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2017
Volume: 44 Issue 3
38 Article(s)
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Beam Transmission and Control
Wave-Front Characteristics of Amplification Configuration with Two-Pulse Bidirectional Propagating
Wei Haobo, Wei Xiaofeng, Wang De′en, Zhang Xiaolu, Yuan Qiang, Xue Qiao, Zhang Xin, Yang Ying, Zhao Junpu, Dai Wanjun, and Hu Dongxia
A two-pulse bidirectional propagating amplification configuration, which employs two laser pulses to propagate along a main amplifier in two directions of symmetric space and amplifies the two-pulse, can effectively increase the extraction efficiency for the stored energy in the amplifier, and has great application valA two-pulse bidirectional propagating amplification configuration, which employs two laser pulses to propagate along a main amplifier in two directions of symmetric space and amplifies the two-pulse, can effectively increase the extraction efficiency for the stored energy in the amplifier, and has great application value in the field of inertial confinement fusion laser driver. When we build the equivalent optical path, the wave-front distortion superposition process of the two laser pulses in the process of propagation amplification is derived, and the numerical simulation is carried out with the data measured by the Shenguang-Ⅲ host device. The results indicate that the wave-front shapes of the two laser pulses in the bidirectional propagating amplification configuration are different. The wave-front aberration mainly concentrates in low frequency range. Moreover, the wave-front distortions of the output laser pulse and the laser pulse from the pinhole of spatial filter which is with three-pass and four-pass amplification are large. Thus, the wave-front aberration must be compensated and controlled to ensure the quality of output beam and the beam pass through the spatial filter pinhole. These conclusions will provide theoretical guidance for the design of wave-front control scheme of two-pulse bidirectional propagating amplification configuration..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 305001 (2017)
Biomedical Photonics and Laser Medicine
Dose-Effect Relationship of ZnPc-PDT on Tumor Cells In Vitro
Yang Man, Xing Liyun, Gao Weidong, and Gu Yueqing
We investigated the dose-effect relationship of photosensitizer ZnPc in photodynamic therapy (ZnPc-PDT) in killing the U87 MG cells and provided reference for rational administration of ZnPc. The proliferation of U87 MG cells was determined by MTT (thiazolyl blue tetrazolium bromide) tests. The effect of ZnPc concentraWe investigated the dose-effect relationship of photosensitizer ZnPc in photodynamic therapy (ZnPc-PDT) in killing the U87 MG cells and provided reference for rational administration of ZnPc. The proliferation of U87 MG cells was determined by MTT (thiazolyl blue tetrazolium bromide) tests. The effect of ZnPc concentration, laser power density, exposure time, oxygen content and tissue thickness on the proliferation was investigated. Then the production of singlet oxygen during ZnPc-PDT was determined by the DPBF probe and DCFH-DA reactive oxygen species assay kit. The cell morphology and the proportion of cell death was observed by an inverted microscope. The results show that U87 MG cell viability changes different parameters setting after ZnPc-PDT, and we can get a good ZnPc-PDT effect by adjusting the parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 307001 (2017)
Fiber Optics and Optical Communication
Analysis of Parameters of Integrated Optical System of Ranging,Imaging and Communication
Zhang Yalin, Fu Qiang, Jiang Huilin, Wang Chao, and Han Long
In recent years, space debris is increasing with the development of space technology, and has a serious effect on the safety operation of on-orbit spacecraft. Therefore, it is urgent to detect and remove the space debris. With the increasing demand for space debris detection, the space debris detection system graduallyIn recent years, space debris is increasing with the development of space technology, and has a serious effect on the safety operation of on-orbit spacecraft. Therefore, it is urgent to detect and remove the space debris. With the increasing demand for space debris detection, the space debris detection system gradually develops to a integrated and multifunctional system. An integrated optical system of ranging, imaging and communication is proposed. The maximum detection range of imaging tracking and the received power of ranging communication are analyzed, and the optimum parameters of the integrated optical system are chosen. The results show that the best obscure ratio is in the range of 0.144-0.172, the transmittivity of secondary mirror film is in the range of 0.3-0.6, and the optimal transmittivity is 0.462. This study provides a reference for the study on the integrated system used for space debris detection..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 306001 (2017)
Temperature Demodulation Method for Distributed Fiber Raman Temperature Measurement
Zhang Mingjiang, Li Jian, Liu Yi, Zhang Jianzhong, Li Yunting, Huang Qi, Liu Ruixia, and Yang Shuaijun
To improve the measuring speed and the measuring accuracy of the distributed fiber Raman temperature measurement system, a temperature demodulation method of self-compensation for fiber loss and fiber dispersion is proposed, and the experimental verification is carried out. The loss between Stokes backscattering signalTo improve the measuring speed and the measuring accuracy of the distributed fiber Raman temperature measurement system, a temperature demodulation method of self-compensation for fiber loss and fiber dispersion is proposed, and the experimental verification is carried out. The loss between Stokes backscattering signal and anti-Stokes backscattering signal is modified by the proposed method, the calibration processing for the entire sensing fiber before temperature measurement is avoided, and the system operating time is reduced. The dispersion compensation shift algorithm is applied to correct the position of the Stokes backscattering signal. The intensity of Stokes backscattering signal can be obtained at the same position of the anti-Stokes backscattering signal, which eliminates the influence of fiber dispersion on temperature demodulation and improves the accuracy of temperature measurement. The experimental results indicate that the temperature fluctuation is declined from 9.01 ℃ to 0.57 ℃ when the fiber sensing distance is 5.8 km, and the temperature accuracy is optimized from 5.50 ℃ to 0.87 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 306002 (2017)
Thermal Control Technology for Optical Antenna in Geostationary Orbit Space Satellite-Borne Laser Communication
Liu Bailin, Zhou Zuoxin, Li Jian, and Tan Liying
As the key component of space laser communication systems, optical antenna is required to have good stability and uniformity for temperature field. The thermal control technology for temperature field of antenna is facing more challenge owing to the large antenna aperture and the complex fusion of external heat flux inAs the key component of space laser communication systems, optical antenna is required to have good stability and uniformity for temperature field. The thermal control technology for temperature field of antenna is facing more challenge owing to the large antenna aperture and the complex fusion of external heat flux in geostationary orbit space. According to the characteristics of antenna configuration and the discipline of external heat flux variation, the long-term fine stability control for the stability and the uniformity of antenna temperature field is achieved in large diameter optical communication when we combine the space efficient heat protection technology with the optical mirror aided thermal control technology, which is based on the design for optical, mechanical and thermal design. The proposed method is verified by thermal test. Experiment results show that in the case that the antenna is taken strategy to avoid direct sun, the duration is up to 14.3 h/d, which satisfies the request for antenna temperature. The temperature is controlled stably in the range of 21.4-26.2 ℃. The thermal difference of the primary mirror itself is not larger than 1.3 ℃, and the thermal difference between the primary mirror and the secondary mirror is not larger than 3.8 ℃. These results are larger than the required indexes of stability and uniformity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 306003 (2017)
Holography and Information Processing
Incoherent Digital Holographic Microscopic Imaging Based on Michelson Interferometer
Zhang Wenbin, Liu Yafei, Li Deyang, Ma Fengying, Gong Qiaoxia, and Du Yanli
The incoherent digital holographic microscopic imaging system based on the Michelson interferometer can be used to obtain the hologram of object under illumination of incoherent light. The incoherent digital holographic microscopic imaging system based on the Michelson interferometer is studied theoretically and experiThe incoherent digital holographic microscopic imaging system based on the Michelson interferometer can be used to obtain the hologram of object under illumination of incoherent light. The incoherent digital holographic microscopic imaging system based on the Michelson interferometer is studied theoretically and experimentally. The point spread function of the system in the recording process has been calculated according to the scalar diffraction theory, and the specific expressions of lateral magnification and reconstruction distance of the system are deduced. A experimental light path of incoherent digital holographic microscopic imaging system based on the Michelson interferometer is built, and a CCD is used to record the holograms. A clear reconstruction image is obtained without conjugate image and zero-order image by the generalized phase-shifting digital holographic interferometry and via the angular spectrum algorithm. Furthermore, the incoherent holographic microscopic imaging of a resolution board and onion epidermal cells have been implemented, which proves the feasibility of the system. The imaging experiment of the resolution board shows that a lateral resolution as high as 512 lp/mm can be obtained. The system is able to present the characteristics of the three-dimensional structure of objects, which is verified by the imaging of the micron cleansing brush fur..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 309001 (2017)
Laser Devices and Laser Physics
Light Collecting Characteristics of Nd∶YAG Ceramic Condenser Chamber Unilaterally Pumped by Laser Stacked Array
Liu Chang, Yu Jin, and Fan Zhongwei
For the requirements of compact and simplified solid laser gain module structure design, a model of Nd∶YAG crystal rod unilaterlly pumped by laser diode (LD) stacked array is built. The absorbed light distribution within the Nd∶YAG crystal rod in ceramic condenser chamber is simulated with the TracePro software. The inFor the requirements of compact and simplified solid laser gain module structure design, a model of Nd∶YAG crystal rod unilaterlly pumped by laser diode (LD) stacked array is built. The absorbed light distribution within the Nd∶YAG crystal rod in ceramic condenser chamber is simulated with the TracePro software. The influences of condenser chamber′s shape, crystal rod′s radius and doping concentration of Nd3+ on the light collecting efficiency and the gain distribution uniformity are studied. The research shows that the light collecting efficiency changes approximately linearly with the cross-sectional area of the condenser chamber. A Nd∶YAG crystal rod with radius of 2 mm and Nd3+ doping concentration of 0.5% (atom fraction) can obtain near fundamental mode oscillation output with 1.0 mm spot radius. The distribution of absorbed pumping light is more uniform when the ratio of the uniform pumping area radius of crystal rod to the U-shape condenser chamber radius is about 0.5. With the discussed structure, the light collecting efficiency reaches 65%, while the gain distribution uniformity is better than 0.65 in the LD stacked array unilaterally pumped Nd∶YAG crystal structure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301001 (2017)
Analysis on Cooling Performance of Compact Mid-Infrared Solid State Laser
Zhang Kuo, Yu Deyang, He Yang, Pan Qikun, Chen Fei, and Li Dianjun
Cooling compact mid-infrared solid state laser is difficult for its compact structure and temperature restriction of laser pump module. A laser cooling system is proposed using forced convection cooling technique, thermo electric cooling technique and heat pipe technique. A finite element model for the laser cooling syCooling compact mid-infrared solid state laser is difficult for its compact structure and temperature restriction of laser pump module. A laser cooling system is proposed using forced convection cooling technique, thermo electric cooling technique and heat pipe technique. A finite element model for the laser cooling system is built with the COMSOL software. Temperature data is experimentally measured by sensors. The validity of this model is verified with the experimentally measured data. The effect of cooling system parameters, such as fan speed and heat pipe, on temperature distribution is numerically computed with the finite element model at different environmental temperatures. The results indicate that increasing the fan speed and installing the heat pipe are beneficial to improving the cooling effect, and the cooling effect is more obvious with the increase of environment temperature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301002 (2017)
Solar Directly Pumped 1064 nm Laser Amplifier
Wang Yu, Zhao Changming, Yang Suhui, Zhang Haiyang, and Guan Zhe
The solar directly pumped 1064 nm laser amplifier is designed, and the solar pumped laser amplification is realized. The laser amplifier uses Fresnel lens and metal conical cavity as sunlight gathering system. The laser materials are Nd∶YAG and Nd/Cr∶YAG disk. The theory of solid-state laser amplification is analyzed. The solar directly pumped 1064 nm laser amplifier is designed, and the solar pumped laser amplification is realized. The laser amplifier uses Fresnel lens and metal conical cavity as sunlight gathering system. The laser materials are Nd∶YAG and Nd/Cr∶YAG disk. The theory of solid-state laser amplification is analyzed. The sunlight gathering system is simulated by tracePro, and the pump power density at surface of the laser material is calculated. Based on the physical properties and optical features of Nd∶YAG and Nd/Cr∶YAG, the internal temperature distribution of the laser material is simulated with LASCAD to verify the feasibility of the design. When the solar radiation power density is 900 W/m2 and the maximum seed laser power is 300 mW, the maximum laser output power is 475.1 mW. Experimental data of different sunlight gathering systems and laser materials are analyzed comparatively to provide direction for further improvement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301003 (2017)
Design and Research of Side Lighted Fiber of Laser Backlight Source in Liquid Crystal Display
Zhao Zhitong, Zhang He, Zou Yonggang, and Ma Xiaohui
The method of side-surface process of fiber is designed and studied to make the fiber side lighting, then the laser source of multi-spot structure required by liquid crystal display backlight module is obtained. The effects of different depths, areas and geometrical structures of hole on the optical field of the fiber The method of side-surface process of fiber is designed and studied to make the fiber side lighting, then the laser source of multi-spot structure required by liquid crystal display backlight module is obtained. The effects of different depths, areas and geometrical structures of hole on the optical field of the fiber during the side-surface process are simulated and analyzed. The light field is obtained that the uniformity of the maximum luminous intensity of each light spot is within 5% field..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301004 (2017)
Structural Optimization and Fabrication of 850 nm Vertical-Cavity Surface-Emitting Laser
Feng Yuan, Hao Yongqin, Wang Xiantao, Liu Guojun, Yan Changling, Zhang Jiabin, Li Zaijin, and Li Yang
According to the principle of distributed Bragg reflector (DBR), the quantum well (QW) and DBR structures are optimized. By employing Crosslight computer simulation software, the reflectance spectrum and the QW gain spectrum of vertical cavity surface emitting laser (VCSEL) are simulated, and the QW composition, width According to the principle of distributed Bragg reflector (DBR), the quantum well (QW) and DBR structures are optimized. By employing Crosslight computer simulation software, the reflectance spectrum and the QW gain spectrum of vertical cavity surface emitting laser (VCSEL) are simulated, and the QW composition, width and pairs of the DBR are determined. The high quality epitaxial wafers of 850 nm top-emitting VCSEL are grown by the molecular beam epitaxy technology and processed into devices. The experimental results indicate that the lasing wavelength from the In0.075Ga0.925As/Al0.35Ga0.65As QW structure with well width of 5 nm is approximately 840 nm at room temperature, and the theoretical results obtained by Ocean Optics Spectra Suite software show that the central wavelength of the spectrum is near to 850 nm at room temperature. The results verify the correctness of the design..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301005 (2017)
Methane Pressure Detection Based on Fourier Transform Infrared Spectroscopy
Li Zhiyong, Tan Rongqing, Huang Wei, Ye Qing, Li Hui, and Han Gaoce
Since the carbon atoms from the hydrocarbon gases are the unique resource of carbon deposition in alkali vapor laser, precise measurement for the gas pressure in a stand-off way will be helpful to depict the carbon contamination phenomenon quantitatively. Based on the Fourier transform infrared spectroscopy, a method fSince the carbon atoms from the hydrocarbon gases are the unique resource of carbon deposition in alkali vapor laser, precise measurement for the gas pressure in a stand-off way will be helpful to depict the carbon contamination phenomenon quantitatively. Based on the Fourier transform infrared spectroscopy, a method for detecting the methane pressure is presented. In the method, the peak (3.369 μm) on the right side of the main peak is chosen to be the characteristic peak. The effects of the alkali cell tilt on the accuracy are also researched. The experiments results show that the maximum deviations are 0.055 kPa and 0.057 kPa when only methane is in the cell or the volume ratio of methane and helium filled in the cell is 1∶3. The deviations will be higher than 0.075% if the tilt angle is higher than 0.0035 rad. The measurement accuracy of the methane pressure can characterize the carbon contaminating problems, and provide a reference for investigating the mechanism of carbon contamination in the alkali lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 301006 (2017)
Laser Manufacturing
Effect of Laser-Fused Assisted Nitriding on Structure and Property of Inconel 690 Alloy Tube
Yang Jiaoxi, Jin Yanpeng, Li Ziyang, Zhang Guangrui, Jia Wuming, and Chang Wanqing
In order to improve the corrosion resistance and wear resistance of Inconel 690 alloy tube surface, the laser-fused assisted nitriding treatment to alloy tube surface is investigated. The microstructure, phase composition, microhardness and corrosion resistance of samples after treatment are tested and analyzed. The reIn order to improve the corrosion resistance and wear resistance of Inconel 690 alloy tube surface, the laser-fused assisted nitriding treatment to alloy tube surface is investigated. The microstructure, phase composition, microhardness and corrosion resistance of samples after treatment are tested and analyzed. The results show that the laser nitriding layer is mainly composed of CrN and γ phases which has good metallurgical quality without defects such as cracks and pores and the microstructures uniformly distribute with fine grains. The laser-fused assisted nitriding layers have the highest microhardness of 253 HV. After the laser-fused assisted nitriding treatment, the alloy tube has better corrosion resistance to Cl- ions with slight reduction of corrosion resistance to OH- ions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302001 (2017)
Dual Beam Fiber Laser Welding Characteristics of Cross-Type Joint
Ma Guolong, Li Liqun, Chen Yanbin, and Zhao Heng
Study of welding the special cross-type joint is carried out by dual beam fiber laser welding technique. The effects of beam configuration and heat input on the dual beam laser welding characteristics of cross-type joint are systematically studied from weld formation, mechanical property and microstructure. The resultsStudy of welding the special cross-type joint is carried out by dual beam fiber laser welding technique. The effects of beam configuration and heat input on the dual beam laser welding characteristics of cross-type joint are systematically studied from weld formation, mechanical property and microstructure. The results show that the cross-type joint can be successfully fabricated by dual beam laser welding method, and the joint with good weld formation and satisfied mechanical property can be obtained. The joining zone is completely fused when the heat input exceeds 120 kJ/m. The weld formation of tandem dual beam laser welding is superior to that of side-by-side dual beam laser welding. The tensile strength of joint increases with the increasing of heat input. With the same heat input, the tensile strength of tandem beam configuration is bigger than that of side-by-side beam configuration. The tensile strength reaches 96.5% of the base metal with heat input about 140 kJ/m. The microhardness of remelting zone is higher than that of non-remelting zone, which is attributed to the reason that more acicular δ ferrites are generated in weld fusion line after remelting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302002 (2017)
Effect of Energy Ratio on Dual Beam Laser Welding Characteristics
Ma Guolong, Li Liqun, and Chen Yanbin
Effect of energy ratio on weld formation and energy efficiency in the dual beam welding process was systematically studied. Molten pool behaviors under different energy ratios were observed in real time by the high speed video system. Influence mechanism of the energy ratio on dual beam laser welding characteristics waEffect of energy ratio on weld formation and energy efficiency in the dual beam welding process was systematically studied. Molten pool behaviors under different energy ratios were observed in real time by the high speed video system. Influence mechanism of the energy ratio on dual beam laser welding characteristics was also revealed. Results show that the weld penetration depth increases and then decreases as the energy ratio increases, while the weld width shows the opposite variation tendency. The minimum penetration depth and maximum width are obtained at the energy ratio of 50/50. Energy efficiency is significantly different from each other with different energy ratios. The maximum energy efficiency is 32.7% at the energy ratio 20/80, while the minimum is 27.8% at the energy ratio 50/50. Molten pool size is also affected by the energy ratio. Molten pool length increases first and then decreases, and the molten pool width always decreases with the increase of energy ratio. The effect of energy ratio on dual beam laser welding characteristics is mainly attributed to the variation of keyhole and molten pool flow pattern in the welding process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302003 (2017)
Quality Diagnosis of Joints in Laser Brazing Based on Principal Component Analysis-Support Vector Machine Model
Cheng Liyong, Mi Gaoyang, Li Shuo, Hu Xiyuan, and Wang Chunming
Based on the principal component analysis-support vector machine (PCA-SVM) model, one method is proposed to predict the joint morphology with the near infrared radiation signal. The correlation between the change laws of signals and the weld formation morphology is investigated and the optimization of process parameterBased on the principal component analysis-support vector machine (PCA-SVM) model, one method is proposed to predict the joint morphology with the near infrared radiation signal. The correlation between the change laws of signals and the weld formation morphology is investigated and the optimization of process parameters is realized. Six kinds of characteristic parameters of signals in time domain are extracted and the principal component analysis is carried out to obtain the comprehensive evaluation index of joint morphology. Based on the input characteristics of signals， the classification prediction is done by using the support vector machine. The results show that, the near infrared radiation signals can reflect the change of weld state during the welding process, the characteristic changes of different defects have great difference, and the clear recognition exists. The proposed prediction model can accurately identify weld appearance with accuracy up to 96.6%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302004 (2017)
Effects of Processing Parameters of Ultra-Fast Laser on Surface Coloring of Stainless Steel
Wu Yonghua, Yang Baoping, and Kang Xianmin
Experiment study on surface coloring of 304 stainless steel is carried out by using picosecond laser. The mechanism of the coloring on stainless steel surface by picosecond laser is analyzed, and the surface color model is established. The influence of the laser processing parameters such as scanning line spacing, scanExperiment study on surface coloring of 304 stainless steel is carried out by using picosecond laser. The mechanism of the coloring on stainless steel surface by picosecond laser is analyzed, and the surface color model is established. The influence of the laser processing parameters such as scanning line spacing, scanning speed and pulse energy on coloring effect is studied，respectively. Experimental results show that changes of line spacing, scanning speed and pulse energy have a significant impact on the coloring effect，and good color can be obtained with the parameters range of scanning speed from 90 μm/s to 300 μm/s, line spacing from 0.001 mm to 0.01 mm, and single pulse energy from 60 mJ/cm2 to 140 mJ/cm2. The effects of three parameters on coloring have similar impact. Based on the experiment, the relationship between the parameters of picosecond laser and the CIE L*a*b* color model is obtained. Finally, the color aging contrast test of the samples after coloring is carried out. Experimental results show that the chromatic aberrations ΔE of laser coloring samples with different aging times are very small, which indicate that all samples are very similar. And they have good anti-aging effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302005 (2017)
Analysis and Experimental Investigation of Laser Induced Damage of Optics
Wang Hongxiang, Shen Lu, Li Chengfu, Bai Hua, and Zhou Yan
The influences of surface impurities, etching time, subsurface defects and the width to depth ratio on the laser damage threshold of fused silica optics in the traditional grinding and polishing process are systematically analyzed by laser damage experiments. Results show that the laser damage thresholds are 21.6 J/cm2The influences of surface impurities, etching time, subsurface defects and the width to depth ratio on the laser damage threshold of fused silica optics in the traditional grinding and polishing process are systematically analyzed by laser damage experiments. Results show that the laser damage thresholds are 21.6 J/cm2 and 11.28 J/cm2 for wiped and non-wiped optics, respectively. The laser damage threshold is greatly reduced by the surface impurities, while the laser damage threshold at the defect area is significantly lower than that at no defect area. The increase of the etching time increases the surface roughness and defect size of the workpiece, which leads to a significant decrease in the laser damage threshold of the optics, so a reasonable choice of chemical etching time is required. The incident light field can be modulated by subsurface defects, resulting in local area reflected light, scattered light and incident light superimposed on each other, eventually leading to laser damage of optical material. The width to depth ratio of the scratch increases with the etching time, which can gradually weaken the scratch on the light field modulation, thereby the probability of occurrence of laser damage for fused silica optics is reduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302006 (2017)
Femtosecond Laser Processing of Polycrystalline Diamond Micro-Structure Array
Huang Jianheng, Liang Guowen, Li Ji, and Guo Baoping
Femtosecond laser micromachining is a kind of cold working technology, which can overcome the influence of thermal effect. The advantage of this technology in micromachining of the hard brittle materials with high melting point is very obvious, because the edges of the processed materials are very neat and precise. A pFemtosecond laser micromachining is a kind of cold working technology, which can overcome the influence of thermal effect. The advantage of this technology in micromachining of the hard brittle materials with high melting point is very obvious, because the edges of the processed materials are very neat and precise. A processing technique of polycrystalline diamond micro-structure by femtosecond laser is proposed to fabricate an X-ray source micro-structure array anode, which consists of metallic target and polycrystalline diamond. The micromachining parameters of polycrystalline diamond by femtosecond laser were studied experimentally. The effect of laser pulse energy, focus objective and scanning number on the morphology and dimension of ablated area was analyzed in detail. Finally, high quality polycrystalline diamond micro-structure arrays with a width of 20 μm and a depth of 45 μm were fabricated by femtosecond laser, and the maximum power density of permissable electron beam on its surface is 12 W/mm2. The polycrystalline diamond micro-structure array can be used for X-ray source with a micro-structure array anode, and can be utilized in X-ray phase contrast imaging for large field of view..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302007 (2017)
Ultra-Narrow Gap Laser Wire Filling Welding Forming Defects of 5083 Aluminum Alloy Thick Plate
Xie Yufasheng, Huang Jian, Wang Wei, Wang Huan, and Hua Xueming
To solve the problems of poor fusion tendency and pore defect occurred during the process of laser welding of 5083 aluminum alloy thick plate, a fiber laser is used in the ultra-narrow gap wire filling welding test for 5083 aluminum alloy with the thick of 20 mm. The effects of laser power, welding speed and wire feed To solve the problems of poor fusion tendency and pore defect occurred during the process of laser welding of 5083 aluminum alloy thick plate, a fiber laser is used in the ultra-narrow gap wire filling welding test for 5083 aluminum alloy with the thick of 20 mm. The effects of laser power, welding speed and wire feed rate on poor fusion tendency and pore defect are analyzed. The results show that increasing laser power, decreasing welding speed and decreasing wire feed rate are beneficial to reducing poor fusion tendency. Pore defects can be reduced when we reduce laser power or welding speed, and decrease first and then increase while the wire feed rate is increasing continually. The laser wire filling welding for 5083 aluminum alloy with ultra-narrow gap groove (the depth is 17 mm) is achieved with optimal parameters, i.e., distance between laser and filler wire of +1 mm, welding speed of 0.42 m/min, laser power of 3.8 kW, wire feed rate of 3.5 m/min and defocus distance of +20 mm. The poor fusion is eliminated and the porosity is reduced to 0.25%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302008 (2017)
Temperature Field of Molten Pool and Microstructure Property in Laser Melting Depositions of Ti6Al4V
Li Liqun, Wang Jiandong, Wu Chaochao, Zhang Min, and Zhao Weigang
Ti6Al4V alloy thin wall is prepared by using laser melting deposition, and the influences of process parameters on the size stability of molten pool and microstructure growth characteristics of deposited layers are studied. The temperature field of molten pool and cooling rate of melt under different process conditionsTi6Al4V alloy thin wall is prepared by using laser melting deposition, and the influences of process parameters on the size stability of molten pool and microstructure growth characteristics of deposited layers are studied. The temperature field of molten pool and cooling rate of melt under different process conditions are calculated based on finite element simulation method. The results show that the molten pool size varies significantly with the change of heat dissipation condition of substrate in the process of melting deposition of the first few layers. The heat input of each layer is optimized, which can realize the accurate control of stability of molten pool size. Compared with laser power, the influence of scanning speed on directional growth characteristic and grain size of deposited layer is more remarkable. With the change of scanning speed, the microstructure of deposited layer can easily transform from columnar crystal to equiaxial crystal. Under these experimental conditions, the directional growth columnar crystal can not be formed unless the cooling rate of molten pool is higher than 135.3 ℃/s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302009 (2017)
Parameter Nondimensionalization in Laser Direct Metal Deposition Formation of Inconel 625 and Its Influence on Single Track Geometric Morphology
Li Jinbao, Shang Shuo, Sun Youzheng, Guo Kuaikuai, and Liu Changsheng
In order to standard different parameters in the laser direct metal deposition (LDMD) formation technology, the experiment of LDMD formation of Inconel 625 spherical alloy powders and the nondimensionalization of the formation parameters are conducted, and the working diagram with the contact angle as an evaluation parIn order to standard different parameters in the laser direct metal deposition (LDMD) formation technology, the experiment of LDMD formation of Inconel 625 spherical alloy powders and the nondimensionalization of the formation parameters are conducted, and the working diagram with the contact angle as an evaluation parameter of geometric morphology is obtained. The relationship between the geometric morphology of single track deposited layer and the process parameters is discussed. The results show that, when the ratio of characteristic energy is between 0.5 and 0.7, the deposited layer shows a relatively smooth oval because of incomplete melting of powder and less energy redundancy. Feeding rate is the primary factor to control the height of deposited layers. When the feeding rate is constant, the laser power has a great influence on the depth of molten pools..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302010 (2017)
Characteristics of Interdendritic Residual Austenite in Laser Cladding of High Hardness Iron-Based Coating
Li Linqi, Yao Chengwu, Huang Jian, Feng Kai, and Li Zhuguo
The high hardness iron-based coating is prepared by using laser cladding, in which the average hardness is about 775 HV and no cracks are found. The results characterizing the coating microstructure show that the coating consists of uniform and tiny cellular dendrites, martensite distributes in primary dendrites, residThe high hardness iron-based coating is prepared by using laser cladding, in which the average hardness is about 775 HV and no cracks are found. The results characterizing the coating microstructure show that the coating consists of uniform and tiny cellular dendrites, martensite distributes in primary dendrites, residual austenite is precipitated in the interdendritic region, and carbides distribute dispersively in the residual austenite substrate. The segregation of molybdenum, chromium, wolfram and niobium exists in the interdendritic region, but carbon distributes uniformly in the cladding layer. Many stacking faults are observed in the residual interdendritic austenite, and matensite separats out in the stacking faults intensive area..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302011 (2017)
Effect of Small Diameter Side-Blown Gas Flow on Fiber Laser Welding of Medium and Heavy Plate
Xing Mengqi, Li Zhuguo, Sun Junhao, and Zhang Wang
With the assistance of the small diameter side-blown gas, the fiber laser welding of SUS 304 stainless steel sample is performed. The behaviors of keyholes, molten pools and metallic vapor are observed by using the high-speed photography equipment under the background light source and the fusion depth and formation of With the assistance of the small diameter side-blown gas, the fiber laser welding of SUS 304 stainless steel sample is performed. The behaviors of keyholes, molten pools and metallic vapor are observed by using the high-speed photography equipment under the background light source and the fusion depth and formation of welds are also analyzed. The results indicate that, when the laser power, welding speed, defocusing amount, position and angle of gas jet nozzle, and other welding parameters are constant, the fusion depth of welds increases with the increment of small diameter side-blown gas flow. The small diameter side-blown gas can open the keyholes obviously, maintain the stability of the keyholes, and also enlarge the area of the molten pool. The gas flow value has a great influence on the formation of welds. Without the small diameter side-blown gas, the uniformly-distributed weld formation with lots of the spatters is achieved. When the gas flow value is small, the uniformly-distributed weld formation with few spatters is achieved. When the gas flow value is too large, the spatters are few and the weld formation is poor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 302012 (2017)
Materials and Thin Films
Experimental Research on Ge-doped Diamond-like Carbon Films Prepared by Double Laser Beams Deposition
Cheng Yong, Lu Yimin, Huang Guojun, Guo Yanlong, Wei Shangfang, and Chu Hua
Double laser beams deposition method for preparing doped thin film is designed. An excimer nanosecond laser and a femtosecond laser are used to ablate the graphite and germanium targets, respectively. The laser parameters of the excimer nanosecond laser keeps unchanged, and the repetition frequency of the femtosecond lDouble laser beams deposition method for preparing doped thin film is designed. An excimer nanosecond laser and a femtosecond laser are used to ablate the graphite and germanium targets, respectively. The laser parameters of the excimer nanosecond laser keeps unchanged, and the repetition frequency of the femtosecond laser changes from 0 to 500 Hz. Then the Ge-doped diamond-like carbon films with increased germanium concentration are prepared. The results of tests show that, with the improvement of germanium content, the refractive index of the Ge-doped diamond-like carbon film increases slightly, and the extinction coefficient increases 7.3 times. The surface-hardness of the films decreases by 41.3% linearly, while the inner-stress in the films reduces by 78.1% nonlinearly and tend to a steady value. The results of the fastness test show that the increasing of the germanium content can enhance the adhesion of the films on the germanium substrates, but reduce their corrupt-resistant against the circumstance. Because of the strong expansibility of the research method, the research results can not only offer the experiment base for the designs of doped diamond-like carbon films or multiple doped diamond-like carbon films in different fields, but also offer a new means of preparing other doped films for different purposes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 303001 (2017)
Development of Heat Radiation Filter Film for Ultraviolet Curing System
Fu Xiuhua, Fan Jiachen, Zhang Jing, Xiong Shifu, Chen Zhihang, and Yang Yongliang
In order to reduce the heat radiation of ultraviolet (UV) curing system, based on the optical thin-film theory, with HfO2, AlF3 and Cr as coating materials, and by use of the reflection and absorption combined structure, the filter film system with high reflection in the UV band and high absorption in visible-near infrIn order to reduce the heat radiation of ultraviolet (UV) curing system, based on the optical thin-film theory, with HfO2, AlF3 and Cr as coating materials, and by use of the reflection and absorption combined structure, the filter film system with high reflection in the UV band and high absorption in visible-near infrared band is designed. The soundness of the thin film is improved by coating Al film as the transition layer between the substrate and the film system. After the optimization of process parameters, the filter film with average reflectivity of 90.6% in 220-400 nm wave band and average absorptivity of 92.4% in 420-2000 nm wave band is developed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 303002 (2017)
Study and Fabrication of Narrow-Band Filter Film in Methane Gas Detection and Recognition System
Xiong Shifu, Fu Xiuhua, Liu Dongmei, Zhang Jing, and Fan Jiachen
Based on the theory of optical thin film and the characteristics of optical materials, by combining with the film system design software and using the principle of splitting technique, the design of double-sided film system is achieved, which solves the problem that the single-sided thin film is too thick and with an eBased on the theory of optical thin film and the characteristics of optical materials, by combining with the film system design software and using the principle of splitting technique, the design of double-sided film system is achieved, which solves the problem that the single-sided thin film is too thick and with an excessive stress. With the inverse analysis method, the experimental test results are inversed. With the research of the sensitivity distribution of film layer, the causes of the errors are analyzed, and the thickness of sensitive layers of film system is precisely controlled with different monitoring methods. The final spectral test results of prepared filter films show that the transmissivity of single point is 93.7% at the wavelength of 3.31 μm, the full width of passband at half maximum is 49 nm, and the mean transmissivity at wavebands of 1~3.2 μm and 3.4~5 μm is 0.17% , which can meet the operational requirements of the system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 303003 (2017)
Impact of Carbon Contamination Cleaning Technologies on Reflectivity of Extreme Ultraviolet Lithography Optics
Wang Yi, Lu Qipeng, and Gao Yunguo
The carbon contamination of extreme ultraviolet lithography system will degrade the reflectivity of multilayer. On the premise of guaranteeing the performances of optics，how to choose the carbon cleaning process is an important project. By analyzing the principle of various cleaning methods process theory, it is revealThe carbon contamination of extreme ultraviolet lithography system will degrade the reflectivity of multilayer. On the premise of guaranteeing the performances of optics，how to choose the carbon cleaning process is an important project. By analyzing the principle of various cleaning methods process theory, it is revealed that the influences of different technologies on the reflectivity of multilayer mainly are film oxidation, etching and surface roughness degradation. On the base of finite difference time domain and total integrated scattering theory, the relation between various influence factors and reflectivity of multilayer is studied. Results show that film oxidation and surface roughness degradation are main factors that result in decrease of the reflectivity of multilayer, while the influence for etching is minor. Based on the above analysis results, both radio frequency hydrogen plasma and atomic hydrogen cleaning technologies will not reduce the performances of optics and can be adopted as prior options, while the carbon contamination at the surface of optics is removed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 303004 (2017)
Influence of Annealing Treatment on Structure Defects of Nd, Y∶SrF2 Laser Crystals
Liu Rongrong, Zhu Jiqian, Liu Junfang, Wang Jingya, Su Liangbi, Tang Fei, Jiang Dapeng, Qian Xiaobo, and Wu Qinghui
Under vacuum condition, the Nd, Y∶SrF2 laser crystals were annealed at high temperatures from 1060 ℃ to 1100 ℃. The X-ray double crystal rocking curve, the bending strength, the stress distribution, and the wave-front aberration spectrum of Nd, Y∶SrF2 crystals were measured before and after annealing. The results show Under vacuum condition, the Nd, Y∶SrF2 laser crystals were annealed at high temperatures from 1060 ℃ to 1100 ℃. The X-ray double crystal rocking curve, the bending strength, the stress distribution, and the wave-front aberration spectrum of Nd, Y∶SrF2 crystals were measured before and after annealing. The results show that the crystallization properties, the bending strength, the stress distribution and the optical homogeneity of the crystals are improved by annealing at a high temperature. When the annealing temperature is 1080 ℃ and the annealing time is 36 h , the crystal is obtained with the best integrated performance, and hence the annealing temperature of 1080 ℃ and the annealing time of 36 h are the optimal annealing parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 303005 (2017)
Measurement and Metrology
Phase Retrieval Method Based on Liquid Crystal on Silicon Tunable-Lens
Cheng Hong, Lü Qianqian, Zhang Wenjun, Deng Huilong, and Gao Yaoli
In traditional phase retrieval method based on transport of intensity equation (TIE), there are problems of slow speed and low accuracy caused by moving the object to be measured or CCD in the process of light intensity images acquisition. In order to solve these problems, a new method using the liquid crystal on silicIn traditional phase retrieval method based on transport of intensity equation (TIE), there are problems of slow speed and low accuracy caused by moving the object to be measured or CCD in the process of light intensity images acquisition. In order to solve these problems, a new method using the liquid crystal on silicon (LCOS) as tunable-lens for phase retrieval is proposed in this paper. Firstly, the phase distribution images with different focal lengths are loaded in a LCOS to make it realize the function of tunable-lens. Then the light intensity images of different defocusing distances are collected in the same imaging plane by the designed system in this paper. Finally, the phase information is obtained by solving the TIE. With this method, different defocusing images can be formed by changing the phase distribution image loaded in the LCOS, avoiding the errors caused by mechanical shift. The correctness and effectiveness of the proposed phase retrieval method are verified by the simulation and experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 304001 (2017)
Measurement of Atmospheric Turbulence Parameters on Airborne Platform Based on Differential Image Motion Method
Zhang Lei, Zhao Xin, Tong Shoufeng, Li Bo, and Jiang Huilin
Atmospheric turbulence parameters are the important bases to evaluate the effect of atmospheric channel on space laser communication system performance. According to the motion characteristic of airborne platform, the atmospheric turbulence parameter stratified measurement experiments are carried out at different altitAtmospheric turbulence parameters are the important bases to evaluate the effect of atmospheric channel on space laser communication system performance. According to the motion characteristic of airborne platform, the atmospheric turbulence parameter stratified measurement experiments are carried out at different altitudes in Jagdaqi area with the differential image motion method, and these experiments are combined with Shack-Hartmann sensor and pointing, acquisition, tracking servo units. Results show that the daytime atmospheric turbulence intensity in this region reduces with the increase of altitude, and random fluctuation of atmospheric turbulence intensity is superimposed on the changing trend under the condition of Kolmogorov turbulence. The range of top layer altitude of atmospheric capping inversion layer is 2.2-2.8 km. At the altitude of 3.5 km, the atmospheric coherence length varies from 10 cm to 26 cm. The study provides an important reference for the performance analysis of airborne laser communication system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 304002 (2017)
CMM Spatial Coordinate Correction Method Based on Laser Tracer Multistation Measurement
Chen Hongfang, Zheng Bowen, Shi Zhaoyao, Sun Yanqiang, Long Changyu, and Yang Zaihua
Coordinate measuring machine (CMM) is a high efficiency precision measurement system for coordinate measurement technology. As the development of ultra-precision machining technology, the requirement of the measuring precision of CMM is getting higher and higher. Considering the weak rigid body state of CMM in the procCoordinate measuring machine (CMM) is a high efficiency precision measurement system for coordinate measurement technology. As the development of ultra-precision machining technology, the requirement of the measuring precision of CMM is getting higher and higher. Considering the weak rigid body state of CMM in the process of measurement, this paper proposes a CMM spatial coordinate correction method based on multistation measurement of laser tracer. Firstly, the laser tracer multistation measurement system is set up. Then, the coordinate of measuring point of CMM is corrected by using the high precision interference length of the laser tracer. Finally, the measuring spatial coordinate of CMM is corrected by using the trilinear interpolation method. The simulation experimental results show that the average of the standard deviation of the standard sphere diameter obtained by proposed spatial coordinate correction method is 0.098 μm, which is smaller than 0.118 μm, the average of the standard deviation directly measured by CMM. The results verify that the proposed method can effectively improve the spatial coordinate accuracy of CMM..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 304003 (2017)
Rapid Communications
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 315001 (2017)
Remote Sensing and Sensor
Photonic Crystal Fiber High Sensitivity Magnetic Field and Temperature Sensor Based on Surface Plasma Resonance Effect and Defect Coupling
Zhu Chenghao, Tan Ce, Wang Yan, Gao Yuan, Dong Bicheng, Ma Hanlin, and Liu Hai
A new photonic crystal fiber sensor based on surface plasma resonance (SPR) effect and defect coupling mechanism is proposed. Two air holes of photonic crystal fiber cladding in the sensor are filled with magnetic fluid material. One hole is coated with metallic thin film on inner layer，and the diameter of the other hoA new photonic crystal fiber sensor based on surface plasma resonance (SPR) effect and defect coupling mechanism is proposed. Two air holes of photonic crystal fiber cladding in the sensor are filled with magnetic fluid material. One hole is coated with metallic thin film on inner layer，and the diameter of the other hole is changed to form defect. By analyzing the relationship among refractive index, temperature and magnetic field of magnetic fluid, the simultaneous measurement for temperature and magnetic field can be achieved. Results show that the coupling resonance peak and the SPR loss peak are blue shifted as temperature increasing and red shifted as magnetic field increasing. The temperature sensitivity of the coupling resonance peak and the SPR loss peak can reach -1.338 nm/℃ and -1.575 nm/℃ respectively, and the magnetic field sensitivity of them is 4.333 μm/T and 2.816 μm/T respectively. The proposed sensor not only has a high sensitivity, but also can achieve accurate measurement for magnetic field and temperature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 310001 (2017)
Calculation Method for Stiffness Coefficient of Compliant Cylinder in Fiber-Optic Interferometric Vibration Sensor
Gao Wenzhi, Chen Jiandong, Ge Zhaobin, Sun Wei, Fu Qunjian, Lang Jinpeng, Chang Tianying, and Cui Hongliang
In this paper, the principle of fiber-optic interferometric compliant cylinder sensor is analyzed from the perspective of energy distribution, and the compound compliant cylinder calculation formula of the equivalent stiffness coefficient is given. Finite element analysis method is used to simulate the natural frequencIn this paper, the principle of fiber-optic interferometric compliant cylinder sensor is analyzed from the perspective of energy distribution, and the compound compliant cylinder calculation formula of the equivalent stiffness coefficient is given. Finite element analysis method is used to simulate the natural frequency of the compound compliant cylinder, and the simulation results show that the distance from wrapped position of the fiber-optic to the intermediate inertia oscillator should be 5 mm. In the experiment, the natural frequency measurement method is used to indirectly calculate the equivalent compliant cylinder stiffness coefficient. The experimental results from the measurement of three different compliant cylinder sensors show that the proposed method can be used as the basis of the calculation of the compliant stiffness coefficient..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 310002 (2017)
Reviews
High-Speed Visible Light Communication Based on LED
Chi Nan, Lu Xingyu, Wang Can, and Zhou Yingjun
By the year of 2018, the popularizing rate of common light emitting diode (LED) will reach 80%. The visible light communication (VLC) technology based on LED is expected to provide new scheme for the implementation of high-speed VLC. Researchers at home and aboard have studied technologies of modulation, coding or equaBy the year of 2018, the popularizing rate of common light emitting diode (LED) will reach 80%. The visible light communication (VLC) technology based on LED is expected to provide new scheme for the implementation of high-speed VLC. Researchers at home and aboard have studied technologies of modulation, coding or equalization and multiplexing, materials and chips in order to broaden the modulation bandwidth, improve the transmission rate and increase the transmission distance. The international research hotspots are analyzed and discussed, including technologies of carrier amplitude-phase modulation, orthogonal frequency division multiplexing modulation with adaptive bit power loading, hardware or software pre-equalization and post-equalization, and the principle and the performance of novel optical material. The latest researches are summarized in order to offer a reference for the future research of VLC..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 300001 (2017)
Spectroscopy
Spectral Time Evolution Behavior of Laser Induced Steel Target Plasma
Fu Jie, Guo Xiqing, Zhao Tianzhuo, Lian Fuqiang, and Fan Zhongwei
In order to improve the quality of laser induced breakdown spectroscopy, we used a time-resolved spectrometer to collect steel target plasma emission spectra. The relationship between the intensity of spectral lines and the delay time was discussed. It demonstrates that both the spectral intensity and background intensIn order to improve the quality of laser induced breakdown spectroscopy, we used a time-resolved spectrometer to collect steel target plasma emission spectra. The relationship between the intensity of spectral lines and the delay time was discussed. It demonstrates that both the spectral intensity and background intensity decay exponentially with the delay time. Spectral intensity of atoms decreases faster in the first 4 μs but the atoms′ spectral lines exist for a longer time. However, ions′ spectral lines exist for shorter. Acquisition delay has different influence on signal to noise ratios of different spectral lines. The best delays of Mn I 403.08 nm ,Cr I 428.97 nm, Cr Ⅱ 458.82 nm, Fe I 430.79 nm and Fe Ⅱ 503.57 nm spectra obtained are 8, 2, 0, 2, 4 μs, respectively. The double lines method and the Boltzmann plot method were used to calculate the plasma temperature， and the Saha-Boltzmann equation was used to calculate the electron density. It is verified that the spectral signal meets the local thermal equilibrium state in the acquisition time range of 0-10 μs..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 311001 (2017)
Terahertz Technology
Progress of Terahertz Radiometry and International Comparison
Deng Yuqiang, Sun Qing, Yu Jing, Xu Nan, and Lin Yandong
The wide application of terahertz technology demands accurate and traceable measurement of terahertz radiometry. The first international terahertz power comparison took place under the guideline of the consultative committee for photometry and radiometry of the international committee for weights and measures. A highlyThe wide application of terahertz technology demands accurate and traceable measurement of terahertz radiometry. The first international terahertz power comparison took place under the guideline of the consultative committee for photometry and radiometry of the international committee for weights and measures. A highly absorptive terahertz radiometer is fabricated for the comparison and the uncertainty of terahertz measurement are analyzed and experimentally investigated, for realizing the terahertz measurement accurately and guaranteeing the internationally equivalence and mutual recognition of Chinese terahertz measurements. Also, for confirming the measurement accuracy and uncertainty analysis of the terahertz radiometer, a terahertz radiometers with specular reflection is constructed, and the comparison measurements with the highly absorptive terahertz radiometer is performed. The self-made terahertz radiometer is used in the first international terahertz comparison, and excellent agreement is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 44, Issue 3, 314001 (2017)
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