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RSS2017 Vol. 41, No. 2
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2017, 41(2): 151-158.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.001
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Abstract:
In order to measure the phase of mid-infrared field and to obtain the attosecond pulse, the investigation on mid-infrared field phase measurement and attosecond pulse generation has been presented by using the relationship between phase and harmonic cutoff energy. With the introduction of a few-cycle pulse to mid-infrared field, the effect of phase of the combined field on harmonic cutoff energy became much more distinct in comparison with the single field. One new method of phase measurement was gotten. Further, harmonic extension spectra and attosecond pulse generation of the three-color mid-infrared field were numerically investigated. The results show that by properly adjusting the delay times and phases of three pulses, not only harmonic cutoff energy is extended, but also single quantum path is selected to contribute to the harmonic generation, resulting in supercontinuum with bandwidth of 272eV. Finally, by superposing the properly selected harmonics in supercontinuum region, a series of X-ray pulses with pulsewidth of 34as can be obtained. The investigation is helpful for phase measurement of mid-infrared field and attosecond pulse generation.
In order to measure the phase of mid-infrared field and to obtain the attosecond pulse, the investigation on mid-infrared field phase measurement and attosecond pulse generation has been presented by using the relationship between phase and harmonic cutoff energy. With the introduction of a few-cycle pulse to mid-infrared field, the effect of phase of the combined field on harmonic cutoff energy became much more distinct in comparison with the single field. One new method of phase measurement was gotten. Further, harmonic extension spectra and attosecond pulse generation of the three-color mid-infrared field were numerically investigated. The results show that by properly adjusting the delay times and phases of three pulses, not only harmonic cutoff energy is extended, but also single quantum path is selected to contribute to the harmonic generation, resulting in supercontinuum with bandwidth of 272eV. Finally, by superposing the properly selected harmonics in supercontinuum region, a series of X-ray pulses with pulsewidth of 34as can be obtained. The investigation is helpful for phase measurement of mid-infrared field and attosecond pulse generation.
2017, 41(2): 159-162.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.002
Abstract:
In order to research and develop compact radio frequency(RF)-excited waveguide laser and study the factors affecting laser output performance, a compact RF-excited rectangle waveguide CO2 laser was designed and developed by using parallel plane resonator and inner electrode structure. Output mirror of transmissivity 20% was used in the experiment. Under the gas pressure of 14kPa, laser power is up to 12W and the optimal electron-photon conversion efficiency reaches 9.4%. The results show that gas pressure and input power are the main factors affecting laser output performance. The experimental results achieve the expected experimental results and provide technical references for the development of this type of appliance.
In order to research and develop compact radio frequency(RF)-excited waveguide laser and study the factors affecting laser output performance, a compact RF-excited rectangle waveguide CO2 laser was designed and developed by using parallel plane resonator and inner electrode structure. Output mirror of transmissivity 20% was used in the experiment. Under the gas pressure of 14kPa, laser power is up to 12W and the optimal electron-photon conversion efficiency reaches 9.4%. The results show that gas pressure and input power are the main factors affecting laser output performance. The experimental results achieve the expected experimental results and provide technical references for the development of this type of appliance.
2017, 41(2): 163-168.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.003
Abstract:
In order to meet the needs of environmental monitoring, one gas absorption pool was developed. The gas pool could monitor the composition of volatile organic compounds (VOCs) on-line with high sensitivity and high fidelity, and was suitable for the equipment with Fourier transform infrared spectrum detection device. The method of combination of finite element analysis and optical trace was used to do optimization design of gas pool lens clamping adjustment and the fixed mode of optical whole structure. The problem of distortion correction of optical devices in VOCs monitoring of gas pool was solved effectively. The energy transmission efficiency can be optimized in the working range of 80℃ to 180℃. The method of optimization design of absorption pool output energy, suitable for VOCs gas and at specific temperature, was presented. Based on the method, one type of gas absorption pool was designed and the thermal environment test was carried out. The results show that, the absorption pool has stable transmission efficiency in the working range of 80℃~180℃ and can be applied in on-line VOCs sensing system.
In order to meet the needs of environmental monitoring, one gas absorption pool was developed. The gas pool could monitor the composition of volatile organic compounds (VOCs) on-line with high sensitivity and high fidelity, and was suitable for the equipment with Fourier transform infrared spectrum detection device. The method of combination of finite element analysis and optical trace was used to do optimization design of gas pool lens clamping adjustment and the fixed mode of optical whole structure. The problem of distortion correction of optical devices in VOCs monitoring of gas pool was solved effectively. The energy transmission efficiency can be optimized in the working range of 80℃ to 180℃. The method of optimization design of absorption pool output energy, suitable for VOCs gas and at specific temperature, was presented. Based on the method, one type of gas absorption pool was designed and the thermal environment test was carried out. The results show that, the absorption pool has stable transmission efficiency in the working range of 80℃~180℃ and can be applied in on-line VOCs sensing system.
2017, 41(2): 169-173.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.004
Abstract:
In order to meet the need of precise compensation of chromatic dispersion in optical fiber link with long distance and high bit rate, channel dispersion measurement technique based on second order lowest power of radio frequency (RF) signal was studied and demonstrated. The chromatic dispersion in optical fiber link was measured by the phase difference between RF signals that loaded to two sidebands of spectrum. By loading RF signal on the transmitter, the periodic relationship between the power of RF signal in the receiver and optical fiber dispersion was obtained. The position of second lowest RF signal power was gotten by simulation of relationship curve between the power of RF signal in the receiver and optical fiber dispersion. The results show that, the dispersion measuring error in this system is in the range of ±10ps/nm. Comparing with the technique based on first order lowest power of RF signal, dispersion measuring technique based on second order lowest power of RF signal can satisfy the need of measuring large fiber dispersion for high chromatic dispersion value.
In order to meet the need of precise compensation of chromatic dispersion in optical fiber link with long distance and high bit rate, channel dispersion measurement technique based on second order lowest power of radio frequency (RF) signal was studied and demonstrated. The chromatic dispersion in optical fiber link was measured by the phase difference between RF signals that loaded to two sidebands of spectrum. By loading RF signal on the transmitter, the periodic relationship between the power of RF signal in the receiver and optical fiber dispersion was obtained. The position of second lowest RF signal power was gotten by simulation of relationship curve between the power of RF signal in the receiver and optical fiber dispersion. The results show that, the dispersion measuring error in this system is in the range of ±10ps/nm. Comparing with the technique based on first order lowest power of RF signal, dispersion measuring technique based on second order lowest power of RF signal can satisfy the need of measuring large fiber dispersion for high chromatic dispersion value.
2017, 41(2): 174-177.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.005
Abstract:
In order to achieve the optimum parameters of laser-induced backside wet etching for the fabrication of microchannel of silica glass, experiments were made by changing the laser power, etching velocity and magnification times of microscope objective. The processing samples were observed and measured by digital microscope. And then, the topography of microchannels was analyzed. The results show that, under the experimental conditions of laser power of 50mW, etching velocity of 0.010mm/s and 20× microscope objective lens, microchannels of silica glass were fabricated with the depth of 1466μm and the ratio of depth to width of 32. This research has certain application value for micronano fabrication technology of 3-D structure.
In order to achieve the optimum parameters of laser-induced backside wet etching for the fabrication of microchannel of silica glass, experiments were made by changing the laser power, etching velocity and magnification times of microscope objective. The processing samples were observed and measured by digital microscope. And then, the topography of microchannels was analyzed. The results show that, under the experimental conditions of laser power of 50mW, etching velocity of 0.010mm/s and 20× microscope objective lens, microchannels of silica glass were fabricated with the depth of 1466μm and the ratio of depth to width of 32. This research has certain application value for micronano fabrication technology of 3-D structure.
2017, 41(2): 178-181.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.006
Abstract:
To research the effect of Rayleigh surface wave induced by laser shock on the surface crack detection of materials, an equivalent model of laser ultrasonic nondestructive testing was established by using ABAQUS. The process of Rayleigh wave aroused by laser shocking and the propagating process of Rayleigh wave on the surface were simulated. Considering laser parameters, laser shock was equivalent to force impact according to peak pressure, spatial distribution and time distribution. Infinite elements were used to eliminate echo waves. By analyzing the Rayleigh surface wave signal on the receiver point, the effect of surface crack depth on Rayleigh wave echo peak was compared quantitatively. The result shows that, linear relationship exists between the rate of the positive peak value of Rayleigh wave and the time of the next maximum forward displacement and surface crack depth. The results provide a method for experimental measuring on the surface crack.
To research the effect of Rayleigh surface wave induced by laser shock on the surface crack detection of materials, an equivalent model of laser ultrasonic nondestructive testing was established by using ABAQUS. The process of Rayleigh wave aroused by laser shocking and the propagating process of Rayleigh wave on the surface were simulated. Considering laser parameters, laser shock was equivalent to force impact according to peak pressure, spatial distribution and time distribution. Infinite elements were used to eliminate echo waves. By analyzing the Rayleigh surface wave signal on the receiver point, the effect of surface crack depth on Rayleigh wave echo peak was compared quantitatively. The result shows that, linear relationship exists between the rate of the positive peak value of Rayleigh wave and the time of the next maximum forward displacement and surface crack depth. The results provide a method for experimental measuring on the surface crack.
2017, 41(2): 182-186.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.007
Abstract:
In order to meet the requirements for online real-time detection of complex surface quality of parts based on machine vision, based on the double telecentric imaging principle and aberration theory, a double telecentric optical system with wide field of view and large depth of field was designed by using ZEMAX optical design software. The system consisted of six lenses, with working wavelength of the visible range, system magnification of -0.061, working distance greater than 390mm and the maximum field of view of 180mm. The results show that the maximum distortion of optical system is less than 0.1%, the range of depth of field reaches to 80mm, the modulation transfer function in the whole field of 100lp/mm is greater than 0.4 and the maximum of telecentric is controlled within 0.012°. Various aberrations are corrected very well and the image quality is good. The design of structure meets overall design requirements of double telecentric system.
In order to meet the requirements for online real-time detection of complex surface quality of parts based on machine vision, based on the double telecentric imaging principle and aberration theory, a double telecentric optical system with wide field of view and large depth of field was designed by using ZEMAX optical design software. The system consisted of six lenses, with working wavelength of the visible range, system magnification of -0.061, working distance greater than 390mm and the maximum field of view of 180mm. The results show that the maximum distortion of optical system is less than 0.1%, the range of depth of field reaches to 80mm, the modulation transfer function in the whole field of 100lp/mm is greater than 0.4 and the maximum of telecentric is controlled within 0.012°. Various aberrations are corrected very well and the image quality is good. The design of structure meets overall design requirements of double telecentric system.
2017, 41(2): 187-190.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.008
Abstract:
In order to study the focusing properties of radial vector Gaussian beam with vortex phase encoding through objective mirror with high numerical aperture, the vector integral theory and numerical simulation method proposed by RICHARDS and WOLF were adopted. After theoretical analysis and simulation verification of the characteristics of focused field, the relationship between focused field distribution and vortex phase physical parameters was gotten. The results show that, when radial vector Gaussian beam is encoded by single vortex, 2-D radial and longitudinal components of focused field can be obtained. When radial vector Gaussian beam is encoded by double vortex phase symmetrically, two optical dark cores are formed in focal plane. The refractive indexs of two optical dark cores are lower than the indexs of the surrounding environment. The study is helpful to improve the flexibility of optical micro-manipulation and capture and control the double minute.
In order to study the focusing properties of radial vector Gaussian beam with vortex phase encoding through objective mirror with high numerical aperture, the vector integral theory and numerical simulation method proposed by RICHARDS and WOLF were adopted. After theoretical analysis and simulation verification of the characteristics of focused field, the relationship between focused field distribution and vortex phase physical parameters was gotten. The results show that, when radial vector Gaussian beam is encoded by single vortex, 2-D radial and longitudinal components of focused field can be obtained. When radial vector Gaussian beam is encoded by double vortex phase symmetrically, two optical dark cores are formed in focal plane. The refractive indexs of two optical dark cores are lower than the indexs of the surrounding environment. The study is helpful to improve the flexibility of optical micro-manipulation and capture and control the double minute.
2017, 41(2): 191-195.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.009
Abstract:
In order to solve the problem of non-uniform running speed of collagen casing production line, length change before and after retraction, and error caused by the lack of identification marks in cutting position of the cutter, a new collagen casing length detection method, spraying mark detection, was used, and a set of high-precision photoelectric detection system was designed to cut the fixed-length collagen casing. Based on microcontroller unit TM4C123GH6PM and using electro-optic rotary encoder, inkjet printer and digital color-sensing fiber sensor as the main devices, and utilizing the casings stretching facility in factory, the system makes the theoretical and experimental verification during the process of the cutting fixed-length collagen casing. The results show that the measurement accuracy of casing reaches 0.1mm, and the error cutting reduces from ±0.3m to ±0.05m. The average cost of produce for each casing can be reduced by 4%. The photoelectric detection system is suitable for industrial applications and can greatly enhance the competitiveness of enterprises.
In order to solve the problem of non-uniform running speed of collagen casing production line, length change before and after retraction, and error caused by the lack of identification marks in cutting position of the cutter, a new collagen casing length detection method, spraying mark detection, was used, and a set of high-precision photoelectric detection system was designed to cut the fixed-length collagen casing. Based on microcontroller unit TM4C123GH6PM and using electro-optic rotary encoder, inkjet printer and digital color-sensing fiber sensor as the main devices, and utilizing the casings stretching facility in factory, the system makes the theoretical and experimental verification during the process of the cutting fixed-length collagen casing. The results show that the measurement accuracy of casing reaches 0.1mm, and the error cutting reduces from ±0.3m to ±0.05m. The average cost of produce for each casing can be reduced by 4%. The photoelectric detection system is suitable for industrial applications and can greatly enhance the competitiveness of enterprises.
2017, 41(2): 196-199.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.010
Abstract:
In order to study the enhanced optical transmission characteristics of subwavelength compact metal column arrays film on the glass substrates, 3-D finite difference time domain method was adopted to simulate. The enhanced optical transmission spectrum of the film presented a single main peak structure. The peak position and bandwidth of transmission spectrum were different due to the difference of the metal column array period and metal column height. Au and Ag metal model were calculated and analyzed for optimization. The results show that the peak value of the normalized transmittance of Ag column arrays can reach 4.55. By altering array period, the peak wavelength changes between 800nm to 1600nm. The full width at half maximum of transmission band will increase from 220nm to 380nm. The study provides a new solution for the design of micro device about optical band-pass filter.
In order to study the enhanced optical transmission characteristics of subwavelength compact metal column arrays film on the glass substrates, 3-D finite difference time domain method was adopted to simulate. The enhanced optical transmission spectrum of the film presented a single main peak structure. The peak position and bandwidth of transmission spectrum were different due to the difference of the metal column array period and metal column height. Au and Ag metal model were calculated and analyzed for optimization. The results show that the peak value of the normalized transmittance of Ag column arrays can reach 4.55. By altering array period, the peak wavelength changes between 800nm to 1600nm. The full width at half maximum of transmission band will increase from 220nm to 380nm. The study provides a new solution for the design of micro device about optical band-pass filter.
2017, 41(2): 200-204.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.011
Abstract:
In order to solve the problem that the output power and wavelength of semiconductor laser light source was easily influenced by drive current and working temperature in Brillouin optical fiber sensing system, high-precision constant current drive and temperature control circuit were designed. Deep negative feedback integrated circuit was used to control the laser drive current precisely. Integrated temperature control chip MAX1978 was adopted to control the working current of semiconductor coolers and achieve the accurate controlment of laser working temperature. The results show that the design achieves the adjustment of drive current from 0mA~100mA. The maximum relative error of current control is 0.06%, current stability is 0.02% and the maximum error of temperature control is 0.03℃. Under the condition of temperature control, the stability of optical power is 0.5%, and the largest drift is 0.005dBm. The design can achieve the effective control of current and temperature and ensure the stability of output light.
In order to solve the problem that the output power and wavelength of semiconductor laser light source was easily influenced by drive current and working temperature in Brillouin optical fiber sensing system, high-precision constant current drive and temperature control circuit were designed. Deep negative feedback integrated circuit was used to control the laser drive current precisely. Integrated temperature control chip MAX1978 was adopted to control the working current of semiconductor coolers and achieve the accurate controlment of laser working temperature. The results show that the design achieves the adjustment of drive current from 0mA~100mA. The maximum relative error of current control is 0.06%, current stability is 0.02% and the maximum error of temperature control is 0.03℃. Under the condition of temperature control, the stability of optical power is 0.5%, and the largest drift is 0.005dBm. The design can achieve the effective control of current and temperature and ensure the stability of output light.
2017, 41(2): 205-209.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.012
Abstract:
In order to study absorption properties of Tamm state of two kinds of polarized light in silver-photonic crystal-silver structure, by using Drude-Lorentz dispersion model of silver dielectric constant and the characteristic matrix method, the variations of absorption rate with the change of incident angle, cycle number and silver layer thickness were studied. The results show that, two optical Tamm states would appear in two kinds of polarized lights in silver-photonic crystal-silver structure:OTS1 and OTS2. The absorption peak value would increase gradually with the increase of incidence angle, increase slowly with the increase of cycle number, and increase obviously with the increase of silver thickness. The study makes the deep understanding of absorption characteristics of Tamm state of two kinds of polarized light in silver-photonic crystal-silver structure.
In order to study absorption properties of Tamm state of two kinds of polarized light in silver-photonic crystal-silver structure, by using Drude-Lorentz dispersion model of silver dielectric constant and the characteristic matrix method, the variations of absorption rate with the change of incident angle, cycle number and silver layer thickness were studied. The results show that, two optical Tamm states would appear in two kinds of polarized lights in silver-photonic crystal-silver structure:OTS1 and OTS2. The absorption peak value would increase gradually with the increase of incidence angle, increase slowly with the increase of cycle number, and increase obviously with the increase of silver thickness. The study makes the deep understanding of absorption characteristics of Tamm state of two kinds of polarized light in silver-photonic crystal-silver structure.
2017, 41(2): 210-212.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.013
Abstract:
In order to design an effective anti-interference control system in discharge electromagnetic interference environment with excimer laser, the method of all-fiber-interface design and high-precision analog signal transmission based on voltage frequency conversion were taken. After theoretical analysis and experimental verification, the data of space electromagnetic interference intensity of discharge excimer laser and voltage frequency conversion waveform were collected. The results show that, under the condition of the max electric field intensity within 14V/m and the max magnetic field intensity within 38A/m, the system of transmitting the analog signal works stably and reliably with error of less than 2.5%. The study is helpful for analyzing and designing stable and anti-interference excimer laser control system.
In order to design an effective anti-interference control system in discharge electromagnetic interference environment with excimer laser, the method of all-fiber-interface design and high-precision analog signal transmission based on voltage frequency conversion were taken. After theoretical analysis and experimental verification, the data of space electromagnetic interference intensity of discharge excimer laser and voltage frequency conversion waveform were collected. The results show that, under the condition of the max electric field intensity within 14V/m and the max magnetic field intensity within 38A/m, the system of transmitting the analog signal works stably and reliably with error of less than 2.5%. The study is helpful for analyzing and designing stable and anti-interference excimer laser control system.
2017, 41(2): 213-220.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.014
Abstract:
The high-energy laser (HEL) system proposed by General Atomics Aeronautical System, Inc. (GA-ASI) has been developed to the third generation system, which supported by high energy liquid laser area defense system (HELLADS) program and approved by U.S. government recently. Firstly, HELLADS program is reviewed. Some information, such as background, development phases, funds, relative technology developments and so on, is introduced. Secondly, system structure, technical route, pumping mode, technical characteristics and performance indexs of HEL of GA-ASI are studied in detail. Compact lithium ion battery is used as power of the third generation of HEL. The output power is 75kW, beam quality is β < 2, electrical to optical efficiency is nearly 30%, module size is 1.3m×0.4m×0.5m, weight/power ratio is 4kg/kW and continuous running time is more than 30s. The third generation of HEL is suitable for installation on all kinds of small tactical platform. Finally, the technical approach to amplify output power calibration of the laser is reviewed, and the future development direction of the laser is discussed.
The high-energy laser (HEL) system proposed by General Atomics Aeronautical System, Inc. (GA-ASI) has been developed to the third generation system, which supported by high energy liquid laser area defense system (HELLADS) program and approved by U.S. government recently. Firstly, HELLADS program is reviewed. Some information, such as background, development phases, funds, relative technology developments and so on, is introduced. Secondly, system structure, technical route, pumping mode, technical characteristics and performance indexs of HEL of GA-ASI are studied in detail. Compact lithium ion battery is used as power of the third generation of HEL. The output power is 75kW, beam quality is β < 2, electrical to optical efficiency is nearly 30%, module size is 1.3m×0.4m×0.5m, weight/power ratio is 4kg/kW and continuous running time is more than 30s. The third generation of HEL is suitable for installation on all kinds of small tactical platform. Finally, the technical approach to amplify output power calibration of the laser is reviewed, and the future development direction of the laser is discussed.
2017, 41(2): 221-224.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.015
Abstract:
In order to acquire the characteristics of long-range surface plasma wave, such as the resonance angle, full width at half maximum of resonance peak and depth of attenuation peak, a prism coupling method was used to excite the long-range plasma surface wave of media-metal film-media symmetrical structure. The influences of the changes of material film material, metal film thickness, medium refractive index, medium thickness and other parameters on the characteristics of long-range surface plasma wave were studied. The results show that, the full width at half maximum of the attenuation peak of long-range surface plasma wave is narrower about 1 or 2 orders of magnitude than that of traditional surface plasma wave. When the dielectric film thickness is 500nm and 1300nm, the attenuation depth of plasma surface wave is only about 1/2 of those of dielectric film thickness 700nm and 1000nm. The full width at half maximum decreases with the increasing of dielectric film thickness. The thinner metal film is, the deeper attenuation depth is, the smaller full width at half maximum of attenuation peak is. The changes of medium refractive index has no obvious influence on full width at half maximum. The various metal film parameters will change the position of resonance peak. The study provides the effective basis for the application of long-range surface plasma wave in sensing, waveguide, and biosensors field.
In order to acquire the characteristics of long-range surface plasma wave, such as the resonance angle, full width at half maximum of resonance peak and depth of attenuation peak, a prism coupling method was used to excite the long-range plasma surface wave of media-metal film-media symmetrical structure. The influences of the changes of material film material, metal film thickness, medium refractive index, medium thickness and other parameters on the characteristics of long-range surface plasma wave were studied. The results show that, the full width at half maximum of the attenuation peak of long-range surface plasma wave is narrower about 1 or 2 orders of magnitude than that of traditional surface plasma wave. When the dielectric film thickness is 500nm and 1300nm, the attenuation depth of plasma surface wave is only about 1/2 of those of dielectric film thickness 700nm and 1000nm. The full width at half maximum decreases with the increasing of dielectric film thickness. The thinner metal film is, the deeper attenuation depth is, the smaller full width at half maximum of attenuation peak is. The changes of medium refractive index has no obvious influence on full width at half maximum. The various metal film parameters will change the position of resonance peak. The study provides the effective basis for the application of long-range surface plasma wave in sensing, waveguide, and biosensors field.
2017, 41(2): 225-230.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.016
Abstract:
In order to discuss approximation degree of calculating equivalent reflectivity and other parameters of the fiber Bragg grating external cavity laser diode by using two equivalent cavity models of the three cavity mirrors approximation or the coupled cavity approximation and choose the best one, the threshold gain characteristic curves of two approximation models by using apodized fiber Bragg grating and normal fiber Bragg grating were gotten after numerical caculation and simulation. Numerical analysis results show that three cavity mirrors approximate model is more in line with the actual situation when using the apodized fiber Bragg grating. This conclusion has the reference in analysing and designing single longitudinal mode fiber grating external cavity semiconductor laser.
In order to discuss approximation degree of calculating equivalent reflectivity and other parameters of the fiber Bragg grating external cavity laser diode by using two equivalent cavity models of the three cavity mirrors approximation or the coupled cavity approximation and choose the best one, the threshold gain characteristic curves of two approximation models by using apodized fiber Bragg grating and normal fiber Bragg grating were gotten after numerical caculation and simulation. Numerical analysis results show that three cavity mirrors approximate model is more in line with the actual situation when using the apodized fiber Bragg grating. This conclusion has the reference in analysing and designing single longitudinal mode fiber grating external cavity semiconductor laser.
2017, 41(2): 231-234.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.017
Abstract:
To study the effects of laser shock processing (LSP) on the high-cycle fatigue properties of titanium alloy, TC17 titanium alloy was treated by LSP. The TC17 samples with or without the treatment by LSP were evaluated by high frequency fatigue experiment. The fatigue fracture and microstructures were observed by scanning electron microscope and transmission electron microscope. After two times of LSP treatment by 7J laser energy, the fatigue life of the material under 300MPa increased two times of those of the material without treatment. Compared with the base metal samples, crack source of the strengthened specimen was located in the subsurface layer. The fatigue bands in expansion zone arranged more closely. The results show that, after LSP treatment, high density of dislocations and dislocation tangles are produced in the surface hardening region of samples. The defects can effectively prevent the initiation and extension of fatigue crack and improve the high-cycle fatigue performance of TC17 titanium alloy.
To study the effects of laser shock processing (LSP) on the high-cycle fatigue properties of titanium alloy, TC17 titanium alloy was treated by LSP. The TC17 samples with or without the treatment by LSP were evaluated by high frequency fatigue experiment. The fatigue fracture and microstructures were observed by scanning electron microscope and transmission electron microscope. After two times of LSP treatment by 7J laser energy, the fatigue life of the material under 300MPa increased two times of those of the material without treatment. Compared with the base metal samples, crack source of the strengthened specimen was located in the subsurface layer. The fatigue bands in expansion zone arranged more closely. The results show that, after LSP treatment, high density of dislocations and dislocation tangles are produced in the surface hardening region of samples. The defects can effectively prevent the initiation and extension of fatigue crack and improve the high-cycle fatigue performance of TC17 titanium alloy.
2017, 41(2): 235-239.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.018
Abstract:
In order to realize the measurement of micro displacement, a displacement detection system based on semiconductor laser with single mode optical fiber output and 2-D position sensitive detector(PSD) was developed to suppress ambient light noise effectively. The output power of laser was sinusoidally changed when injection current was modulated with 1kHz. The desired signals from PSD which is illuminated by the modulated light source are demodulated from the noise with phase-sensitive detection technique. In the signal processing circuit, using phase sensitive detection technology, the output alternating current signal of detector was demodulated and spot energy center position was gotten. Therefore, the disturbance of background light was eliminated. The results show that the measuring accuracy is better than 1μm. The study is helpful for multi-degree-of-freedom errors measurement.
In order to realize the measurement of micro displacement, a displacement detection system based on semiconductor laser with single mode optical fiber output and 2-D position sensitive detector(PSD) was developed to suppress ambient light noise effectively. The output power of laser was sinusoidally changed when injection current was modulated with 1kHz. The desired signals from PSD which is illuminated by the modulated light source are demodulated from the noise with phase-sensitive detection technique. In the signal processing circuit, using phase sensitive detection technology, the output alternating current signal of detector was demodulated and spot energy center position was gotten. Therefore, the disturbance of background light was eliminated. The results show that the measuring accuracy is better than 1μm. The study is helpful for multi-degree-of-freedom errors measurement.
2017, 41(2): 240-246.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.019
Abstract:
In order to investigate the electronic properties of 4H-SiC crystal under high power laser irradiation, the first principles with pseudo potential method based on density functional perturbation theory was applied to theoretically analyze and experimentally verify the electronic properties of wurtzite 4H-SiC crystal under the strong laser irradiation. The results indicate that 4H-SiC remains semiconductor with indirect band-gap in the range of 0eV~2.75eV. When the electronic temperature reaches above 3.0eV, the crystal turns to be semiconductor with direct band-gap. The forbidden bandwidth increases with the rising of Te in the range of 0eV and 2.0eV, and the forbidden bandwidth quickly reduces with the rising of Te in the range of 2.0eV~3.5eV. When Te is over 3.5eV, the gap has disappeared and metallic properties are presented. The study will be helpful for making special function electronic components of 4H-SiC crystal.
In order to investigate the electronic properties of 4H-SiC crystal under high power laser irradiation, the first principles with pseudo potential method based on density functional perturbation theory was applied to theoretically analyze and experimentally verify the electronic properties of wurtzite 4H-SiC crystal under the strong laser irradiation. The results indicate that 4H-SiC remains semiconductor with indirect band-gap in the range of 0eV~2.75eV. When the electronic temperature reaches above 3.0eV, the crystal turns to be semiconductor with direct band-gap. The forbidden bandwidth increases with the rising of Te in the range of 0eV and 2.0eV, and the forbidden bandwidth quickly reduces with the rising of Te in the range of 2.0eV~3.5eV. When Te is over 3.5eV, the gap has disappeared and metallic properties are presented. The study will be helpful for making special function electronic components of 4H-SiC crystal.
2017, 41(2): 247-250.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.020
Abstract:
In order to solve the crack caused by thermal stress during the process of laser cutting for the toughened glass, the FLUENT software was adopted to analysis the water presure and the stability of water beam based on water & laser coupling model, and the optimised parameters were obtained. Then experiment based on the optimised parameters was conducted to verify the anslysis results. The results show that, incision surfaces of both No.1 and No.2 samples are smooth and slot with the width of 100μm under the condition of nozzle diameter 0.4mm, water pressure 20MPa, laser power 48W and cutting speed 20mm/s. Thedesign of coupling device with two water filling nozzles is applicable in the whole process of laser cutting for the toughened glass.
In order to solve the crack caused by thermal stress during the process of laser cutting for the toughened glass, the FLUENT software was adopted to analysis the water presure and the stability of water beam based on water & laser coupling model, and the optimised parameters were obtained. Then experiment based on the optimised parameters was conducted to verify the anslysis results. The results show that, incision surfaces of both No.1 and No.2 samples are smooth and slot with the width of 100μm under the condition of nozzle diameter 0.4mm, water pressure 20MPa, laser power 48W and cutting speed 20mm/s. Thedesign of coupling device with two water filling nozzles is applicable in the whole process of laser cutting for the toughened glass.
2017, 41(2): 251-254.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.021
Abstract:
In order to improve the capability of wind lidar, based on mathematics modeling method and circulator principle, the transmitted beam quality of circulator was analyzed. The influence of divergence angle on the peak intensity at target distance was discussed. The definition of coupling efficiency of circulator was proposed. And the influence of misalignment between transmitting and receiving axis on detection range was researched. Experimental platform was built to obtain spot parameters in the far field. The simulation results were verified. The results show that, the relative peak intensity at the same distance decreases with the increasing of divergence angle of transmitted beam. The detection range of lidar is mainly affected by misalignment, and misalignment of mrad would make detection range decrease by 89.7%. Therefore, the collimation ratio of optical antenna should be increased reasonably and the structure precision for adjusting misalignment should be better than 0.1mrad level.
In order to improve the capability of wind lidar, based on mathematics modeling method and circulator principle, the transmitted beam quality of circulator was analyzed. The influence of divergence angle on the peak intensity at target distance was discussed. The definition of coupling efficiency of circulator was proposed. And the influence of misalignment between transmitting and receiving axis on detection range was researched. Experimental platform was built to obtain spot parameters in the far field. The simulation results were verified. The results show that, the relative peak intensity at the same distance decreases with the increasing of divergence angle of transmitted beam. The detection range of lidar is mainly affected by misalignment, and misalignment of mrad would make detection range decrease by 89.7%. Therefore, the collimation ratio of optical antenna should be increased reasonably and the structure precision for adjusting misalignment should be better than 0.1mrad level.
2017, 41(2): 255-259.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.022
Abstract:
In order to study the influence of welding parameters and materials on the morphology of molten pool and keyhole, a coaxial monitoring system was built for fiber laser welding. The images of molten pool and keyhole were collected with 532nm and 808nm narrow band filter. Then, the 808nm laser illuminant was used to increase the light intensity of weld zone. The results indicate that, the detailed images of molten pool, keyhole and full penetration hole can be taken with 808nm narrow band filter under 808nm laser auxiliary illuminant. Under the same welding condition, molten pool and keyhole change in the stability, however, full penetration hole changes obviously with time. The change of weld pool is small. The change of small hole is dynamic and the fluctuation range is small. The dynamic characteristic of full penetration hole is obviously different from that of keyhole. The width of weld pool increases with the increase of laser power and decreases with the increase of welding speed. Coaxial monitoring of different material welding verifies the stability of monitoring system. This research provides theoretical instruction for real-time monitoring of laser welding.
In order to study the influence of welding parameters and materials on the morphology of molten pool and keyhole, a coaxial monitoring system was built for fiber laser welding. The images of molten pool and keyhole were collected with 532nm and 808nm narrow band filter. Then, the 808nm laser illuminant was used to increase the light intensity of weld zone. The results indicate that, the detailed images of molten pool, keyhole and full penetration hole can be taken with 808nm narrow band filter under 808nm laser auxiliary illuminant. Under the same welding condition, molten pool and keyhole change in the stability, however, full penetration hole changes obviously with time. The change of weld pool is small. The change of small hole is dynamic and the fluctuation range is small. The dynamic characteristic of full penetration hole is obviously different from that of keyhole. The width of weld pool increases with the increase of laser power and decreases with the increase of welding speed. Coaxial monitoring of different material welding verifies the stability of monitoring system. This research provides theoretical instruction for real-time monitoring of laser welding.
2017, 41(2): 260-264.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.023
Abstract:
In order to improve the ability of accurate early warning of optical fiber security system, Hilbert-Huang transform (HHT) technology was adopted to analyze the principle of optical fiber vibration sensor's signal. Time-frequency spectrums of different signals were obtained. The comparison of time-frequency spectrums of optical fiber vibration signals by HHT and continuous wavelet transform (CWT) was analyzed. The results show that HHT has an important value in time-frequency analysis of optical fiber security system.
In order to improve the ability of accurate early warning of optical fiber security system, Hilbert-Huang transform (HHT) technology was adopted to analyze the principle of optical fiber vibration sensor's signal. Time-frequency spectrums of different signals were obtained. The comparison of time-frequency spectrums of optical fiber vibration signals by HHT and continuous wavelet transform (CWT) was analyzed. The results show that HHT has an important value in time-frequency analysis of optical fiber security system.
2017, 41(2): 265-269.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.024
Abstract:
In order to realize quasi lossless transmission of signal light on optical fiber link, by using high-order Raman amplification method of injecting the first order and the second order Raman pumping into both ends of fiber symmetrically, the numerical model of fiber optical quasi-lossless transmission system was built and the opmization of the system was carried out. The total power consumption and signal power variation with different pump power combinations of the first order and the second order Raman pump were investigated. The influence of signal power and fiber length on system performance index was studied. The results indicate that, system performance will be worse when signal power is higher than 1mW. And system flatness will be worse obviously when fiber length is longer than 60km. Quasi-lossless transmission can be realized along 60km fiber by utilizing this scheme and different pumping power combination schemes can be designed according to the actual demand of energy consumption and signal flatness.
In order to realize quasi lossless transmission of signal light on optical fiber link, by using high-order Raman amplification method of injecting the first order and the second order Raman pumping into both ends of fiber symmetrically, the numerical model of fiber optical quasi-lossless transmission system was built and the opmization of the system was carried out. The total power consumption and signal power variation with different pump power combinations of the first order and the second order Raman pump were investigated. The influence of signal power and fiber length on system performance index was studied. The results indicate that, system performance will be worse when signal power is higher than 1mW. And system flatness will be worse obviously when fiber length is longer than 60km. Quasi-lossless transmission can be realized along 60km fiber by utilizing this scheme and different pumping power combination schemes can be designed according to the actual demand of energy consumption and signal flatness.
2017, 41(2): 270-274.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.025
Abstract:
In order to study the influence of magnetic field on laser welding, the longitudinal or transverse magnetic field was employed via adding a permanent magnet next to the specimen. Experiment investigation on laser hot wire welding of stainless steel was performed with additional magnetic field. By combining the weld cross section shape and weld microstructure, laser hot wire welding joints under different magnetic fields were analyzed. The results show that, the addition of magnetic field has a significant effect on the welding process and joint shape. The appropriate magnetic induction intensity can stabilize the laser hot wire welding process. But too large magnetic induction intensity would cause a large number of splashes. The shape of welding joint changes with the change of the direction of magnetic field, the polarity of magnetic field, and magnetic induction intensity. Transverse magnetic field can improve the welding efficiency of laser wire. Magnetic field can also decrease the columnar dendrite area, promote the formation of cell crystal, and increase the micro hardness value of weld. The additional magnetic field causes the generation of ampere force in the welding pool. Ampere force is the main force to stir pool. It changes the flow of molten metal and causes the changes of head shape and microstructure of laser hot wire welding.
In order to study the influence of magnetic field on laser welding, the longitudinal or transverse magnetic field was employed via adding a permanent magnet next to the specimen. Experiment investigation on laser hot wire welding of stainless steel was performed with additional magnetic field. By combining the weld cross section shape and weld microstructure, laser hot wire welding joints under different magnetic fields were analyzed. The results show that, the addition of magnetic field has a significant effect on the welding process and joint shape. The appropriate magnetic induction intensity can stabilize the laser hot wire welding process. But too large magnetic induction intensity would cause a large number of splashes. The shape of welding joint changes with the change of the direction of magnetic field, the polarity of magnetic field, and magnetic induction intensity. Transverse magnetic field can improve the welding efficiency of laser wire. Magnetic field can also decrease the columnar dendrite area, promote the formation of cell crystal, and increase the micro hardness value of weld. The additional magnetic field causes the generation of ampere force in the welding pool. Ampere force is the main force to stir pool. It changes the flow of molten metal and causes the changes of head shape and microstructure of laser hot wire welding.
2017, 41(2): 275-279.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.026
Abstract:
In order to implement rapid quantitative phase measurement and imaging for transparent biological tissues, phase grating and other phase objects, based on the principle of in-line interferometry and phase contrast interferometry, an experimental system for fast quantitative measurement and imaging of phase objects was established. The principle of quantitative imaging was analyzed and the corresponding phase extraction and recovery procedures were designed. By shooting one or two phase contrast interferograms, the quantitative phase imagings for phase grating, water microdroplet and other phase objects with small phase variation were realized by the proposed method. A corresponding partition differential phase unwrapping algorithm was designed and the quantitative phase measurement and imaging of micro lens with phase value over π was achieved. The results show that the relationship between phase distribution of the obtained holographic phase grating measured by the system and phase amplitude variation of weak ultrasonic standing wave grating under different ultrasonic driving voltages is basically consistent with the results obtained from other methods. The experimental measurement of micro lens is compared with the theoretical value, and the absolute error is about 0.03μm. This system has certain feasibility, adaptability and potential applications on fast measurement and imaging of transparent phase objects such as biological cells and tissues.
In order to implement rapid quantitative phase measurement and imaging for transparent biological tissues, phase grating and other phase objects, based on the principle of in-line interferometry and phase contrast interferometry, an experimental system for fast quantitative measurement and imaging of phase objects was established. The principle of quantitative imaging was analyzed and the corresponding phase extraction and recovery procedures were designed. By shooting one or two phase contrast interferograms, the quantitative phase imagings for phase grating, water microdroplet and other phase objects with small phase variation were realized by the proposed method. A corresponding partition differential phase unwrapping algorithm was designed and the quantitative phase measurement and imaging of micro lens with phase value over π was achieved. The results show that the relationship between phase distribution of the obtained holographic phase grating measured by the system and phase amplitude variation of weak ultrasonic standing wave grating under different ultrasonic driving voltages is basically consistent with the results obtained from other methods. The experimental measurement of micro lens is compared with the theoretical value, and the absolute error is about 0.03μm. This system has certain feasibility, adaptability and potential applications on fast measurement and imaging of transparent phase objects such as biological cells and tissues.
2017, 41(2): 280-283.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.027
Abstract:
In order to develop ytterbium-doped core material of high-power fiber lasers, lithium silicate glass samples with ingredients 0.70SiO2-0.18Li2CO3-0.04MgCO3-0.04BaCO3-0.02Al2O3-0.02Yb2O3 (mole fraction) were prepared by the method of high temperature melting. Absorption spectrum in the range of 850nm~1100nm and fluorescence spectrum under excitation wavelength of 858nm were measured. Spectral and laser property parameters were theoretically calculated by using experimental data. The results demonstrate that the main fluorescence line with 1036nm wavelength has effective width of 94.1nm, absorption cross section of 1.143pm2, emission cross section of 1.024pm2 and fluorescence lifetime of 0.98ms. The least population of the exciting state is only 0.042 and the most minimal pump intensity is 0.76kW·cm-2. Compared with the recently reported Yb3+-doped laser glasses, the glass samples with these parameters are advantageous. This kind of Yb3+-doped lithium silicate glass is hopeful to apply in the preparation of Yb-doped fiber cores.
In order to develop ytterbium-doped core material of high-power fiber lasers, lithium silicate glass samples with ingredients 0.70SiO2-0.18Li2CO3-0.04MgCO3-0.04BaCO3-0.02Al2O3-0.02Yb2O3 (mole fraction) were prepared by the method of high temperature melting. Absorption spectrum in the range of 850nm~1100nm and fluorescence spectrum under excitation wavelength of 858nm were measured. Spectral and laser property parameters were theoretically calculated by using experimental data. The results demonstrate that the main fluorescence line with 1036nm wavelength has effective width of 94.1nm, absorption cross section of 1.143pm2, emission cross section of 1.024pm2 and fluorescence lifetime of 0.98ms. The least population of the exciting state is only 0.042 and the most minimal pump intensity is 0.76kW·cm-2. Compared with the recently reported Yb3+-doped laser glasses, the glass samples with these parameters are advantageous. This kind of Yb3+-doped lithium silicate glass is hopeful to apply in the preparation of Yb-doped fiber cores.
2017, 41(2): 284-288.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.028
Abstract:
In order to real-time detect the main component of volatile organic compounds of oil gas and realize production safety in petrochemical industry, laser spectrum analysis technique was applied. Firstly, the broadband optical source was utilized to analyze the spectral absorption features of propane between 1686.00nm and 1687.00nm. The relationship between absorption coefficient and wavelength was fit into Lorentz lineshape, with half width at half max of 0.21nm. A distributed feedback laser with center wavelength of 1686.30nm was chosen as the sigle mode light source, and laser wavelength scan was made within wide absorption spectrum of propane. The changing regularity of the first and second harmonic signal with volume fraction of propane was acquired. The linear relationship between the ratio of the second harmonic signal to the first harmonic signal and propane volume fraction was calibrated with propane volume fraction from 0.0050 to 0.0300. The results show that, the system has good stability and repeatability, and can be used to do propane online detection. The study can provide the reference of theory and experiment for detecting other volatile organic compound gases.
In order to real-time detect the main component of volatile organic compounds of oil gas and realize production safety in petrochemical industry, laser spectrum analysis technique was applied. Firstly, the broadband optical source was utilized to analyze the spectral absorption features of propane between 1686.00nm and 1687.00nm. The relationship between absorption coefficient and wavelength was fit into Lorentz lineshape, with half width at half max of 0.21nm. A distributed feedback laser with center wavelength of 1686.30nm was chosen as the sigle mode light source, and laser wavelength scan was made within wide absorption spectrum of propane. The changing regularity of the first and second harmonic signal with volume fraction of propane was acquired. The linear relationship between the ratio of the second harmonic signal to the first harmonic signal and propane volume fraction was calibrated with propane volume fraction from 0.0050 to 0.0300. The results show that, the system has good stability and repeatability, and can be used to do propane online detection. The study can provide the reference of theory and experiment for detecting other volatile organic compound gases.
2017, 41(2): 289-295.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.029
Abstract:
In order to remove the noise of image based on total variation, the denoising problem was converted to optimization problem. Semi-smooth Newton method incorporated by generalized minimum residual method was used to solve the associated optimization problem and non-symmetric linear equations. After theoretical analysis and experimental verification, a great deal of feasible data of removal noise experiment for 1-D signal and 2-D image were obtained by different methods. The results show that semi-smooth Newton method incorporated by generalized minimum residual method converges faster than that incorporated by preconditioned conjugate gradients method and alternating direction method of multipliers algorithm. The proposed method can remove the noise of image effectively.
In order to remove the noise of image based on total variation, the denoising problem was converted to optimization problem. Semi-smooth Newton method incorporated by generalized minimum residual method was used to solve the associated optimization problem and non-symmetric linear equations. After theoretical analysis and experimental verification, a great deal of feasible data of removal noise experiment for 1-D signal and 2-D image were obtained by different methods. The results show that semi-smooth Newton method incorporated by generalized minimum residual method converges faster than that incorporated by preconditioned conjugate gradients method and alternating direction method of multipliers algorithm. The proposed method can remove the noise of image effectively.
2017, 41(2): 296-301.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.030
Abstract:
In order to achieve imaging, detection and alarm of hemisphere space target by photoelectric imaging system, based on large field imaging and aberration theory, fisheye lens of optical system was theoretically analyzed and simulated by the scaling laws. The barrel distortion and stop coma were used to increase the illumination uniformity of image plane. The system axis aberration decreased by means of ray aiming iteration. Imaging quality of the system was evaluated and analyzed multiply. Distortion correction model of imaging lens was derived. The results show that, in visible spectrum, fisheye lens of excellent imaging quality is gotten, with the CCD effective size of 8.446mm×7.042mm, effective pixels of 2448×2050, entire field of view of 180°, focal length of 2.24mm, relative aperture of 1:2.8, image plane illumination uniformity of over 90%, and mean square root radius value of diffuse spot diagram of less than 1/2 pixel. The modulation transfer function with spatial frequency of 145lp/mm is greater than 0.4. The omnidirectional gaze photoelectric imaging system can realize the real-time detection of hemisphere space target.
In order to achieve imaging, detection and alarm of hemisphere space target by photoelectric imaging system, based on large field imaging and aberration theory, fisheye lens of optical system was theoretically analyzed and simulated by the scaling laws. The barrel distortion and stop coma were used to increase the illumination uniformity of image plane. The system axis aberration decreased by means of ray aiming iteration. Imaging quality of the system was evaluated and analyzed multiply. Distortion correction model of imaging lens was derived. The results show that, in visible spectrum, fisheye lens of excellent imaging quality is gotten, with the CCD effective size of 8.446mm×7.042mm, effective pixels of 2448×2050, entire field of view of 180°, focal length of 2.24mm, relative aperture of 1:2.8, image plane illumination uniformity of over 90%, and mean square root radius value of diffuse spot diagram of less than 1/2 pixel. The modulation transfer function with spatial frequency of 145lp/mm is greater than 0.4. The omnidirectional gaze photoelectric imaging system can realize the real-time detection of hemisphere space target.
2017, 41(2): 302-306.
doi: 10.7510/jgjs.issn.1001-3806.2017.02.031
Abstract:
In order to study the proton acceleration of the moving electric field driven by laser radiation pressure, the interaction process between high power laser and laser plasma was analyzed theoretically. 2-D particle-in-cell simulations was used to verify the theoretical analysis result. The results show that when the interaction between ultra-short ultra-intense laser pulse and thin solid flat target in front of the background plasma, a bilayer structure consisted by electron layer and ion layer was generated at the back of the solid target. Under the constant advancement of laser radiation pressure, the double layer structure in the background plasma spreaded at a certain speed and formed a moving electric field. Protons in background plasma were captured by this moving electric field and accelerated to a very high energy. The maximum proton energy reached 20GeV. The results of theoretical analysis are in good agreement with the simulation results of 2-D particle.
In order to study the proton acceleration of the moving electric field driven by laser radiation pressure, the interaction process between high power laser and laser plasma was analyzed theoretically. 2-D particle-in-cell simulations was used to verify the theoretical analysis result. The results show that when the interaction between ultra-short ultra-intense laser pulse and thin solid flat target in front of the background plasma, a bilayer structure consisted by electron layer and ion layer was generated at the back of the solid target. Under the constant advancement of laser radiation pressure, the double layer structure in the background plasma spreaded at a certain speed and formed a moving electric field. Protons in background plasma were captured by this moving electric field and accelerated to a very high energy. The maximum proton energy reached 20GeV. The results of theoretical analysis are in good agreement with the simulation results of 2-D particle.
