Map
WeChat
Email alert
RSS2019 Vol. 43, No. 1
Display Method:
[Abstract]
[PDF 283KB]
2019, 43(1): 1-5.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.001
[FullText HTML]
Abstract:
In order to solve the problem that the laser output energy decreases when laser diode pump wavelength drifts with temperature, the technology of laser diode pump source wavelength matching and concave-convex stable resonator are used to realize temperature-free control. After theoretical analysis and experimental verification, the results show that, when the length of laser cavity is 210mm, electro-optic conversion efficiency is 5.7%. Output single pulse energy is more than 60mJ, and the energy stability is better than 5% in the range of 10℃~30℃. Laser output spot diameter is 4mm, pulse width is 8s, and laser far-field beam divergence angle is 1.1mrad at 10Hz. The experimental results are in agreement with the theoretical analysis. The laser diode side-pumped temperature-free laser can maintain a stable energy output in a certain temperature range. The theoretical analysis and the scheme are of great significance for the study on temperature-free-controlled lasers.
In order to solve the problem that the laser output energy decreases when laser diode pump wavelength drifts with temperature, the technology of laser diode pump source wavelength matching and concave-convex stable resonator are used to realize temperature-free control. After theoretical analysis and experimental verification, the results show that, when the length of laser cavity is 210mm, electro-optic conversion efficiency is 5.7%. Output single pulse energy is more than 60mJ, and the energy stability is better than 5% in the range of 10℃~30℃. Laser output spot diameter is 4mm, pulse width is 8s, and laser far-field beam divergence angle is 1.1mrad at 10Hz. The experimental results are in agreement with the theoretical analysis. The laser diode side-pumped temperature-free laser can maintain a stable energy output in a certain temperature range. The theoretical analysis and the scheme are of great significance for the study on temperature-free-controlled lasers.
2019, 43(1): 6-10.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.002
Abstract:
In order to realize the rapid quantitative detection of heavy metal cadmium (Cd) in table salt, 8 groups of salt samples were made by adding heavy metal element Cd and the self-made 193nm excimer laser was used as excitation source. By choosing Cd Ⅰ 228.8nm characteristic spectrum line as analysis line, laser induced breakdown spectroscopy (LIBS) technology was used in theoretical analysis and experimental verification. The experiment results show that, when the delay time is 1.5μs, the better spectral intensity and signal-to-background ratio can be obtained. The spectral line strength has a good linear relationship with mass fraction of Cd. The fitting degree is 0.984, the predicted relative error is less than 7%, and the detection limit is 0.65mg/kg. LIBS detection technology not only has the fast and convenient advantages without the need of tedious sample preparation, but also has high detection precision. It is a very novel and potential detection technology in the field of rapid detection of food safety.
In order to realize the rapid quantitative detection of heavy metal cadmium (Cd) in table salt, 8 groups of salt samples were made by adding heavy metal element Cd and the self-made 193nm excimer laser was used as excitation source. By choosing Cd Ⅰ 228.8nm characteristic spectrum line as analysis line, laser induced breakdown spectroscopy (LIBS) technology was used in theoretical analysis and experimental verification. The experiment results show that, when the delay time is 1.5μs, the better spectral intensity and signal-to-background ratio can be obtained. The spectral line strength has a good linear relationship with mass fraction of Cd. The fitting degree is 0.984, the predicted relative error is less than 7%, and the detection limit is 0.65mg/kg. LIBS detection technology not only has the fast and convenient advantages without the need of tedious sample preparation, but also has high detection precision. It is a very novel and potential detection technology in the field of rapid detection of food safety.
2019, 43(1): 11-14.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.003
Abstract:
In order to design a wavelength-tunable passively mode-locked thulium-doped fiber laser, the method of changing its working wavelength by adjusting the laser polarization state based on random birefringence effect of laser cavity was proposed. The principle analysis and experimental verification were carried out. The results show that, the adjustable polarization controller can achieve mode-locked pulse output at multiple central wavelengths such as 2010nm, 2019nm, 2024nm, 2050nm, and can also be tuned precisely near a single central wavelength. This kind of tunable mode-locked laser has simple structure and good tunability. It has certain reference value for light source selection in optical communication, ultrafast optics, medicine, remote sensing technology and radar.
In order to design a wavelength-tunable passively mode-locked thulium-doped fiber laser, the method of changing its working wavelength by adjusting the laser polarization state based on random birefringence effect of laser cavity was proposed. The principle analysis and experimental verification were carried out. The results show that, the adjustable polarization controller can achieve mode-locked pulse output at multiple central wavelengths such as 2010nm, 2019nm, 2024nm, 2050nm, and can also be tuned precisely near a single central wavelength. This kind of tunable mode-locked laser has simple structure and good tunability. It has certain reference value for light source selection in optical communication, ultrafast optics, medicine, remote sensing technology and radar.
2019, 43(1): 15-18.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.004
Abstract:
In order to solve the problems of small measurement range of field of view, high precision and difficult measurement in a portable laser communication, link energy at a specified communication distance was used as the basis for measuring the field of view. A measurement method of field of view based on portable laser communication was proposed. A high-precision measurement device was designed and the actual test and measurement were carried out. The results show that, when detector sensitivity is -30dBm, the receiving field of view of laser communication at 1km, 2km, 3km, 4km is 1.12mrad, 0.94mrad, 0.87mrad and 0.63mrad respectively. The test method and device can accurately measure the field of view of a portable laser communication. The test device can be extended to high-precision measurement of small field of view in different fields.
In order to solve the problems of small measurement range of field of view, high precision and difficult measurement in a portable laser communication, link energy at a specified communication distance was used as the basis for measuring the field of view. A measurement method of field of view based on portable laser communication was proposed. A high-precision measurement device was designed and the actual test and measurement were carried out. The results show that, when detector sensitivity is -30dBm, the receiving field of view of laser communication at 1km, 2km, 3km, 4km is 1.12mrad, 0.94mrad, 0.87mrad and 0.63mrad respectively. The test method and device can accurately measure the field of view of a portable laser communication. The test device can be extended to high-precision measurement of small field of view in different fields.
2019, 43(1): 19-24.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.005
Abstract:
In order to study the influence of magnetic field on laser welding, a self-made suspended permanent magnet electromagnetic stirring device was placed above the weldment to provide a transverse rotating magnetic field, and a CO2 laser welding test was performed on the pure nickel Ni201 thin plate. After welding, metallographic microscope and scanning electron microscope were used for observation and analysis, and electrochemical workstation was used to conduct electrochemical corrosion test of welded joints. The test results show that, the weldments can be completely welded with different magnetic field intensity, and the welds are formed well, and the inside of the weld is composed of coarse austenite grain.The magnetic field intensity has little effect on the macroscopic appearance of laser welded joints.With the increase of magnetic field intensity, the solidification microstructure of pure Ni201 laser welded joint is gradually refined, and the corrosion resistance of weld metal is gradually improved. The external rotating magnetic field can promote the heat transfer and mass transfer in the molten pool by electromagnetic stirring, increase the supercooling, increase the nucleation rate, make the grain refined, and improve the corrosion resistance of the weld.
In order to study the influence of magnetic field on laser welding, a self-made suspended permanent magnet electromagnetic stirring device was placed above the weldment to provide a transverse rotating magnetic field, and a CO2 laser welding test was performed on the pure nickel Ni201 thin plate. After welding, metallographic microscope and scanning electron microscope were used for observation and analysis, and electrochemical workstation was used to conduct electrochemical corrosion test of welded joints. The test results show that, the weldments can be completely welded with different magnetic field intensity, and the welds are formed well, and the inside of the weld is composed of coarse austenite grain.The magnetic field intensity has little effect on the macroscopic appearance of laser welded joints.With the increase of magnetic field intensity, the solidification microstructure of pure Ni201 laser welded joint is gradually refined, and the corrosion resistance of weld metal is gradually improved. The external rotating magnetic field can promote the heat transfer and mass transfer in the molten pool by electromagnetic stirring, increase the supercooling, increase the nucleation rate, make the grain refined, and improve the corrosion resistance of the weld.
2019, 43(1): 25-29.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.006
Abstract:
In order to prove that near-infrared diffuse transmission spectroscopy combining with chemometrics can effectively detect the maturity of tomatoes, diffuse transmission spectroscopy data of tomatoes were obtained by using QE65000 spectrometer of Ocean Optics Company of America, and the color datum of brightness, red and green, yellow blue color and total chromatic aberration were obtained by using CR-10 reflectance colorimeter of Konica Minolta of Japan. The color model was established by the standard mathematical modeling method, and the near infrared spectroscopy model was established by the partial least squares regression correction algorithm. The results show that, the red-green phase index was the best for both models. Among the 99 unknown samples, the misjudgments of the color model were immature 0%, semi-mature 33.33% and mature 0%, while the misjudgments of the near-infrared spectroscopy prediction model were immature 32.14%, semi-mature 50% and mature 0% respectively. This study verifies the feasibility of non-destructive detection of tomato maturity by near infrared spectroscopy, which has a certain practical significance for rapid and batch sorting of tomatoes.
In order to prove that near-infrared diffuse transmission spectroscopy combining with chemometrics can effectively detect the maturity of tomatoes, diffuse transmission spectroscopy data of tomatoes were obtained by using QE65000 spectrometer of Ocean Optics Company of America, and the color datum of brightness, red and green, yellow blue color and total chromatic aberration were obtained by using CR-10 reflectance colorimeter of Konica Minolta of Japan. The color model was established by the standard mathematical modeling method, and the near infrared spectroscopy model was established by the partial least squares regression correction algorithm. The results show that, the red-green phase index was the best for both models. Among the 99 unknown samples, the misjudgments of the color model were immature 0%, semi-mature 33.33% and mature 0%, while the misjudgments of the near-infrared spectroscopy prediction model were immature 32.14%, semi-mature 50% and mature 0% respectively. This study verifies the feasibility of non-destructive detection of tomato maturity by near infrared spectroscopy, which has a certain practical significance for rapid and batch sorting of tomatoes.
2019, 43(1): 30-37.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.007
Abstract:
Integrated circuit(IC) lithography, as a typical representative of traditional lithography technology, supports the rapid development of integrated circuit chips. The new generation of photolithography technology has the advantages of diverse technology, high precision and high efficiency. It has great potential in the development of optoelectronic devices, the realization of 3-D micro-nano structure, and the construction of the ordered nanoscale channels. A variety of new photolithography technologies in recent years have been reviewed. Their characteristics and their applications in nanoelectronics, photonic devices, energy, sensing and other fields have been analyzed. Finally, the development direction of lithography technology in the future is prospected.
Integrated circuit(IC) lithography, as a typical representative of traditional lithography technology, supports the rapid development of integrated circuit chips. The new generation of photolithography technology has the advantages of diverse technology, high precision and high efficiency. It has great potential in the development of optoelectronic devices, the realization of 3-D micro-nano structure, and the construction of the ordered nanoscale channels. A variety of new photolithography technologies in recent years have been reviewed. Their characteristics and their applications in nanoelectronics, photonic devices, energy, sensing and other fields have been analyzed. Finally, the development direction of lithography technology in the future is prospected.
2019, 43(1): 38-42.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.008
Abstract:
In order to research the pores formation mechanism of sealing layer in laser welding of vacuum plate glazing, a laser sealing test was carried out. Scanning electron microscope, energy dispersive spectroscopy, X-ray diffractometer and metallographic microscope were used in this study. The influences of laser power and welding speed on pores of sealing layer were studied and the causes of pores were analyzed. The results show that, there are a large number of isolated pores in vacuum glazing sealing layer, which are different in size and disconnected with each other, located at the junction of particles, and mainly caused by the residual air between the solder particles. At the welding speed of 2mm/s and the defocus amount of -2mm, lower or higher laser power is not conducive to reduce the pore defects of sealing layer. When the laser power is 80W (energy density is 80J/mm2), the sealing layer has good morphology and good sealing quality. The lower welding speed will help to reduce the pore defects of sealing layer at the laser power of 80W and the defocus amount of -2mm. When the welding speed is 1mm/s (energy density is 160J/mm2), the sealing layer has good morphology and good sealing quality. This study can provide a theoretical basis for the laser sealing manufacturing of vacuum plate glazing.
In order to research the pores formation mechanism of sealing layer in laser welding of vacuum plate glazing, a laser sealing test was carried out. Scanning electron microscope, energy dispersive spectroscopy, X-ray diffractometer and metallographic microscope were used in this study. The influences of laser power and welding speed on pores of sealing layer were studied and the causes of pores were analyzed. The results show that, there are a large number of isolated pores in vacuum glazing sealing layer, which are different in size and disconnected with each other, located at the junction of particles, and mainly caused by the residual air between the solder particles. At the welding speed of 2mm/s and the defocus amount of -2mm, lower or higher laser power is not conducive to reduce the pore defects of sealing layer. When the laser power is 80W (energy density is 80J/mm2), the sealing layer has good morphology and good sealing quality. The lower welding speed will help to reduce the pore defects of sealing layer at the laser power of 80W and the defocus amount of -2mm. When the welding speed is 1mm/s (energy density is 160J/mm2), the sealing layer has good morphology and good sealing quality. This study can provide a theoretical basis for the laser sealing manufacturing of vacuum plate glazing.
2019, 43(1): 43-47.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.009
Abstract:
In order to design a new acceleration sensor, resonant optical tunneling effect(ROTE) structure was applied to design the optical sensor. The key factors, such as frequency response and sensitivity performance of the sensor, were simulated and analyzed by using COMSOL software. The experimental platform was built to verify the principle of resonant optical tunneling effect. The results show that the sensitivity of ROTE acceleration sensor is 6.7dB/g when acceleration is 500m/s2 in the range of 100 Hz to 3000Hz. The sensor is deft, simple and has high sensitivity. The study provides a new idea and method for optical sensor and has broad application prospects.
In order to design a new acceleration sensor, resonant optical tunneling effect(ROTE) structure was applied to design the optical sensor. The key factors, such as frequency response and sensitivity performance of the sensor, were simulated and analyzed by using COMSOL software. The experimental platform was built to verify the principle of resonant optical tunneling effect. The results show that the sensitivity of ROTE acceleration sensor is 6.7dB/g when acceleration is 500m/s2 in the range of 100 Hz to 3000Hz. The sensor is deft, simple and has high sensitivity. The study provides a new idea and method for optical sensor and has broad application prospects.
2019, 43(1): 48-52.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.010
Abstract:
In order to obtain optical characteristics of the photonic crystal fiber with double air holes and quadrilateral lattice arrangement, the finite element method was used to simulate the fiber. The results of birefringence, limiting loss, polarization beat length and dispersion characteristics of the fiber were obtained. The results show that, compared with the elliptical air hole photonic crystal fiber with square lattice arrangement, the double air hole photonic crystal fiber with square lattice arrangement can obtain higher birefringence characteristics, reaching 10-2 orders of magnitude, under the same air duty cycle conditions. The limiting loss difference of the two polarization modes of the fiber can reach 103 order of magnitude. This type of optical fiber is easy to manufacture, and has a certain application prospect in optical fiber communication and optical fiber sensing.
In order to obtain optical characteristics of the photonic crystal fiber with double air holes and quadrilateral lattice arrangement, the finite element method was used to simulate the fiber. The results of birefringence, limiting loss, polarization beat length and dispersion characteristics of the fiber were obtained. The results show that, compared with the elliptical air hole photonic crystal fiber with square lattice arrangement, the double air hole photonic crystal fiber with square lattice arrangement can obtain higher birefringence characteristics, reaching 10-2 orders of magnitude, under the same air duty cycle conditions. The limiting loss difference of the two polarization modes of the fiber can reach 103 order of magnitude. This type of optical fiber is easy to manufacture, and has a certain application prospect in optical fiber communication and optical fiber sensing.
2019, 43(1): 53-57.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.011
Abstract:
In order to enhance intensity of high-order harmonic spectrum and attosecond pulse, characteristics of high-order harmonic radiation of H2+ driven by pump probe laser were studied by numerical solution of Schrodinger equation. The results show that H2+ is excited into the multi-photon resonance ionization region at first and then increases the ionization probability under the pump laser. The harmonic radiation intensity is enhanced under the detection laser. The cut-off frequency of the harmonic wave can be further extended when the asymmetric non-uniform laser field is used. The energy peak contribution of single harmonic radiation is obtained. Finally, the pulse width of 32as can be obtained by superposing the harmonics of Fourier transform. This study is helpful for the generation of single attosecond pulses.
In order to enhance intensity of high-order harmonic spectrum and attosecond pulse, characteristics of high-order harmonic radiation of H2+ driven by pump probe laser were studied by numerical solution of Schrodinger equation. The results show that H2+ is excited into the multi-photon resonance ionization region at first and then increases the ionization probability under the pump laser. The harmonic radiation intensity is enhanced under the detection laser. The cut-off frequency of the harmonic wave can be further extended when the asymmetric non-uniform laser field is used. The energy peak contribution of single harmonic radiation is obtained. Finally, the pulse width of 32as can be obtained by superposing the harmonics of Fourier transform. This study is helpful for the generation of single attosecond pulses.
2019, 43(1): 58-62.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.012
Abstract:
In order to improve the light extraction efficiency of light-emitting diodes (LED), the influences of different grating shapes on the light extraction efficiency of LED were compared.The flip chip LEDs, which was integrated with rectangle, isosceles triangle and isosceles trapezoidal grating, were optimized by rigorous coupled wave method to make the transmittance of the light-exiting surface best. Finite-difference time-domain method was used to simulate the efficiency of light extraction. After simulation calculation and theoretical analysis, the optimal grating parameters (grating duty ratio f, grating period p, grating thickness h) and transition layer thickness d of the LEDs with 3 different structures can be obtained: f=0.35, p=150nm, h=80nm, d=190nm; f=0.45, p=175nm, h=80nm, d=190nm; f=0.7, p=150nm, h=80nm, d=190nm. The results show that, in the wavelength of 0.4μm to 0.5μm, the flip-chip LED of the rectangular grating and the flip-chip LED of the isosceles triangle grating have the same transmittance.The flip-chip LED of The isosceles trapezoidal grating has the lowest transmittance. Because of the lowest transmittance, the light extraction efficiency of the flip-chip LED of the isosceles trapezoidal grating is lower and the highest is only 58.07%. The optical extraction efficiency of the flip-chip LED of the isosceles triangle grating with special grating shape can reach 77.75%.The study can provide theoretical guidance for manufacturing high light extraction efficiency LED in the future.
In order to improve the light extraction efficiency of light-emitting diodes (LED), the influences of different grating shapes on the light extraction efficiency of LED were compared.The flip chip LEDs, which was integrated with rectangle, isosceles triangle and isosceles trapezoidal grating, were optimized by rigorous coupled wave method to make the transmittance of the light-exiting surface best. Finite-difference time-domain method was used to simulate the efficiency of light extraction. After simulation calculation and theoretical analysis, the optimal grating parameters (grating duty ratio f, grating period p, grating thickness h) and transition layer thickness d of the LEDs with 3 different structures can be obtained: f=0.35, p=150nm, h=80nm, d=190nm; f=0.45, p=175nm, h=80nm, d=190nm; f=0.7, p=150nm, h=80nm, d=190nm. The results show that, in the wavelength of 0.4μm to 0.5μm, the flip-chip LED of the rectangular grating and the flip-chip LED of the isosceles triangle grating have the same transmittance.The flip-chip LED of The isosceles trapezoidal grating has the lowest transmittance. Because of the lowest transmittance, the light extraction efficiency of the flip-chip LED of the isosceles trapezoidal grating is lower and the highest is only 58.07%. The optical extraction efficiency of the flip-chip LED of the isosceles triangle grating with special grating shape can reach 77.75%.The study can provide theoretical guidance for manufacturing high light extraction efficiency LED in the future.
2019, 43(1): 69-74.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.014
Abstract:
With the development and application of phase sensitive optical time-domain reflectometer (ϕ-OTDR) technology, traditional amplitude demodulation method can not meet the needs of high quality sensing. Phase demodulation method has the advantages of high sensitivity and high accuracy in demodulation of phase information. In recent years, it has attracted wide attention at home and abroad. The research progress of phase demodulation in ϕ-OTDR system is reviewed. Demodulation methods based on phase generated carrier (PGC), 3×3 coupler and digital coherent input-quadrature are introduced respectively. The advantages and disadvantages of these methods are simply analyzed.
With the development and application of phase sensitive optical time-domain reflectometer (ϕ-OTDR) technology, traditional amplitude demodulation method can not meet the needs of high quality sensing. Phase demodulation method has the advantages of high sensitivity and high accuracy in demodulation of phase information. In recent years, it has attracted wide attention at home and abroad. The research progress of phase demodulation in ϕ-OTDR system is reviewed. Demodulation methods based on phase generated carrier (PGC), 3×3 coupler and digital coherent input-quadrature are introduced respectively. The advantages and disadvantages of these methods are simply analyzed.
2019, 43(1): 75-78.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.015
Abstract:
In order to cut off the Q-switched pulse trailing and improve the electro-optical efficiency, an exciting mode of synchronous modulation in a mechanical Q-switched radio frequency (RF) excited waveguide CO2 laser was proposed. The effects of synchronous modulation signal on the tail length of Q-switched pulse, pulse width, peak power and electro-optical efficiency were studied experimentally. The results show that, when the cut-off time of synchronous modulation signal is -80μs, the tail length of modulation Q-switched pulse is the shortest of 23μs. The electro-optical efficiency is the highest of 3% when the non-excitation duration of synchronous modulation signal is 800μs. The excitation mode of synchronous modulation can effectively cut off the pulse tail and keep the pulse width at the same time, and improve the peak power and electro-optical efficiency.
In order to cut off the Q-switched pulse trailing and improve the electro-optical efficiency, an exciting mode of synchronous modulation in a mechanical Q-switched radio frequency (RF) excited waveguide CO2 laser was proposed. The effects of synchronous modulation signal on the tail length of Q-switched pulse, pulse width, peak power and electro-optical efficiency were studied experimentally. The results show that, when the cut-off time of synchronous modulation signal is -80μs, the tail length of modulation Q-switched pulse is the shortest of 23μs. The electro-optical efficiency is the highest of 3% when the non-excitation duration of synchronous modulation signal is 800μs. The excitation mode of synchronous modulation can effectively cut off the pulse tail and keep the pulse width at the same time, and improve the peak power and electro-optical efficiency.
2019, 43(1): 79-82.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.016
Abstract:
In order to overcome the problem of the electronic bottleneck in the traditional arbitrary waveform generation method, the technology type, characteristics and application background of the radio frequency arbitrary waveform based on microwave photonics were analyzed. A triangular waveform generation with frequency doubling based on parallel Mach-Zehnder modulator was adopted, and the theoretical analysis and simulation verification were carried out. The root mean square error was introduced to evaluate the output signal and the ideal waveform. The results show that, the triangle wave signal of 20GHz can be generated by 10GHz driving signal. The root mean square error is 0.038, which means the output signal is in good agreement with the ideal signal. Compared with other methods, the method can generate frequency doubling triangle wave, and the signal waveform agrees well with the theoretical waveform. It has guiding significance for the future generation of radio frequency arbitrary waves based on microwave photonics.
In order to overcome the problem of the electronic bottleneck in the traditional arbitrary waveform generation method, the technology type, characteristics and application background of the radio frequency arbitrary waveform based on microwave photonics were analyzed. A triangular waveform generation with frequency doubling based on parallel Mach-Zehnder modulator was adopted, and the theoretical analysis and simulation verification were carried out. The root mean square error was introduced to evaluate the output signal and the ideal waveform. The results show that, the triangle wave signal of 20GHz can be generated by 10GHz driving signal. The root mean square error is 0.038, which means the output signal is in good agreement with the ideal signal. Compared with other methods, the method can generate frequency doubling triangle wave, and the signal waveform agrees well with the theoretical waveform. It has guiding significance for the future generation of radio frequency arbitrary waves based on microwave photonics.
2019, 43(1): 83-87.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.017
Abstract:
The serious adulteration of the rubber accelerator 2-mercaptobenzothiazole (MBT) will lead to the failure quality of rubber products. Aiming at this problem, a method which uses terahertz time-domain spectroscopy (THz-TDS) was proposed for quantifying the effective content of MBT. The absorption characteristic spectrum of the mixture of MBT and polyethylene in 0.3THz~1.4THz was obtained by terahertz transmission measurement. A MBT quantitative detection model based on least squares-support vector regression (LS-SVR) was proposed. LS-SVR model was compared with partial least squares model and support vector regression model respectively. The results show that, the root mean square errors of the model prediction sets are 1.1330%, 2.5583% and 2.3869% respectively. The quantitative model of LS-SVR can achieve better results with higher accuracy and better stability. This study provides a new fast and effective method for quantitative detection of MBT.
The serious adulteration of the rubber accelerator 2-mercaptobenzothiazole (MBT) will lead to the failure quality of rubber products. Aiming at this problem, a method which uses terahertz time-domain spectroscopy (THz-TDS) was proposed for quantifying the effective content of MBT. The absorption characteristic spectrum of the mixture of MBT and polyethylene in 0.3THz~1.4THz was obtained by terahertz transmission measurement. A MBT quantitative detection model based on least squares-support vector regression (LS-SVR) was proposed. LS-SVR model was compared with partial least squares model and support vector regression model respectively. The results show that, the root mean square errors of the model prediction sets are 1.1330%, 2.5583% and 2.3869% respectively. The quantitative model of LS-SVR can achieve better results with higher accuracy and better stability. This study provides a new fast and effective method for quantitative detection of MBT.
2019, 43(1): 88-92.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.018
Abstract:
In order to obtain the engineering constants of T800/QY9511 composites, by using finite element software ABAQUS and taking laser line source as force source, the process of pulse laser acting on the surface of the material and stimulating ultrasonic waves propagating inside the material was simulated. And the waveform was extracted from the center of excitation, 5 individual wave velocities were obtained. According to Christoffel theory of elasticity, the engineering constants were calculated. The results show that, compared with the real value, the average error of the numerical solution of elastic modulus is 1.56%. The mean error of Poisson ratio is 2.98%. The error of shear modulus numerical solution is 1.4%. Laser ultrasonic method is feasible and accurate in measuring the engineering constants of composite materials. It provides the basis for measuring relevant parameters in laboratory and engineering application.
In order to obtain the engineering constants of T800/QY9511 composites, by using finite element software ABAQUS and taking laser line source as force source, the process of pulse laser acting on the surface of the material and stimulating ultrasonic waves propagating inside the material was simulated. And the waveform was extracted from the center of excitation, 5 individual wave velocities were obtained. According to Christoffel theory of elasticity, the engineering constants were calculated. The results show that, compared with the real value, the average error of the numerical solution of elastic modulus is 1.56%. The mean error of Poisson ratio is 2.98%. The error of shear modulus numerical solution is 1.4%. Laser ultrasonic method is feasible and accurate in measuring the engineering constants of composite materials. It provides the basis for measuring relevant parameters in laboratory and engineering application.
2019, 43(1): 93-97.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.019
Abstract:
In order to measure the concentration of alcohol gas in the drunk drivers' breath more accurately and quantitatively, the bi-spectrum laser remote sensing detection method was used to detect the concentration of alcohol gas and water vapor at the same time, and the dilution coefficient of the alcohol gas in the vehicle was simultaneously obtained. The inversion algorithm of alcohol concentration and water vapor concentration was carried out. The dilution coefficient was calculated theoretically and the absorption spectrum was verified by experiments. The spectrum absorption characteristics of alcohol gas and water vapor were obtained. The results show that, the laser wavelength are determined to be 1392nm and 1412nm. The method can eliminate moisture interference and obtain the dilution coefficient of alcohol gas, which can more accurately and quantitatively measure the concentration of alcohol in exhaled gas.
In order to measure the concentration of alcohol gas in the drunk drivers' breath more accurately and quantitatively, the bi-spectrum laser remote sensing detection method was used to detect the concentration of alcohol gas and water vapor at the same time, and the dilution coefficient of the alcohol gas in the vehicle was simultaneously obtained. The inversion algorithm of alcohol concentration and water vapor concentration was carried out. The dilution coefficient was calculated theoretically and the absorption spectrum was verified by experiments. The spectrum absorption characteristics of alcohol gas and water vapor were obtained. The results show that, the laser wavelength are determined to be 1392nm and 1412nm. The method can eliminate moisture interference and obtain the dilution coefficient of alcohol gas, which can more accurately and quantitatively measure the concentration of alcohol in exhaled gas.
2019, 43(1): 98-102.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.020
Abstract:
In order to improve the precision and efficiency of sparse optical phased array, 1×16 optical phased array was designed based on silicon-on-insulator(SOI) platform by using the structure of spaced cosine distribution of output waveguides. Combining the effective refractive index method and 2-D finite difference beam propagation method, the far-field intensity distribution was simulated. The results show that, the side lobe suppression ratio decreases to 41.46% from 89.72%, and the full width at half maximum of the main lobe is compressed to 0.81° from 1.20°. This design method can significantly suppress the grating lobes and further compress the main lobe, and has a promising future in the field of beam deflection, such as robot obstacle avoidance, pilotless, target detection and so on.
In order to improve the precision and efficiency of sparse optical phased array, 1×16 optical phased array was designed based on silicon-on-insulator(SOI) platform by using the structure of spaced cosine distribution of output waveguides. Combining the effective refractive index method and 2-D finite difference beam propagation method, the far-field intensity distribution was simulated. The results show that, the side lobe suppression ratio decreases to 41.46% from 89.72%, and the full width at half maximum of the main lobe is compressed to 0.81° from 1.20°. This design method can significantly suppress the grating lobes and further compress the main lobe, and has a promising future in the field of beam deflection, such as robot obstacle avoidance, pilotless, target detection and so on.
2019, 43(1): 103-108.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.021
Abstract:
In order to reduce the noise in laser Doppler velocimetry signal, the method that Gaussian white noise was added to the simulated laser Doppler velocimetry signal was used. The high frequency coefficient zeroing method and the wavelet threshold denoising method were adopted for denoising after wavelet layering. The simulation analysis and experimental verification were carried out. The results show that, the high frequency coefficient zeroing method after wavelet layering can improve the signal-to-noise rate to get smooth graph signals and achieve an ideal denoising effect. The result is helpful to improve the accuracy of signal detection in laser Doppler velocimetry system.
In order to reduce the noise in laser Doppler velocimetry signal, the method that Gaussian white noise was added to the simulated laser Doppler velocimetry signal was used. The high frequency coefficient zeroing method and the wavelet threshold denoising method were adopted for denoising after wavelet layering. The simulation analysis and experimental verification were carried out. The results show that, the high frequency coefficient zeroing method after wavelet layering can improve the signal-to-noise rate to get smooth graph signals and achieve an ideal denoising effect. The result is helpful to improve the accuracy of signal detection in laser Doppler velocimetry system.
2019, 43(1): 109-114.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.022
Abstract:
In order to reduce the noise introduced to speech signal by a laser Doppler vibrometer during the measurement of sound, the method of deep recurrent neural network(DRNN) speech signal denoising was adopted. The speech signal collected from laser Doppler measurement system was denoised. By using the deep recurrent neural network with 1 layer~3 layers and 1024 neurons per layer, the speech signals with signal-to-noise ratio from -6dB to 6dB were processed. After theoretical analysis and experimental verification, the results show that, as the number of layers increases, the quality of speech signals has risen to 8dB~12dB in many evaluation indexes. DRNN can effectively denoise the speech signals collected by laser Doppler acoustic system. The research is of practical significance for improving the quality of speech signals.
In order to reduce the noise introduced to speech signal by a laser Doppler vibrometer during the measurement of sound, the method of deep recurrent neural network(DRNN) speech signal denoising was adopted. The speech signal collected from laser Doppler measurement system was denoised. By using the deep recurrent neural network with 1 layer~3 layers and 1024 neurons per layer, the speech signals with signal-to-noise ratio from -6dB to 6dB were processed. After theoretical analysis and experimental verification, the results show that, as the number of layers increases, the quality of speech signals has risen to 8dB~12dB in many evaluation indexes. DRNN can effectively denoise the speech signals collected by laser Doppler acoustic system. The research is of practical significance for improving the quality of speech signals.
2019, 43(1): 115-118.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.023
Abstract:
In order to solve the problem of beam quality decline induced by asymmetrical pumping and cooling of traditional conductive cooling lasers, one laser pumping structure with symmetrical pumping and cooling was adopted. Combined with direct coating film on laser rod end face, one miniature conductive cooling laser was designed and tested experimentally. The results show that, the output laser energy is more than 100mJ, with the laser pulse repetition of 5Hz. The laser pulse width is 9.18ns, and the energy instability is better than 8%. The laser works steadily under high and low temperature or vibration circumstance. The symmetrically-pumped conductive cooling laser has advantages of simple structure, high energy and good beam quality. It is very suitable for miniature airborne laser rangefinders.
In order to solve the problem of beam quality decline induced by asymmetrical pumping and cooling of traditional conductive cooling lasers, one laser pumping structure with symmetrical pumping and cooling was adopted. Combined with direct coating film on laser rod end face, one miniature conductive cooling laser was designed and tested experimentally. The results show that, the output laser energy is more than 100mJ, with the laser pulse repetition of 5Hz. The laser pulse width is 9.18ns, and the energy instability is better than 8%. The laser works steadily under high and low temperature or vibration circumstance. The symmetrically-pumped conductive cooling laser has advantages of simple structure, high energy and good beam quality. It is very suitable for miniature airborne laser rangefinders.
2019, 43(1): 119-124.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.024
Abstract:
In order to solve the defects of traditional maximum 2-D entropy segmentation algorithm, a large amount of calculation, more time consumption, and so on, a maximum 2-D entropy segmentation method based on the improved genetic algorithm was proposed. By improving the mutation operating mode of the genetic algorithm, the speed of the genetic algorithm to find maximum 2-D entropy segmentation threshold was improved, and then image segmentation by using the segmentation algorithm was accelerated.Through theoretical analysis and simulation experiments, the results show that, the running time of the modified model is compressed to 0.95s, which is far lower than the traditional maximum 2-D entropy segmentation method. The modified segmentation method improves the segmentation efficiency and ensures the accuracy of image segmentation.
In order to solve the defects of traditional maximum 2-D entropy segmentation algorithm, a large amount of calculation, more time consumption, and so on, a maximum 2-D entropy segmentation method based on the improved genetic algorithm was proposed. By improving the mutation operating mode of the genetic algorithm, the speed of the genetic algorithm to find maximum 2-D entropy segmentation threshold was improved, and then image segmentation by using the segmentation algorithm was accelerated.Through theoretical analysis and simulation experiments, the results show that, the running time of the modified model is compressed to 0.95s, which is far lower than the traditional maximum 2-D entropy segmentation method. The modified segmentation method improves the segmentation efficiency and ensures the accuracy of image segmentation.
2019, 43(1): 125-130.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.025
Abstract:
In order to solve the problem that the real-time performance of the laser cutting visual identity system was poor in the recognition of large and multi-target images, and the recognition rate of targets with deflection angle was low or even zero, niche genetic algorithm was used to study the large-surface multi-target matching recognition algorithm. Theoretical analysis and experimental verification were carried out. The results show that, whether the target is rotating or not, the algorithm can reach recognition rate of 100%. The computation time of the algorithm is 5 times~10 times faster than that of the traditional algorithm. The algorithm has good practicability in identifying multiple targets with rotation angle.
In order to solve the problem that the real-time performance of the laser cutting visual identity system was poor in the recognition of large and multi-target images, and the recognition rate of targets with deflection angle was low or even zero, niche genetic algorithm was used to study the large-surface multi-target matching recognition algorithm. Theoretical analysis and experimental verification were carried out. The results show that, whether the target is rotating or not, the algorithm can reach recognition rate of 100%. The computation time of the algorithm is 5 times~10 times faster than that of the traditional algorithm. The algorithm has good practicability in identifying multiple targets with rotation angle.
2019, 43(1): 131-136.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.026
Abstract:
In order to provide a visual automatic design method for the design optimization of laser transmitting telescopes, by using Matlab simulation technology, A simulation platform of laser transmitting telescope based on an inverted telescope system structure was constructed. Theoretical analysis and experimental verification of the laser transmitting telescope were carried out. By setting the key structural parameters of the laser resonator and the lens combination of the inverted telescope system, 2-D laser intensity distribution, 3-D laser intensity distribution and 3-D structure of laser beam before and after launch were achieved. The relationship between laser beam waist and the defocus value of the combined lens was simulated. The results show that the waist radius is from 0.073nm to 12.202mm after laser transformation at wavelength of 550nm. The divergence angle changes from 0.275°to 0.00164°. Laser divergence angle is successfully compressed. The simulation process of the platform is visual and intuitive. The optimum structure of laser transmitting telescope can be automatically optimized according to the need. The simulation platform provides a new method for the automatic visual design of laser transmitting telescopes.
In order to provide a visual automatic design method for the design optimization of laser transmitting telescopes, by using Matlab simulation technology, A simulation platform of laser transmitting telescope based on an inverted telescope system structure was constructed. Theoretical analysis and experimental verification of the laser transmitting telescope were carried out. By setting the key structural parameters of the laser resonator and the lens combination of the inverted telescope system, 2-D laser intensity distribution, 3-D laser intensity distribution and 3-D structure of laser beam before and after launch were achieved. The relationship between laser beam waist and the defocus value of the combined lens was simulated. The results show that the waist radius is from 0.073nm to 12.202mm after laser transformation at wavelength of 550nm. The divergence angle changes from 0.275°to 0.00164°. Laser divergence angle is successfully compressed. The simulation process of the platform is visual and intuitive. The optimum structure of laser transmitting telescope can be automatically optimized according to the need. The simulation platform provides a new method for the automatic visual design of laser transmitting telescopes.
2019, 43(1): 137-141.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.027
Abstract:
In order to eliminate inter symbol interference caused by strong scattering in ultraviolet communication, one delay decision equalization algorithm based on least mean square-maximum likelihood estimation (LMS-MLE) with channel estimation was adopted. The theoretical analysis and simulation verification were carried out. The appropriate decision delay depth was selected to adjust the LMS adaptive filter tap coefficient for channel tracking, and to obtain a new channel estimation vector. Finally, the optimal sequence output was obtained by using the MLE equalization algorithm. The results show that, the algorithm can obviously improve the performance of ultraviolet communication system. Without increasing the complexity, the performance is close to the optimal MLE equilibrium algorithm. And the channel tracking can be achieved. The optimal delay of the algorithm in ultraviolet (UV) communication is 20. This result is helpful for improving the performance of UV communication and engineering implementation of MLE equalizer.
In order to eliminate inter symbol interference caused by strong scattering in ultraviolet communication, one delay decision equalization algorithm based on least mean square-maximum likelihood estimation (LMS-MLE) with channel estimation was adopted. The theoretical analysis and simulation verification were carried out. The appropriate decision delay depth was selected to adjust the LMS adaptive filter tap coefficient for channel tracking, and to obtain a new channel estimation vector. Finally, the optimal sequence output was obtained by using the MLE equalization algorithm. The results show that, the algorithm can obviously improve the performance of ultraviolet communication system. Without increasing the complexity, the performance is close to the optimal MLE equilibrium algorithm. And the channel tracking can be achieved. The optimal delay of the algorithm in ultraviolet (UV) communication is 20. This result is helpful for improving the performance of UV communication and engineering implementation of MLE equalizer.
2019, 43(1): 142-146.
doi: 10.7510/jgjs.issn.1001-3806.2019.01.028
Abstract:
In order to better understand the characteristics and to extend the applications of Gaussian beams, based on the basic characteristics of Gaussian beam, the expressions for power in bucket, power density on the target and brightness were deduced. The normalized parameters were calculated and compared for some specific conditions. Various questions intending to be mixed in actual applications were analyzed. The analytical results are helpful for the design and applications of laser systems.
In order to better understand the characteristics and to extend the applications of Gaussian beams, based on the basic characteristics of Gaussian beam, the expressions for power in bucket, power density on the target and brightness were deduced. The normalized parameters were calculated and compared for some specific conditions. Various questions intending to be mixed in actual applications were analyzed. The analytical results are helpful for the design and applications of laser systems.
