 20kHz and 12.5% infrared(IR)-to-UV conversion efficiency were achieved. The result show that the pulse laser has achieved a large average output power at high repetition frequency by using LBO crystal.
2018, 42(1): 104-107.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.020
Abstract:
In order to improvelaser beam quality of unstable cavity high energy laser systems and the utilization of the aperture of a transmitting optical system, a new optical shaping method for the annular beam was proposed. Optical elements were added to the light path outside the laser cavity to shape the output of annular laser beam. On the basis of theoretical analysis, beam shaping devices based on dual axicons were designed and fabricated. The shaping experiments were carried out for the annular beam from an unstable cavity high energy laser. The data was obtained and was consistent with theoretical analysis.The results show that, the beam after shaping by using dual axicons has better beam quality than that of the original beam. Waist diameter decreases from 45mm to 32mm. M2 factor reduces from 14 to 11.8. The method is feasible for the shaping and transformation of the annular beam from an unstable resonator.
In order to improvelaser beam quality of unstable cavity high energy laser systems and the utilization of the aperture of a transmitting optical system, a new optical shaping method for the annular beam was proposed. Optical elements were added to the light path outside the laser cavity to shape the output of annular laser beam. On the basis of theoretical analysis, beam shaping devices based on dual axicons were designed and fabricated. The shaping experiments were carried out for the annular beam from an unstable cavity high energy laser. The data was obtained and was consistent with theoretical analysis.The results show that, the beam after shaping by using dual axicons has better beam quality than that of the original beam. Waist diameter decreases from 45mm to 32mm. M2 factor reduces from 14 to 11.8. The method is feasible for the shaping and transformation of the annular beam from an unstable resonator.
2018, 42(1): 108-112.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.021
Abstract:
In order to study diffraction characteristics of an external cavity diode laser based on dual volume Bragg gratings, a Bragg grating and a transversely chirped Bragg grating were used to compose the dual volume Bragg gratings. The diffraction characteristics of the volume Bragg gratings before and after the combination were analyzed theoretically. The output spectral characteristics of the external cavity diode laser based on dual volume Bragg gratings were studied. The experimental results show that, under the action of the external cavity feedback of the dual volume Bragg gratings, the dual wavelengths can be output simultaneously. By moving the transversely chirped Bragg grating in the lateral direction, it is possible to keep the other one wavelength tuning linearly in the range of 800nm~815nm. This study provides experimental guidance for high-power diode lasers based on dual volume Bragg gratings for dual wavelength output.
In order to study diffraction characteristics of an external cavity diode laser based on dual volume Bragg gratings, a Bragg grating and a transversely chirped Bragg grating were used to compose the dual volume Bragg gratings. The diffraction characteristics of the volume Bragg gratings before and after the combination were analyzed theoretically. The output spectral characteristics of the external cavity diode laser based on dual volume Bragg gratings were studied. The experimental results show that, under the action of the external cavity feedback of the dual volume Bragg gratings, the dual wavelengths can be output simultaneously. By moving the transversely chirped Bragg grating in the lateral direction, it is possible to keep the other one wavelength tuning linearly in the range of 800nm~815nm. This study provides experimental guidance for high-power diode lasers based on dual volume Bragg gratings for dual wavelength output.
2018, 42(1): 113-116.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.022
Abstract:
In order to study the higher order harmonic radiation induced by the interaction between super laser and thin foil targets in the reflection direction of incident light, the spatial distribution of high-order harmonic radiation of ultraintense laser-driven thin foil targets (high-density film targets) was investigated in the transmission and reflection direction of incident laser by using particle simulation method, because synchrotron radiation mechanism could lead to higher harmonic generation in the transmission direction of incident laser. The results show that, when the target thickness is less than the laser skin depth and the target plasma density is much larger than the critical density (800Nc), coherent synchrotron radiation can cause higher order radiation in the transmission direction. Harmonic field radiation is driven by relativistic mirror oscillation mechanism in the reflection direction. During the interaction between ultraintense laser and thin foil target, the coexistence of two harmonic generation mechanisms is proved. The influence of target thickness on the order of harmonic radiation was discussed under two kinds of production mechanism. The transmitted harmonics are more than 65 orders when target thickness exceeds 200nm. The study has some theoretical significance to research of high order harmonics generated by ultraintense laser-driven film targets and the future development of attosecond X-ray light sources.
In order to study the higher order harmonic radiation induced by the interaction between super laser and thin foil targets in the reflection direction of incident light, the spatial distribution of high-order harmonic radiation of ultraintense laser-driven thin foil targets (high-density film targets) was investigated in the transmission and reflection direction of incident laser by using particle simulation method, because synchrotron radiation mechanism could lead to higher harmonic generation in the transmission direction of incident laser. The results show that, when the target thickness is less than the laser skin depth and the target plasma density is much larger than the critical density (800Nc), coherent synchrotron radiation can cause higher order radiation in the transmission direction. Harmonic field radiation is driven by relativistic mirror oscillation mechanism in the reflection direction. During the interaction between ultraintense laser and thin foil target, the coexistence of two harmonic generation mechanisms is proved. The influence of target thickness on the order of harmonic radiation was discussed under two kinds of production mechanism. The transmitted harmonics are more than 65 orders when target thickness exceeds 200nm. The study has some theoretical significance to research of high order harmonics generated by ultraintense laser-driven film targets and the future development of attosecond X-ray light sources.
2018, 42(1): 117-120.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.023
Abstract:
In order to achieve high-degree isolation in a transceiver system, an isolation optical system was put forward based on polarization and analyzed by means of Jones matrix. The feasibility of polarization isolation in a coaxial optical transceiver was verified. The space separation was used to suppress the echo into the receiving system. The influence of the wedge angle of polarization beam splitter on transmitting-receiving isolation was studied. The results show that, the transmitting-receiving isolation of 100dB is achieved with a certain wedge angle. The results will be of guiding significance for the design of transmitting-receiving coaxial optical systems.
In order to achieve high-degree isolation in a transceiver system, an isolation optical system was put forward based on polarization and analyzed by means of Jones matrix. The feasibility of polarization isolation in a coaxial optical transceiver was verified. The space separation was used to suppress the echo into the receiving system. The influence of the wedge angle of polarization beam splitter on transmitting-receiving isolation was studied. The results show that, the transmitting-receiving isolation of 100dB is achieved with a certain wedge angle. The results will be of guiding significance for the design of transmitting-receiving coaxial optical systems.
2018, 42(1): 121-126.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.024
Abstract:
In order to study the interaction of Laguerre-Gaussian beam and fused quartz, the method of simulation calculation was adopted to study the temperature and thermal stress of the fused quartz irradiated by 3 modes of Laguerre-Gaussian beam (TEM00, TEM01, TEM10). The simulation data were obtained. The results show that spatial distribution of laser intensity affects temperature distribution and stress distribution of the materials. The accumulation effect of temperature is obvious. After continuous laser pulse action, the material temperature continues to rise. The focus area is over 1900℃. The temperature gradient leads to thermal stress. The local thermal stress is close to 50MPa. The simulation results provide the useful reference for the processing of fused silica.
In order to study the interaction of Laguerre-Gaussian beam and fused quartz, the method of simulation calculation was adopted to study the temperature and thermal stress of the fused quartz irradiated by 3 modes of Laguerre-Gaussian beam (TEM00, TEM01, TEM10). The simulation data were obtained. The results show that spatial distribution of laser intensity affects temperature distribution and stress distribution of the materials. The accumulation effect of temperature is obvious. After continuous laser pulse action, the material temperature continues to rise. The focus area is over 1900℃. The temperature gradient leads to thermal stress. The local thermal stress is close to 50MPa. The simulation results provide the useful reference for the processing of fused silica.
2018, 42(1): 127-130.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.025
Abstract:
In order to obtain technological parameters for cleaning tire molds with laser, a self-developed pulse YAG laser with the average power of 250W was used to carry out experiment of tire mold cleaning. The experimental data of the relationship between different laser parameters and the cleaning effect of the tire mold was obtained. The relationships between the parameters such as laser peak power, energy density and cleaning speed, cleaning effect of the tire mold were studied. The results show that for cleaning tire molds, pulse YAG laser is more efficient than CO2 laser. Laser energy density threshold for cleaning tire molds is about 250mJ/mm2. The increase of laser peak power and average power can improve cleaning speeds and cleaning effect. The research provides the reference for research of laser cleaning equipment in this field.
In order to obtain technological parameters for cleaning tire molds with laser, a self-developed pulse YAG laser with the average power of 250W was used to carry out experiment of tire mold cleaning. The experimental data of the relationship between different laser parameters and the cleaning effect of the tire mold was obtained. The relationships between the parameters such as laser peak power, energy density and cleaning speed, cleaning effect of the tire mold were studied. The results show that for cleaning tire molds, pulse YAG laser is more efficient than CO2 laser. Laser energy density threshold for cleaning tire molds is about 250mJ/mm2. The increase of laser peak power and average power can improve cleaning speeds and cleaning effect. The research provides the reference for research of laser cleaning equipment in this field.
2018, 42(1): 131-135.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.026
Abstract:
In order to obtain high-performance Ni-Fe-Al alloy from nickel, iron and aluminum elemental powder, based on the molding process of 3-D laser printing for mixed metal powder, a medium-low-power fiber laser was used to study the cladding metallurgy of a certain percentage of nickel, iron and aluminum mixed powder through a series of laser cladding experiments on stainless steel and high temperature nickel-based alloy substrates respectively. During the experiment, the combination of laser parameters (laser frequency, scanning speed, laser power and defocus amount) was optimized and a good single track cladding result was obtained. Its macro-morphology and microstructure were observed by using a laser scanning confocal microscope, a metallographic microscope, a scanning electron microscopy and other means of detection respectively. It is found that, a good alloy without pores and cracks is obtained and a good metallurgical bond is formed with the substrate. The hardness of the cladding layer is 30HV lower than that of the substrate, but the hardness is uniform in the section. The study result is helpful to obtain an isotropic metallurgical layer.
In order to obtain high-performance Ni-Fe-Al alloy from nickel, iron and aluminum elemental powder, based on the molding process of 3-D laser printing for mixed metal powder, a medium-low-power fiber laser was used to study the cladding metallurgy of a certain percentage of nickel, iron and aluminum mixed powder through a series of laser cladding experiments on stainless steel and high temperature nickel-based alloy substrates respectively. During the experiment, the combination of laser parameters (laser frequency, scanning speed, laser power and defocus amount) was optimized and a good single track cladding result was obtained. Its macro-morphology and microstructure were observed by using a laser scanning confocal microscope, a metallographic microscope, a scanning electron microscopy and other means of detection respectively. It is found that, a good alloy without pores and cracks is obtained and a good metallurgical bond is formed with the substrate. The hardness of the cladding layer is 30HV lower than that of the substrate, but the hardness is uniform in the section. The study result is helpful to obtain an isotropic metallurgical layer.
2018, 42(1): 136-140.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.027
Abstract:
In order to study the manufacturing process of laser 3-D printing for automobile engine connecting rods, by means of theoretical analysis and experimental verification, 3-D model of a connecting rod was established and slicing was done. By S-type scanning and contour offset scanning, two machining paths of connecting rods were planned. Alloy powders based on iron and the corresponding technological parameters were selected to carry out the rod print test in a laser 3-D printing system. It took 4min30s~4min56s to scanning a single layer and it took 4h20min totally. The results show that the metallographic structure at the bottom of the forming zone of the connecting rod is mainly columnar crystal and dendritic crystal. The middle and upper part are small equiaxed crystal. Interlayer is dense and good metallurgical bonding had been formed. The microhardness of the formed connecting rod is 450HV~490HV, yield strength is 754MPa, tensile strength is 1189MPa, and elongation rate was 9%. Compared to forging, powder forging manufacturing processes, laser 3-D printing forming reduces tooling costs and shortens the production preparation time. Its mechanical properties, such as yield strength and tensile strength, exceed those of steel forging links. Compared with foreign powder forged connecting rod, the difference is not very big. The process can meet the requirements of connecting rod blank making.
In order to study the manufacturing process of laser 3-D printing for automobile engine connecting rods, by means of theoretical analysis and experimental verification, 3-D model of a connecting rod was established and slicing was done. By S-type scanning and contour offset scanning, two machining paths of connecting rods were planned. Alloy powders based on iron and the corresponding technological parameters were selected to carry out the rod print test in a laser 3-D printing system. It took 4min30s~4min56s to scanning a single layer and it took 4h20min totally. The results show that the metallographic structure at the bottom of the forming zone of the connecting rod is mainly columnar crystal and dendritic crystal. The middle and upper part are small equiaxed crystal. Interlayer is dense and good metallurgical bonding had been formed. The microhardness of the formed connecting rod is 450HV~490HV, yield strength is 754MPa, tensile strength is 1189MPa, and elongation rate was 9%. Compared to forging, powder forging manufacturing processes, laser 3-D printing forming reduces tooling costs and shortens the production preparation time. Its mechanical properties, such as yield strength and tensile strength, exceed those of steel forging links. Compared with foreign powder forged connecting rod, the difference is not very big. The process can meet the requirements of connecting rod blank making.
2018, 42(1): 141-144.
doi: 10.7510/jgjs.issn.1001-3806.2018.01.028
Abstract:
In order to study propagation properties of Hermite-Gaussian beams in photorefractive saturable nonlinear media, finite difference method was used to solve the evolution equation of light wave numerically and analyze the propagation properties of Hermite-Gaussian beams theoretically. The results show that, under suitable nonlinear conditions, 1-D Hermite-Gaussian beams of 1-order, 2-order and 3-order can form the solitons in respiratory mode during the propagation in photorefractive nonlinear media. With the increase of nonlinearity, the separation tendency among light field components of Hermite-Gaussian beams would become weaker. At the same time, the amplitude fluctuation effect of each light field component would be more obvious. The changes of incident position and incident angle of Hermite-Gaussian beams have no influence on its propagation characteristics. The transmission characteristics of 2-D Hermite-Gaussian beams are similar to those of 1-D. These properties of Hermite-Gaussian beams have certain application prospects in the field of optical switching.
In order to study propagation properties of Hermite-Gaussian beams in photorefractive saturable nonlinear media, finite difference method was used to solve the evolution equation of light wave numerically and analyze the propagation properties of Hermite-Gaussian beams theoretically. The results show that, under suitable nonlinear conditions, 1-D Hermite-Gaussian beams of 1-order, 2-order and 3-order can form the solitons in respiratory mode during the propagation in photorefractive nonlinear media. With the increase of nonlinearity, the separation tendency among light field components of Hermite-Gaussian beams would become weaker. At the same time, the amplitude fluctuation effect of each light field component would be more obvious. The changes of incident position and incident angle of Hermite-Gaussian beams have no influence on its propagation characteristics. The transmission characteristics of 2-D Hermite-Gaussian beams are similar to those of 1-D. These properties of Hermite-Gaussian beams have certain application prospects in the field of optical switching.
