Journals >Chinese Journal of Lasers
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2015
Volume: 42 Issue 3
47 Article(s)
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Biomedical Photonics and Laser Medicine
Semi-Empirical Model for Biological Tissue Diffuse Reflectance Measurement with Small Aperture
Ma Zhao, Liu Ying, and Lian Ge
Optical diffuse spectroscopy is crucial in quick and non-invasive measurement of biological tissues. However, the lack of exact analytical solution limits its applications. A semi-empirical formula of diffuse reflectance measured via small apertures is elaborated on the basis of Monte Carlo method, and a function relatOptical diffuse spectroscopy is crucial in quick and non-invasive measurement of biological tissues. However, the lack of exact analytical solution limits its applications. A semi-empirical formula of diffuse reflectance measured via small apertures is elaborated on the basis of Monte Carlo method, and a function relation between the reflectivity and the aperture, relative refractive index is created. Based on this semi-empirical formula, the inversion of optical parameters of turbid biological media is performed and its application range is analyzed. Compared to the expression of diffusion approximation, the proposed analytical formula is mathematically simple and suitable for the measurement of radiation field near the light source..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 304001 (2015)
Laser Manufacturing
Effect of Laser Shock Processing on Mechanical Properties and Mesostructures of AZ31 Magnesium Alloy
Zhang Qinglai, Wang Rong, Zhang Bingxin, Qian Yang, Chen Jun, Hong Yanxin, and Wu Tiedan
In order to study the effect of laser shock processing (LSP) on mechanical properties of magnesium alloy, the room and thermal (300 ℃ ) tensile stress-strain curves of AZ31 alloy sheets are investigated by using electronic universal high temperature tensile machine and Nd: glass laser with wavelength of 1064 nm and pulIn order to study the effect of laser shock processing (LSP) on mechanical properties of magnesium alloy, the room and thermal (300 ℃ ) tensile stress-strain curves of AZ31 alloy sheets are investigated by using electronic universal high temperature tensile machine and Nd: glass laser with wavelength of 1064 nm and pulse width of 20 ns. The results show that the room and thermal tensile strength of AZ31 alloy are improved by LSP. The maximum thermal flow stress of laser shocked specimens is obviously higher than that of untreated. However, the double- sided single LSP results in the reduction of mechanical properties at room temperature. And the spallation phenomenon which extends along subsurface occurs on fracture of the shocked samples. Effect of the residual compressive stress, mesostructures, surface morphologies and roughness on mechanical properties of magnesium alloy by LSP are discussed and analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303001 (2015)
Study on Laser Surfi-Sculpt of GMW2 Autobody Sheet Steel for Carbon Fiber Reinforced Polymer/Steel Dissimilar Joint
Tan Xianghu, Shan Jiguo, Tang Lei, and Cheng Wuzhu
To solve the problem of shrinkage voids in carbon fiber reinforced polymer (CFRP)/steel dissimilar joint，the fiber laser surfi-sculpt on the GMW2 autobody sheet steel is adopted. The effects of laser power, scanning speed, scanning length and scanning repeats on the width and height of protrusion are systematically invTo solve the problem of shrinkage voids in carbon fiber reinforced polymer (CFRP)/steel dissimilar joint，the fiber laser surfi-sculpt on the GMW2 autobody sheet steel is adopted. The effects of laser power, scanning speed, scanning length and scanning repeats on the width and height of protrusion are systematically investigated. The laser surfi-sculpt process is studied by high speed visual detection system. The results show that the protrusion width is the same as the molten pool width. Increasing the laser power or decreasing the scanning speed will cause the increase of molten pool width, leading the protrusion width to increase. While scanning length and scanning repeats do not affect the molten pool width, so they have no effect on protrusion width. The protrusion height is determined by vaporization pressure, surface tension and hydrodynamic pressure. With the laser power increasing, the vaporization pressure increases and the surface tension decreases. Namely the driving force for the liquid metal flow to the behind of molten pool increases. So the appropriate increase of laser power is beneficial for protrusion to grow taller. When the laser power is too high, a large number of spatters will be produced, leading to the protrusion height instable. With the increase of scanning speed, vaporization pressure, surface tension and hydrodynamic pressure will change. There is a competition between driving force and resistance, which leads the protrusion height first to increase and then decrease. With the increase of scanning length, the horizontal component of vaporization pressure and the driving force increase, leading to the increase of protrusion height..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303002 (2015)
Effect of Cu on Properties of FeCr Laser Cladding Layer and Machining Vibration Suppressing in Side Milling
Zhao Yanhua, Sun Jie, and Li Jianfeng
Aiming at the processing difficulties of laser cladding remanufacturing layer of large centrifugal pipeline compressor blade, cladding damping alloy formula and repaired layer milling process theory are investigated. The laser cladding repaired layers are prepared by FeCr alloy and Cu mixed powder on KMN steel substratAiming at the processing difficulties of laser cladding remanufacturing layer of large centrifugal pipeline compressor blade, cladding damping alloy formula and repaired layer milling process theory are investigated. The laser cladding repaired layers are prepared by FeCr alloy and Cu mixed powder on KMN steel substrate. The microstructure, phase constitution, hardness and wear resistance of the repaired layer are investigated by scanning electron microscope, X-ray diffractometer, energy dispersive spectrometer, Vickers digital micro-hardness tester, sliding wear tester and optical profiler. Vibration signal is collected during side milling process of repaired layer. The impact of Cu on machining vibration and surface roughness is investigated. The results show that, the grain size decreases dramatically and the microstructure of repaired layer is refined with the Cu content increasing. The hardness and wear resistance of coatings with Cu are improved significantly. Machining vibrations of repaired layer with Cu are obviously reduced, and the chatter is effectively avoided occurring..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303003 (2015)
Study on Dimensional Accuracy of Typical Geometric Features Manufactured by Selective Laser Melting
Yang Xiongwen, Yang Yongqiang, Liu Yang, and Wang Di
In order to investigate dimensional accuracy of geometric features manufactured by selective laser melting (SLM) and to provide design references for SLM to manufacture metal parts directly, several typical geometric features such as thin walls, sharp corners, cylinders, circular holes, square holes, etc are designed. In order to investigate dimensional accuracy of geometric features manufactured by selective laser melting (SLM) and to provide design references for SLM to manufacture metal parts directly, several typical geometric features such as thin walls, sharp corners, cylinders, circular holes, square holes, etc are designed. Then SLM equipment DiMetal-100 is employed and 316L stainless steel powders are used to manufacture these typical geometric features under the condition of optimized process parameters. It is shown that laser spot restraint, step effect, powder adhesion and laser deep penetration are the main factors which affect dimensional accuracy of parts and affect manufacturing ability of SLM. The manufacturing ability of SLM and the dimensional accuracy of typical geometric features by SLM is studied. It puts forward some preliminary design rules suitable for SLM, which provides a reference for innovative design of products..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303004 (2015)
Study on Kerf Roughness Differences between Line and Arc Analysis and Elimination of Laser Precision Cutting
Wang Dawei, and Gao Xifeng
In this paper, arcs on the 0.5 mm pure thick aluminum (1060) sheet is cut precisely by Nd:YAG pulse laser, to eliminate roughness differences of laser cutting stencil, the microstructure of kerf results is obtained through microscope, which provides the basis to set up the simplified mathematical model. Formulas to estIn this paper, arcs on the 0.5 mm pure thick aluminum (1060) sheet is cut precisely by Nd:YAG pulse laser, to eliminate roughness differences of laser cutting stencil, the microstructure of kerf results is obtained through microscope, which provides the basis to set up the simplified mathematical model. Formulas to estimate the kerf surface roughnesses of these arcs are presented, and the effect laws of radius size on the kerf surface roughnesses differences with the same cutting parameters are analyzed particularly. The results show that, with decreasing the radii of outside arc and inside arc, the kerf roughnesses are improved; when the radius R≤7 mm, the roughnesses of these two arcs are different significantly; when the radius R>7 mm, the differences of these roughnesses almost disappear. At last, optimizing the kerf roughnesses of all shapes by response surface method (RSM) minimize optimization and target optimization respectively to obtain the cutting parameters, the roughnesses of all shapes cut by above cutting parameters are almost same, therefore this method eliminates the linear and circular roughness differences, which is feasible and effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303005 (2015)
Research on Microstructure and Element Diffusion in YG20/45# Steel Laser Welds
Cao Xiaolian, Xu Peiquan, Cao Zhuoyue, Gou Ning, and Yu Beibei
The influence of laser welding speed on microstructure and element diffusion in YG20/45# steel laser welds are investigated using 5 kW fiber laser under the condition of no groove without filler metals. Weld appearance, microstructure and element diffusion at YG20/45# steel interface are analyzed. On the basis, the infThe influence of laser welding speed on microstructure and element diffusion in YG20/45# steel laser welds are investigated using 5 kW fiber laser under the condition of no groove without filler metals. Weld appearance, microstructure and element diffusion at YG20/45# steel interface are analyzed. On the basis, the influence of laser welding speed on the weld appearance with large coefficient of thermal expansion is discussed between dissimilar materials. The results indicate that for 2 mm base materials, YG20/45# steel welded joint with well metallurgy can be obtained, when the following welding parameters are used: laser power P=1.93 kW, laser scanning speed v=2.40 m/min, and defocusing amount - 8 mm; with the increase of welding heat input, WC coarsening occurs at cemented carbide/welds interface accompanied by large cracking sensitivity. The cracks are commonest in the heat affected zone of welded joint, but may also be situated in the weld metal, which deteriorates mechanical properties of welded joints. The analysis results of line scanning indicate that W、Co in cemented carbide and Fe in iron bring about mutual diffusion, making the joint reaching a favorable metallurgical combination..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303006 (2015)
Surface Micro-Dimple Effect and Electrochemical Corrosion Behaviors of AZ31B Magnesium Alloy Treated by Laser
Zhou Jianzhong, Zhong Hui, Huang Shu, Sheng Jie, Dai Lei, and Mei Yufen
In order to study the influence of laser-induced micro-dimple on electrochemical corrosion behaviors of AZ31B magnesium alloy, samples are processed with optical fiber laser to get specific microdimple. The surface profile, diameter and depth of the micro-dimple are characterized by Axio CSM 700 and the electrochemicalIn order to study the influence of laser-induced micro-dimple on electrochemical corrosion behaviors of AZ31B magnesium alloy, samples are processed with optical fiber laser to get specific microdimple. The surface profile, diameter and depth of the micro-dimple are characterized by Axio CSM 700 and the electrochemical polarization curves are investigated by electrochemical work station. The results indicate that with the increment of laser power, the depth and diameter of micro-dimple increase but ablation occurs around the micro-dimple. The diameter of micro-dimple does not change significantly while the roundness improves with the number of processing increasing. Comparing with the untreated specimen, the corrosion potentials are improved by -33, 40, 26 mV and the self-corrosion currents decrease to 91.93% , 92.09% , 91.19% with laser powers of 6, 10, 16 W respectively under the same micro-dimple density condition. A better corrosion resistance is obtained with laser power of 10 W. For the same laser power condition, the corrosion potentials are improved by 21, 40, 56 mV and the self-corrosion currents decrease to 92.22% , 92.09% , 94.05% with the micro-dimple densities of 1.5% , 2.5% , 5.0% respectively comparing with the untreated specimen. Besides, the increasing of micro-dimple density leads to a better corrosion resistance of AZ31B magnesium alloy in the density zone of the experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303007 (2015)
Microstructure and Microhardness of 4045 Aluminum Alloy Fabricated by Laser Melting Deposition
Chen Yongcheng, Zhang Shuquan, Tian Xiangjun, and Wang Huaming
Thin plate-like 4045 aluminum alloy sample is fabricated by laser melting deposition (LMD). Microstructure and microhardness of the laser melting deposition 4045 aluminum alloy before and after heat treatment are analyzed. Results indicate that a hypoeutectic microstructure comprising about 42.7% (volume fraction) of dThin plate-like 4045 aluminum alloy sample is fabricated by laser melting deposition (LMD). Microstructure and microhardness of the laser melting deposition 4045 aluminum alloy before and after heat treatment are analyzed. Results indicate that a hypoeutectic microstructure comprising about 42.7% (volume fraction) of directionally solidified Al dendrites with the primary dendrite arm spacing of approximately 22.3 μm and the secondary dendrite arm spacing of approximately 7.5 μm is developed during LMD process. The transition from columnar Al dendrites to equiaxed Al dendrites takes place at the top of the as-deposited sample. Coral-like Si develops at the bottom of the depositing layer and changes to flake -like Si at the top of the depositing layer due to the decrease of the cooling rate. Flake-like Si should be sufficiently remelted out during the subsequent layer deposition to obtain well modified coral-like Si. Coarse equiaxed Si develops at the overheated zone just below fusion line due to the spheroidizing and coarsening of coral-like Si, and the microhardness of the overheated zone is lower than that of the inner zone. Coral-like Si can be totally spheroidized after 540 ℃ isothermal heat treatment for 20 min, and Si coarsens and grows up leading to the decrease of the microhardness as the holding time extends..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303008 (2015)
Experiment of Quartz Glass Flute Precise Thinning by Femtosecond Laser
Wu Dongjiang, Zhou Siyu, Ma Guangyi, and Yao Longyuan
In order to realize the precisely thinning of flute on the surface of quartz by femtosecond laser, the line-surface ablation process means are taken to study the effects of the pulse energy on the ablation morphology of groove, and the ablation experimental research of flute with different line overlap rates δ are carrIn order to realize the precisely thinning of flute on the surface of quartz by femtosecond laser, the line-surface ablation process means are taken to study the effects of the pulse energy on the ablation morphology of groove, and the ablation experimental research of flute with different line overlap rates δ are carried out. The laser scanning confocal microscope is used to observe and analyze the depth, bottom surface roughness and other morphology features of flute. The results show that when the line overlap rate δ satisfies 40%≤ δ ≤80%, with the increase of δ, the depth and sidewall angle of flute decrease, when δ is 40%, the depth, width and sidewall angle of groove is 14.56 μm, 261.8 μm and 59.1°, respectively. The bottom surface roughness decreases as well, when δ is 80%, Ra and Rz reach the minimum of 0.19 μm and 1.23 μm, respectively. The profile fluctuation parallel to scanning speed increases at first then decreases, when δ =80%, Ra′ ≈Ra, Rz′ ≈Rz; The root mean square of bottom surface Sq decreases with the increase of δ, Sq reaches the minimum of 0.16 μm when δ is 80%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303009 (2015)
Research on Variable Reference Plane Cladding Based on Laser Processing Robot with Inside-Laser Powder Feeding
Zhu Gangxian, Shi Shihong, Fu Geyan, Shi Jianjun, Yang Shi, Meng Weidong, and Jiang Fubing
Laser cladding technology is based on horizontal reference plane at present, however, this way greatly limits its extensive applications. The substrate inclined angle of 0°~150° and continuously variable postures of coaxial powder nozzle have been achieved by changing the programming to control the laser procLaser cladding technology is based on horizontal reference plane at present, however, this way greatly limits its extensive applications. The substrate inclined angle of 0°~150° and continuously variable postures of coaxial powder nozzle have been achieved by changing the programming to control the laser processing robot adopting the technology of“hollow laser beam and interal powder feeding”. The influence rules of the substrate inclined angle on the section size and microstructure of cladding layers are investigated, and the force of molten pool is analyzed during varging the inclined angles of the substrate. The experimental results show that the powder converging behavior becomes worse with the increase of the substrate inclined angle, because reducing of powder volume into molten pool leads to decreases of the cladding layers′ height. The width of cladding layers do not show significant variations and offset first increase and then decrease. The dendrite size of the cladding layers′ top microstructure first becomes thick and then thin gradually and the growth direction of typical columnar crystal tilts with the substrate inclined angle. The process basis is provided for laser cladding, repairing and forming on variable reference plane by the inside-laser powder feeding way..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303010 (2015)
Embedded Machine Vision Online Measure-Control System of Defocusing Amount in Laser Cladding Forming
Wang Tao, Fu Geyan, and Shi Shihong
To maintain the defocusing amount during the metal laser cladding forming experiments, the distance between the forming surface and the nozzle should be fixed. Based on optical triangle method, an embedded machine vision online measuring system for controlling the laser defocusing amount is proposed. The formula for deTo maintain the defocusing amount during the metal laser cladding forming experiments, the distance between the forming surface and the nozzle should be fixed. Based on optical triangle method, an embedded machine vision online measuring system for controlling the laser defocusing amount is proposed. The formula for designing the lens focal length of the measuring camera is deducted, and both hardware and software solutions are meanwhile presented. To process the gained pictures from the measuring camera effectively and stably, a new algorithm estimation based on molten pool gray threshold is used for programming. The output voltage from the measuring system is also integrated into the robot controlling coding which helps adjust the nozzle position automatically once the laser defocusing amount is offset. This measuring system is later verified through several metal laser cladding forming experiments to be stable and precise. By comparing the thin-wall cylinder forming parts, the surface roughness of the part made with the measuring system is much brighter and cleaner than the ones without this system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303011 (2015)
Research on Excimer Laser Etching Technology for Achieving Optical Waveguide End Face
Jia Nana, Deng Chuanlu, Pang Fufei, Gu Xin, and Wang Tingyun
Based on the excimer laser ablation principle, etching technique for achieving optical waveguide end face is proposed for application requirements of optical printed circuit backplane interconnect. With the laser etching technique, optical coupling end face can be fabricated at any position on optical printed circuit bBased on the excimer laser ablation principle, etching technique for achieving optical waveguide end face is proposed for application requirements of optical printed circuit backplane interconnect. With the laser etching technique, optical coupling end face can be fabricated at any position on optical printed circuit backplane. An excimer laser with the wavelength of 193 nm is used as the ablation light source. The laser beam is projected onto the optical waveguide for etching through a square aperture mask. The relationship among the laser energy, laser pulse times and etching depth, surface roughness has been studied experimentally. After optimizing the etching parameters, the coupling loss increase of the waveguide end face is approximate 1.3 dB after the etching process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303012 (2015)
Ag Periodic Nanostructures and Morphology Controlled by Ultraviolet-Visual Photoreduction for Surface-Enhanced Raman Scattering
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Photoreduction, especially laser-reduction, is a clean and controllable micro- and nano-fabrication method which has been applied in the field of spectroscopy, fluorescent imaging and three dimensional (3D) fabrication. The in situ reduction of Ag+ with ultraviolet nanosecond laser lithography is focused, which is muchPhotoreduction, especially laser-reduction, is a clean and controllable micro- and nano-fabrication method which has been applied in the field of spectroscopy, fluorescent imaging and three dimensional (3D) fabrication. The in situ reduction of Ag+ with ultraviolet nanosecond laser lithography is focused, which is much time-effective compared with two(multi)-photon absorption reduction. Combined with ultraviolet and visible light reduction, different sub- micron gratings with large area and different surface morphology are fabricated. The reduction mechanism based on the roles of laser reduction time is discussed, Ag+ concentration and light wavelength. The gratings compose of a large number of close-packed Ag nanoparticles which are of importance for surfaceenhanced Raman scattering. The performance of surface-enhanced Raman scattering is demonstrated by tracing naproxen..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303013 (2015)
Cladding Angle Model and Variation Law of Fe-Based Coating Fabricated by Mechanical Vibration Assisted Laser Cladding
Tao Xide, Liu Hongxi, Zhang Xiaowei, and Jiang Yehua
Fe55 alloy coating is fabricated on 45 steel surface through laser cladding assisted mechanical vibration process. The geometry morphology of cladding coating is observed by optical microscrope. Utilizing AutoCAD, geometry parameters of cladding coating height, width and cladding angle are marked to explore the effectsFe55 alloy coating is fabricated on 45 steel surface through laser cladding assisted mechanical vibration process. The geometry morphology of cladding coating is observed by optical microscrope. Utilizing AutoCAD, geometry parameters of cladding coating height, width and cladding angle are marked to explore the effects of laser specific energy, amplitude and frequency of mechanical vibration on cladding angle. By means of second- order polynomial of response surface analysis method, a function model being able to express the relationship among cladding angle, laser specific energy, amplitude and frequency is established. Results show that the cladding angle of laser cladding coating is greater when combined with mechanical vibration. Provided with the same laser specific energy and amplitude of vibration, the cladding angle under frequency of 200 Hz is larger than the one with frequency of 100 Hz, and the cladding angle reaches the minimum value when the amplitude is 0.10 mm. The calculated value of cladding angle using the least squares function models is superior to the existing geometry model by being closer to the actual measurement result..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 303014 (2015)
Laser Cladding Ni/Ni3Al Based Double Performance Materials and Internal Microstructure Analysis
Yang Jiaoxi, Wang Yanfang, and Wang Zhicheng
Ni/Ni3Al double performance coatings with good metallurgical quality are obtained through optimizing the process parameters and using multi-laser cladding. Double performance materials crack-sensitivity can be reduced effectively by changing the laser processing parameters. The generation and mechanism of cracks in theNi/Ni3Al double performance coatings with good metallurgical quality are obtained through optimizing the process parameters and using multi-laser cladding. Double performance materials crack-sensitivity can be reduced effectively by changing the laser processing parameters. The generation and mechanism of cracks in the laser processing are investigated. The microstructure, composition and phase constitution of the coatings are characterized using scaming electron microscope (SEM), X-ray diffrcaction (XRD), respectively. The results reveal that small amount phases of Al8Cr5 and Al4CrNi15 are precipitated in the single clad coating due to the dilution of Nibased alloy. Additionally, a single Ni3Al phase is produced in the coating by means of multilayer cladding, which can keep good properties of Ni3Al-based materials and perform the characteristics of double-properties materials more sufficiently. The micro-hardness testing of the coatings show that the double-properties material is able to maintain high hardness even under higher temperature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306001 (2015)
Laser Physics
Broadband Spectrum Bessel Beams Directly Output from a Photonic Crystal Fiber
Zhou Zhaoxian, Hu Minglie, Zhou Yuzhu, Li Yanfeng, and Wang Qingyue
A scheme of broadband spectrum Bessel beams directly output from a nonlinear photonic crystal fiber is designed. A femtosecond laser beam from a nonlinear polarization evolution laser system is directly coupled into a nonlinear photonic crystal fiber that is collapsed 1 mm by a fiber fusion splicer to enable the directA scheme of broadband spectrum Bessel beams directly output from a nonlinear photonic crystal fiber is designed. A femtosecond laser beam from a nonlinear polarization evolution laser system is directly coupled into a nonlinear photonic crystal fiber that is collapsed 1 mm by a fiber fusion splicer to enable the direct generation of broadband spectrum Bessel beams due to the modes coupling and coherent superposition at the collapsed district. The system operation can be achieved by all fiber without any other discrete devices. The broadband spectrum Bessel beams directly output from photonic crystal fiber have diffraction-free propagation in meter-scaled free space and are proved to have the characteristics of diffraction-free and selfheal in all spectrum..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302001 (2015)
Research on Linear Chirped Pulse Generated by Direct Phase Modulation
Tian Xiaocheng, Zhang Kun, Zhu Na, Xu Dangpeng, Zhang Rui, Zhou Dandan, Huang Zhihua, and Wang Jianjun
Linear chirped pulse generated by direct phase modulation can be used in chirped- pulse amplification system, which can produce ultrashort optical pulses with high pulse energy. The process of the linear chirped pulse generation, the amplification and transmission characteristics of the modulated pulse in fiber have beLinear chirped pulse generated by direct phase modulation can be used in chirped- pulse amplification system, which can produce ultrashort optical pulses with high pulse energy. The process of the linear chirped pulse generation, the amplification and transmission characteristics of the modulated pulse in fiber have been numerically simulated and experimentally studied. A 500 ps pulse at 0.69 nm bandwidth linear chirped pulse has been generated in experiment. A new method of generating shock ignition seed pulse is proposed. A seed pulse with high contrast is generated by modulating and compressing part of the pulse, which is verified by expriment. A stagewise pulse with 2∶1 intensity contrast after modulating and compressing a square pulse is generated to confirm the feasibility of generating stock ignition pulse using this method. This method may be used in the front end system of intertial confinement fusion (ICF) driver in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302002 (2015)
Experimental Study on High Brightness and Narrow Band of Diode Laser by Spectral Beam Combining of Grating-External Cavity
Meng Huicheng, Wu Deyong, Tan Hao, Li Jianming, Yu Junhong, and Gao Songxin
The grating-external cavity spectral beam combined is based on the wavelength selection characteristic of the grating and the feedback by external cavity and simultaneously controls each emitter of the diode laser array (DLA) to lock at different wavelengths, while forces the individual beam to overlap in the near and The grating-external cavity spectral beam combined is based on the wavelength selection characteristic of the grating and the feedback by external cavity and simultaneously controls each emitter of the diode laser array (DLA) to lock at different wavelengths, while forces the individual beam to overlap in the near and far fields. The spectral combined beam has the same beam quality as the beam of single emitter of the DLA, greatly improve the beam quality of the output beam. The conventional CM-Bar with 19 emitters is applied, The period of the CM-Bar is 500 μm and the width of emitter is 100 μm . With the maximum continuous wave (CW) injection current of 70 A, a continuous 44.90 W laser output is obtained. The beam quality of slow and fast axes after spectral beam combined are 1.52 mm·mrad and 5 mm·mrad, respectively. Electro-optic conversion efficiency of 36% is achieved. The brightness of output spot is about 36.92 MW/cm2-str, spectral widening is 3.24 nm, combining output laser coupled into 50 μm core diameter, numerical aperture (NA) of 0.22 fiber, can be used as a high-brightness laser pump source or direct diode laser source..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302003 (2015)
26 W Mid-Infrared Solid-State Laser
Han Long, Yuan Ligang, Chen Guo, Hou Tianyu, Wei Lei, He Lijie, and Wang Keqiang
A high power mid infrared (Mid-IR) laser is introduced. High frequency laser of 2.05 μm is obtained in Ho:YLF laser pumped by 1.94 μm laser, and the power of 2.05 μm laser is increased by amplifying in an endpumping schedule, finally, a high power Mid- IR laser is obtained in a OPO pumped by the 2.05 μm laser. The scheA high power mid infrared (Mid-IR) laser is introduced. High frequency laser of 2.05 μm is obtained in Ho:YLF laser pumped by 1.94 μm laser, and the power of 2.05 μm laser is increased by amplifying in an endpumping schedule, finally, a high power Mid- IR laser is obtained in a OPO pumped by the 2.05 μm laser. The schedule is cooled by water,the max power of Mid- IR laser is up to 26.9 W, the pulse width is 24.4 ns, the efficiency from 2.05 μm to Mid- IR is up to 50% , and the wavelength is varied with the different input angle. Through the experience, it is proved that a high power, high frequency and high efficiency Mid-IR laser can be realized in this method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302004 (2015)
Temperature Coefficient of High-Q Microsphere Cavity
Shang Chenglong, Tang Jun, Pi Hailong, Zhang Wei, Xie Chengfeng, Zhang Tian′en, Lei Longhai, Wang Minghuan, Guo Zebin, Zhang Binzhen, Liu Jun, Xue Chenyang, and Zhang Wendong
Optical microsphere resonant cavity has been widely researched in the field of high sensitivity sensor and optical communication because of its high Q value and minimal model volume. Optical resonance wavelength shifts are measured with temperature changes for unpackaged and encapsulated microsphere. Linear dependence Optical microsphere resonant cavity has been widely researched in the field of high sensitivity sensor and optical communication because of its high Q value and minimal model volume. Optical resonance wavelength shifts are measured with temperature changes for unpackaged and encapsulated microsphere. Linear dependence of red shift against temperature rise with high linearity is observed. The temperature cofficient is 25.6 pm/℃ for unpackaged microsphere, whereas is 4.4 pm/℃ for encapsulated one, which mostly results from ultraviolet (UV) glue′s negative thermo-optic coefficient. The thermo-optic effect is analyzed based on UV glue. The fraction of light in UV glue can be changed by the thickness of glue, and then, temperature coefficient is also changed. The temperature coefficient decreases to zero when the fraction is 0.1135, which means the depression of temperature drift as well as the realization of thermal compensation. Sensitivity of temperature is improved as fraction increases. Suppressed temperature drift, improved sensitivity, and miniaturization enables broad application potentials of whispering-gallery mode (WGM)-based sensors..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302005 (2015)
Ytterbium-Doped Nanosecond-Pulsed All-Fiber Laser Based on Dissipative Soliton Resonance and Its Frequency-Doubling
Yang Tieshan, Wang Xiuhong, Sun Ruoyu, Li Yanping, Cheng Zhaochen, Li Huihui, Shi Hongxing, Liu Jiang, and Wang Pu
A novel nanosecond-pulsed, frequency-doubled green laser at 532 nm is reported, whose fundamental light is a dissipative soliton resonance (DSR) square-shaped, nanosecond pulse, which is obtained by all-fiber ytterbium-doped laser with master-oscillator power-amplifier (MOPA) system. The ytterbium-doped fiber seed laseA novel nanosecond-pulsed, frequency-doubled green laser at 532 nm is reported, whose fundamental light is a dissipative soliton resonance (DSR) square-shaped, nanosecond pulse, which is obtained by all-fiber ytterbium-doped laser with master-oscillator power-amplifier (MOPA) system. The ytterbium-doped fiber seed laser generates stable DSR, square-shaped, nanosecond pulse by using nonlinear polarization rotation (NPR) modelocked technology. The pulse width of the fiber laser can be stably turned from 3 ns to 40 ns by just changing the pump power. After one stage non polarization-maintained ytterbium-doped fiber and two stages polarizationmaintained ytterbium-doped fiber amplification, the final output power is 6.95 W, corresponding to a peak power of 4.4 kW. The output of the all-fiber MOPA is launched into a 20 mm-long LBO crystal and a maximum secondharmonic power of 2.1 W is obtained at a fundamental power of 6.95 W with the optical conversion efficiency of 30.2%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 302006 (2015)
Materials and Thin Films
Effect of Gd on Microstructure and Properties of Laser Clad Magnesium Coatings
Chen Hong, Li Zhuguo, Yao Chengwu, and Wu Yixiong
The mechanical properties of ZM5 magnesium laser clad coatings are weaken by the lamellar β -Mg17Al12 phases on grain boundaries. The Mg-Al-Gd coatings on cast magnesium alloy are fabricated by laser cladding. The effects of Gd addition on the microstructures and tensile behaviors of coatings have been investigated. ThThe mechanical properties of ZM5 magnesium laser clad coatings are weaken by the lamellar β -Mg17Al12 phases on grain boundaries. The Mg-Al-Gd coatings on cast magnesium alloy are fabricated by laser cladding. The effects of Gd addition on the microstructures and tensile behaviors of coatings have been investigated. The results indicate that the Gd addition led to the formation of a cubic Al2Gd phase as well as suppresses the precipitation of the eutectic Mg17Al12 phase. The laser clad coating with 5.0% mass fraction Gd presents higher ultimate tensile strength and yield strength than that without Gd element at both room temperature and high temperature. The enhancement of heat resistant capacities is chiefly attributed to the existence of thermally stable Al2Gd particles, which prevents tiny liquation of eutectic phases along the grain boundaries and makes great contributions on maintaining high yield ratio during high-temperature deformation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306002 (2015)
Self-Organizing Nano-Structure and Optical Properties of Sapphire Induced by Low Energy Ion Beam
Chen Zhili, Liu Weiguo, and Yang Lihong
Electron cyclotron resonance (ECR) ion source is employed to erode the surface of sapphire (crystal orientation C) and the eroding effects and optical properties beams are researched at different low energy Ar + ion-beam incident angles. The experimental results indicate that, with ion beam energy 1200 eV, and beam curElectron cyclotron resonance (ECR) ion source is employed to erode the surface of sapphire (crystal orientation C) and the eroding effects and optical properties beams are researched at different low energy Ar + ion-beam incident angles. The experimental results indicate that, with ion beam energy 1200 eV, and beam current density 265 μA/cm2 , the increase of incident angle (5° ~40° ) obtains dot patterns on the sample surfaces; when the incident angle continues to increase up to 45°, orderly ripple structures appear on sample surfaces; the increase of incident angle (45°~70°) achieves column structures on sample surfaces in the direction of incident angle and orderly ripple structures in the direction perpendicular to incident angle; with the increase of incident angle, ripple wavelength on the sample surface firstly decreases slightly (45°~60°) and then gradually enlarges (60° ~70° ); when the incident angle is within 70° ~75° , dot patterns with larger aspect ratio emerge on sample surfaces. Eroding time extension is unable to change nano-struture topographies, but able to increase the vertical nano-structure dimensions and enhance the orderliness. In addition, enhancement of surface orderliness and height of nano-structures results in the increase of transmittance, which accounts for sample surface antireflections. The transformation of self-organized nano-structure patterns result from the interaction of spurting roughness and relaxation mechanism..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306003 (2015)
Influence of Tangential Airflows Velocity on Ablation Heat of Laser Irradiated Glass Fiber Reinforced Resin Composites
Zhang Jianmin, Ma Zhiliang, Feng Guobin, He Minbo, Liu Weiping, and Wei Chenghua
Ablation heat can be not only used to represent the capability in laser-hardening of composite, but also to describe the laser processing efficiency. Experiments are conducted to analyze the influence law of tangential airflows velocity at low subsonic and laser intensity on laser ablation heat of glass fiber reinforceAblation heat can be not only used to represent the capability in laser-hardening of composite, but also to describe the laser processing efficiency. Experiments are conducted to analyze the influence law of tangential airflows velocity at low subsonic and laser intensity on laser ablation heat of glass fiber reinforced epoxy resin composites. It shows that laser ablation heat decreases rapidly with the incident laser intensity firstly and then become stable at the same airflow velocity, when the laser irradiance is in the range of 100~500 W/cm2. The pivotal point of the ablation heat is about 200 W/cm2. On the condition that the laser intensity is below about 200 W/cm2, laser ablation increases with the airflow velocity with the same laser irradiation. On the contrary, laser ablation decreases with the airflow velocity. Ablation mechanism analysis indicates that the variation of utilizing efficiency of incident laser energy is attribute to the competition of multiple factors which include thermal diffusivity in material, surface combustion of pyrolysis gas, oxidative ablation of pyrolytic charcoal, radiation induced energy loss, and airflow denudation effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306004 (2015)
Microstructure and Deposition Mechanism of Ni60 Coatings Prepared by Supersonic Laser Deposition
Yang Lijing, Li Zhihong, Li Bo, Zhang Qunli, and Yao Jianhua
As a new composite spraying technology combining the advantages of laser and cold spray, supersonic laser deposition (SLD) is able to deposit materials which are difficult or impossible to deposit by cold spray technique alone. Ni60 coatings are successfully fabricated on the surface of medium carbon steel by SLD. The As a new composite spraying technology combining the advantages of laser and cold spray, supersonic laser deposition (SLD) is able to deposit materials which are difficult or impossible to deposit by cold spray technique alone. Ni60 coatings are successfully fabricated on the surface of medium carbon steel by SLD. The deposition efficiency, bonding mechanism, microstructure, composition and micro-hardness are characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and microhardness tester, respectively. The results show that the thickness of deposited layer significantly increases with the rising of deposition temperature, the spherical indentation on surface decreases. Compared with Ni60 particles, the Ni60 deposited coating preserves the status of solid-state deposition, and has the same microstructure and phase with powder. The bonding mechanism is mainly mechanical interlocking and metallurgical bonding under laser irradiation. Average micro-hardness of the deposited coating is 867 Hv0.3, which is 8%~10% higher than that of the original powder due to cold hardening..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306005 (2015)
Influence of Ni Additions on the Microstructures and Properties of Laser Clad CuAl10 Coatings
Yang Jiaoxi, Wen Qiang, Li Ziyang, and Xiao Zhiyong
To further improve the corrosion resistance performance of CuAl10 alloy laser cladding coating, the influence of Ni additions on the microstructures and properties of CuAl10 coatings produced by laser cladding is investigated. Laser cladding is performed on 316L stainless steel surface by a HPDL-D30 diode laser with diTo further improve the corrosion resistance performance of CuAl10 alloy laser cladding coating, the influence of Ni additions on the microstructures and properties of CuAl10 coatings produced by laser cladding is investigated. Laser cladding is performed on 316L stainless steel surface by a HPDL-D30 diode laser with direct injection powders. Laser cladding coatings are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and microhardness tester. The electrochemical corrosion behavior of cladding layers is evaluated. The results show that the coating have an excellent metallurgical bonding with the substrate and homogeneous microstructure. The addition of Ni element can significantly improve the corrosion resistance performance of laser cladding coatings. The corrosion resistance of claddings increase with increasing the mass fraction of Ni, reaching a maximum at 6.0%. The cladding without Ni mainly consists of α - Cu, α - Fe, AlFe3 and Cu9Al4, while the addition of Ni element cladding mainly consists of α - Cu, α - (Cu,Ni), AlCu3 and Cu9Al4..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 306006 (2015)
Measurement and Metrology
Analysis of Absorption and Scattering Properties of Water Host Haze Droplet with Insoluble Solid Inclusion
[in Chinese], [in Chinese], [in Chinese], and Gerard Grehan
The effect of a insoluble solid inclusion on optical property of a haze droplet is investigated. The efficiencies such as scattering, absorption, and extinction of a haze droplet with five nuclei including cellulose, quartz, polystyrene, hematite, and soot are calculated by using a core- shell model, respectively. BesiThe effect of a insoluble solid inclusion on optical property of a haze droplet is investigated. The efficiencies such as scattering, absorption, and extinction of a haze droplet with five nuclei including cellulose, quartz, polystyrene, hematite, and soot are calculated by using a core- shell model, respectively. Besides the haze size, the parameters including size of non- absorbent nucleus, weak- absorbent one, strong- absorbent core are discussed. The results showed that scattering of a PM2.5 haze droplet with a non-absorbent nucleus is stronger than that with an absorbent one. The scattering of a PM2.5 haze droplet is nonlinearly dependent on its size parameter y, the nucleus size x, and the complex refractive index m1. Absorption of the droplet is determined by its relative diameter β and m1. The above results may give guidance for further study on accurate assessment of haze visibility and laser diagnostics of multiphase flow complex medium in high humidity environment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308001 (2015)
An Automatic Registration Algorithm for Point Cloud Based on Feature Extraction
Huang Yuan, Da Feipeng, and Tao Haiji
A automatic registration algorithm for point cloud based on feature extraction is presented for threedimensional point cloud data obtained under different views. The algorithm extracts the feature points according to the variation of normal vector within various radius, and finds matching point pairs by using three geoA automatic registration algorithm for point cloud based on feature extraction is presented for threedimensional point cloud data obtained under different views. The algorithm extracts the feature points according to the variation of normal vector within various radius, and finds matching point pairs by using three geometric features of local point clouds comprehensively. The accurate matching point pairs by using distance restriction are obtained and the initial registration parameters are calculated. During the phase of accurate registration, the improved iterative closest point (ICP) should be used to finish the second mosaicking. The experimental results show that the proposed algorithm is more effective than traditional ICP in terms of run time and accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308002 (2015)
Focused Laser Self-Mixing Interference Caused by Rotatable Reflector
Guo Yang, and Zhong Jingang
Rotation of a reflector leads to a phenomenon of self-mixing interference (SMI) of a beam of unfocused laser. There are methods proposed for a measurement of angle by using the unfocused-laser SMI. However, the range of angle measurement is limited by the size of the utilized laser aperture. The SMI of the beam of focuRotation of a reflector leads to a phenomenon of self-mixing interference (SMI) of a beam of unfocused laser. There are methods proposed for a measurement of angle by using the unfocused-laser SMI. However, the range of angle measurement is limited by the size of the utilized laser aperture. The SMI of the beam of focused laser is studied. A new approach to measure an angle by use of focus-laser SMI is proposed. The approach is able to achieve an angle measurement with an order of magnitude higher than the existent methods do. The increase of range in angle measurement by the proposed approach is achieved by placing a focusing lens into the optical path. The lens are used to collect the light, which deviates from emergent one, back into the resonator of laser. The SMI occurrs as a consequence of the collected light. The proposed approach is experimentally validated. The experiments also show that the increase in the focal length of the utilized lens can enlarge the range of angle measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308003 (2015)
A One-Dimensional Phase-Shift Technique Based on Dual-Frequency Crossed Fringe for Phase Measuring Deflectometry
[in Chinese], Evelyn Olesch, [in Chinese], and Gerd Hausler
Phase measuring deflectometry (PMD) needs the two components of the local surface gradient via a sequence of two orthogonal sinusoidal fringe patterns that have to be displayed and captured separately. A novel phase-shift technique by using the cross fringe pattern is introduced, in which a one-dimensional N-phase shifPhase measuring deflectometry (PMD) needs the two components of the local surface gradient via a sequence of two orthogonal sinusoidal fringe patterns that have to be displayed and captured separately. A novel phase-shift technique by using the cross fringe pattern is introduced, in which a one-dimensional N-phase shift allows for the acquisition of the two orthogonal phases, with only N exposures instead of 2N exposures. Therefore, it makes PMD possible be implemented by a one- dimensional translation of the fringe pattern, instead of the common two-dimensional translation, which will be quite useful for certain applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308005 (2015)
Centerline Extraction of Structured Light Stripe Based on Principal Component Analysis
Cai Huaiyu, Feng Zhaodong, and Huang Zhanhua
Centerline extraction of structured light stripe is the key step of topography measurement. The centerline extraction of structured light stripe based on the principal component analysis is proposed. Otsu′ s method is used to extract the region of interest (ROI) area of image. After twice Gaussian convolution, the gradCenterline extraction of structured light stripe is the key step of topography measurement. The centerline extraction of structured light stripe based on the principal component analysis is proposed. Otsu′ s method is used to extract the region of interest (ROI) area of image. After twice Gaussian convolution, the gradient distribution of the ROI area is got, then the rough position of the stripe center is obtained based on the gradient distribution. Using principal component analysis the normal vector is obtained. Based on the rough position of the stripe center, the center of structured light stripe can be found in normal directions with second order Taylor series expansion of grayscale distribution function. The experimental results show that the algorithm has higher speed and precision characteristics. Compared with Steger algorithm, the mean square error (MSE) is less than 0.003 pixel, and it is nearly three times as fast as Steger algorithm. This method can realize the rapid and high precision extraction of structured light stripe, and lays a foundation of real-time application for structure light vision detecting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308006 (2015)
Blind Image Deconvolution Based on Power Law Distribution Applied in Optoelectronic Detection System
Cao Lei, Chen Hongbin, Qiu Qi, Ren Ge, Xu Zhiyong, Zhang Jianlin, and Qi Bo
Because of the impacts of atmospheric turbulence, only blurred degraded image is obtained with optical detection system. A novel fast blind image deconvolution algorithm is proposed based on the specialty that most images spectral amplitude is of power law distribution, and the original estimate of the degrading procesBecause of the impacts of atmospheric turbulence, only blurred degraded image is obtained with optical detection system. A novel fast blind image deconvolution algorithm is proposed based on the specialty that most images spectral amplitude is of power law distribution, and the original estimate of the degrading process directly from degraded image can largely accelerate the speed of algorithm convergence and improve the stablity. Based on the estimation, the fine estimate of point spread function is carried on, which iteratively combined with Wiener filter image deconvolution, it ensures that the algorithm is of accurate deconvolution and universality, and finally deconvolute the image fast and effective. Experimental results show that a photoelectric detection system based on power law incremental Wiener filter (BPL- IWF) blind deconvolution of images can detect targets real time and output BPL-IWF blind deconvolution image in quasi-real time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308007 (2015)
Study on Ronchi Shearing Interferometry for Wave-Front Aberration Measurement of Lithography Projection Lens
Wu Feibin, Tang Feng, Wang Xiangzhao, Li Jie, and Li Sikun
Ronchi shearing interferometry modulates the spatial coherence of light field with extended source. With the advantages of simple structure, common- path, null- fringe detection, and so on the Ronchi shearing interferometer can be used for in situ aberration measurement of lithography projection lens. Ronchi shearing iRonchi shearing interferometry modulates the spatial coherence of light field with extended source. With the advantages of simple structure, common- path, null- fringe detection, and so on the Ronchi shearing interferometer can be used for in situ aberration measurement of lithography projection lens. Ronchi shearing interferometry for wave-front aberration measurement of lithography projection lens is studied. The interference model of Ronchi shearing interferometer is derived by theories of grating diffraction and spatial coherence. A tenstep phase-shifting algorithm is proposed to eliminate negative effects of unwanted interference from the high order diffraction light, which limits the accuracy of phase retrieval. The effects of the first ±9 orders interference on phase retrieval accuracy can be eliminated. The peak-valley (PV) value and root mean square (RMS) value of theoretical phase retrieval error are less than 0.0046 λ and 0.0019 λ respectively. The theoretical interference model and the phase retrieval algorithm are validated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 308008 (2015)
Optical Communication
Research on the Signal Processing in Optical Fiber Coherent Optical Time Domain Reflectometer Based on Grey Scale Image
Zhao Shiqi, Pang Fufei, He Mengting, Xu Hui, and Wang Tingyun
The technique of combining histogram equalization and gradient method was proposed for the processing of optical fiber sensor signal in a coherent optical time domain reflectometer (COTDR). Treating the signals detected by the same optical pulse sent into the sensor fiber as a row vector, and the signals of the same poThe technique of combining histogram equalization and gradient method was proposed for the processing of optical fiber sensor signal in a coherent optical time domain reflectometer (COTDR). Treating the signals detected by the same optical pulse sent into the sensor fiber as a row vector, and the signals of the same position detected by a set of optical pulses as a column vector, a two- dimensional grey scale image is built. Through calculating the gradient of the grey scale image, and then histogram equalization, the noise resulted from the environmental interference is depressed. The resolution is improved. With the proposed method, the vibration signal driven by a piezoelectric ceramic transducer in the COTDR with a 2.5 km length sensing optical fiber is identified well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305001 (2015)
Integral Method of Stress Birefringence Calculation and Fiber Design Optimization
Yu Pan, and Ji Minning
The calculation method of stress field and birefringence at the fiber core center with any stress region shape is studied. The design of bow- tie fiber is optimized. With the help of solid mechanics module in COMSOL Multiphysics software, stress field distribution at fiber core center is studied when the stressinduced The calculation method of stress field and birefringence at the fiber core center with any stress region shape is studied. The design of bow- tie fiber is optimized. With the help of solid mechanics module in COMSOL Multiphysics software, stress field distribution at fiber core center is studied when the stressinduced fiber has same stress area and different stress region shapes. The result shows that the numerical value acquired by integral method agrees with the value from software simulation. Therefore, the stress distribution and birefringence at fiber core center can be calculated by integral method directly even if the stress- induced fiber has any stress region shape. By means of stress element analysis based on integral method, it is found that the bow- tie fiber birefringence at fiber core is not the biggest compared with other type of stress- induced fiber if their stress area is the same. This is against the usual conclusion that the birefringence of bow- tie fiber is maximal. To get higher birefringence, bow- tie fiber is optimized again. As a result, a new fiber with“lunar”stress region is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305002 (2015)
Analysis and Experiments of the Arc Heating for Fiber Fused Biconical Taper Technology
Zhang Wei, Rong Weibin, Yang Wei, Wang Lefeng, and Sun Lining
The heating temperature is one of the key factors in the fiber fused biconical taper manufacture, which can affect the component performance. In order to improve the temperature stability and controllability in the heating region, the high- voltage arc heating device is presented and arc heating, heating region temperaThe heating temperature is one of the key factors in the fiber fused biconical taper manufacture, which can affect the component performance. In order to improve the temperature stability and controllability in the heating region, the high- voltage arc heating device is presented and arc heating, heating region temperature and fiber preheating are studied. The high- frequency high voltage power source, in which the current and frequency can be adjusted independently, and electrodes are designed. The closed- loop controls of the voltage and current are applied to ensure the success of the arc ignition and the stability of the arc discharge current, and the discharge process is analyzed. The temperature detection device in which the infrared camera is adopted to measure the heating region temperature by the ceramic rod is designed. Through the analysis of experimental data, the relationships among the frequency, arc control voltage, arc current, heating distance and arc region temperature are determined. According to experiments and computation results, the temperature of the arc center region can reach 1635 ℃ within the stability of 2.37 ℃ . Based on the established heating model for fine fibers with the diameter of 80 μm , the preheating time is computed by the transient analysis of the ANSYS software. It is shown that the temperature of the heating region can reach the stability by 25 s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305003 (2015)
A Three-Dimentional Vector Hydrophone Based on Fiber-Optic Flexural Disk Accelerometer
Jin Mengqun, Zhang Zili, Wu Guojun, and Ge Huiliang
Fiber-optic vector hydrophone (FOVH), with many advantages including high sensitivity, large dynamic range, intrinsic immunity to electromagnetic interference and light weight, is becoming a hotspot of new-style vector sensors. For array applications, finite element methods and experimental results of the fiberoptical Fiber-optic vector hydrophone (FOVH), with many advantages including high sensitivity, large dynamic range, intrinsic immunity to electromagnetic interference and light weight, is becoming a hotspot of new-style vector sensors. For array applications, finite element methods and experimental results of the fiberoptical flexural disk vector hydrophone are discussed (FOVH). Two finite element analysis methods are presented to forecast the performance, fiber-layer equivalent method (FLEM) and fiber-layer division method (FLDM), then a fiber-optic flexural disk vector hydrophone is developed and related metrology aspects of measurement is demonstrated. The experimental results are presented that pressure phase sensitivity of the hydrophone is -182 dB@100 Hz~-158.5 dB@1000 Hz (ref.1 rad/μPa ) at the range from 100 Hz to 1000 Hz. The cross-sensitivity is less than -30 dB. It possesses a good directional performance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305004 (2015)
Research on Inhibiting Radial Magnetic Sensitivity of Fiber-Optic Gyroscope
Liu Jun, Xiao Cheng, Pan Xin, Yin Jianling, and Lu Jun
The magnetic sensitivity of fiber-optic gyroscope (FOG) in radial magnetic field, which is parallel to optical fiber coil plane, is studied. The optical fiber twist, which is the main mechanism of the radial magnetic sensitivity, is analysed. Based on this mechanism, the use of compensation fiber ring to inhibit FOG raThe magnetic sensitivity of fiber-optic gyroscope (FOG) in radial magnetic field, which is parallel to optical fiber coil plane, is studied. The optical fiber twist, which is the main mechanism of the radial magnetic sensitivity, is analysed. Based on this mechanism, the use of compensation fiber ring to inhibit FOG radial magnetic sensitivity is proposed. By controlling the twist characteristics of the compensation optical fiber, a controllable phase is introduced to offset the radial magnetic sensitivity error of the original optical fiber ring. The model of the relationship between the compensation phase, radial magnetic sensitivity axis associated and the twist characteristics of optical fiber is established. The data simulation and experiment are carried out. By defining the compensation efficiency, inhibition effect of the radial magnetic sensitivity is evaluated. In experimental results, radial magnetic sensitivity compensation efficiency is 63.76%, and the synthesized magnetic sensitivity compensation efficiency is 42.83%. To a certain extent, this method can inhibit the radial magnetic sensitivity of FOG..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305005 (2015)
Gamma Sensing Characterization of Cerium-Doped Silica Scintillating Fiber
Lin Shiyang, Guo Qiang, Pang Fufei, Chen Zhenyi, and Wang Tingyun
Scintillating silica optical fibers are fabricated by using Sol- Gel method. Based on the fabricated scintillating fibers, a Gamma radiation fiber sensor system is set up. Through doping different concentrations of cerium (Ce) element in Sol-Gel material, two scintillating fibers are fabricated with the Ce and Si mole Scintillating silica optical fibers are fabricated by using Sol- Gel method. Based on the fabricated scintillating fibers, a Gamma radiation fiber sensor system is set up. Through doping different concentrations of cerium (Ce) element in Sol-Gel material, two scintillating fibers are fabricated with the Ce and Si mole fraction of 0.14% and 0.22%. By using a 137Cs Gamma radiation source, the dependences of the sensing properties on the fiber coating, Ce-doped concentration and fiber length are investigated and analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305006 (2015)
Optical Model Non-Reciprocity of Microsphere Resonator Excited by Tapered Fiber for Resonator Optic Gyroscope
Wang Minghuan, Tang Jun, Guo Zebin, Shang Chenglong, Zhang Tian′en, Lei Longhai, Guo Hao, Liu Jianhua, Xue Chenyang, Zhang Wendong, and Liu Jun
Based on Rsoft software, the tapered fiber evanescent field distribution is simulated, and the reason for the nonreciprocity of micro- resonator excited by tapered fiber is analyzed in theory. Optical fiber fused silica microsphere cavity is used in the experiment. Through high precision three dimensional adjustment alBased on Rsoft software, the tapered fiber evanescent field distribution is simulated, and the reason for the nonreciprocity of micro- resonator excited by tapered fiber is analyzed in theory. Optical fiber fused silica microsphere cavity is used in the experiment. Through high precision three dimensional adjustment along the fiber direction, test points are selected after moving the same distance and microsphere cavity resonance spectra are recorded under the case of forward and converse transmission of light, getting the regular pattern of non-reciprocity of the resonance spectral parameters with the variation of evanescent field. By calculating the frequency discrimination curve of microsphere cavity, the influence of non- reciprocity on the dynamic range and sensitivity of gyroscope is got, and suppression methods are proposed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 305007 (2015)
Optical Design and Fabrication
Design and Analysis of the Polarization-Preserving Films for Rectangular Prism
Li Zhaohui, Wang Zhao, Huang Junhui, Qi Jingya, Yu Bao, and Guo Junjie
An extra constant difference between s and p component is produced after the light gets through the reflector based on total reflection,which lead to the change of the polarization state as a result. A novel design method of the polarization-preserving films for rectangular prism based on high-reflection films is propoAn extra constant difference between s and p component is produced after the light gets through the reflector based on total reflection,which lead to the change of the polarization state as a result. A novel design method of the polarization-preserving films for rectangular prism based on high-reflection films is proposed after deep analysis on its working mechanism and the geometry of the prism.The polarization state is kept invariant by plating the designed films on the two planes of the prism.The method has been theoretically and experimentally proved to be feasible.It is also easy to realize commercial application with the mature fabrication process of the high-reflection films. What′s more,the polarization-preserving characteristic of the method works well with little incidence error..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 316002 (2015)
Remote Sensing and Sensors
Compensation for Star Centroid Systematic Error of Star Trackers
Jiang Liang, Zhang Liguo, Zhang Xingxiang, and Ren Jianyue
The frequency of star centroid systematic error is analized, the common quality of star centroid systematic error distributions with different point spread functions is found. A simulation using Monte Carlo method is done according to the point spread function data of different field of views (FOV) from optical system.The frequency of star centroid systematic error is analized, the common quality of star centroid systematic error distributions with different point spread functions is found. A simulation using Monte Carlo method is done according to the point spread function data of different field of views (FOV) from optical system. The result of simulation is in accordance with frequency analysis. The star centroid systematic error of the star object whose dispersion spot dimensions are 5 pixel × 5pixel is experimentally measured. The star centroid systematic error is compensated with error compensation equations, after compensation the accuracy of central FOV is increased by 66.56% , and the accuracy of fringe FOV is increased by 57.21% . So the effect of the compensation using the proposed method is better than the traditional compensation method using sine curve fitting with the accuracy only increased by 35.7%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 314001 (2015)
TLS Laser Intensity Correction Based on Polynomial Model
Tan Kai, and Cheng Xiaojun
Starting from the laser radar range equation, the polynomial model is adopted to fit the relationship between the laser intensity value and the received power based on the instrumental radiometric mechanism. Because of the unknown system parameters and target reflectance, it is impossible to compute the definite receivStarting from the laser radar range equation, the polynomial model is adopted to fit the relationship between the laser intensity value and the received power based on the instrumental radiometric mechanism. Because of the unknown system parameters and target reflectance, it is impossible to compute the definite received laser power. So, by constructing the new variable constituted by the combination of the cosine of the incidence angle and the square of the range, the scanning geometry factors and target reflectance are separated and the polynomial model is used to fit the relationship between the laser intensity and the new variable. The standard range and the standard incidence angle are defined, and the intensity biases caused by the range and the incidence angle are corrected by analyzing. Experiments are conducted to test and verify the proposed method. Results show that the method can effectively remove the variations and biases caused by the range and incidence angle as well as accurately obtain the corrected laser intensity value proportional to the reflectance of the scanned point..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 314002 (2015)
Spectroscopy
Method of Power Spectrum Estimation Based on LMD-Teager Transformation
Cai Jianhua, and Wang Xianchun
Local mean decomposition (LMD) method is a new adaptive signal processing method. Teager energy operator is an algorithm to solve the signl instantaneous energy, which can effectively extract instantaneous energy of nonlinear signals. Combined with the advantages of two methods, a method of power spectrum estimation isLocal mean decomposition (LMD) method is a new adaptive signal processing method. Teager energy operator is an algorithm to solve the signl instantaneous energy, which can effectively extract instantaneous energy of nonlinear signals. Combined with the advantages of two methods, a method of power spectrum estimation is proposed based on LMD- Teager transformation. The principle and steps of the method are presented and the physical meaning of power spectrum estimation is discussed. On the basis of the comparison with the fast Fourier tranform algorithm (FFT) method and wavelet transform, A short data sequence and non-stationary signal are simulated to verify the effect of the proposed method. The results show that the proposed method breaks through the difficulty that the FFT method just can process the stationary signal, and it is more suitable for non-stationary signal. The length of the required data is shorter than that in Fourier method, and the analysis accuracy and resolution are better than that of traditional Fourier method and wavelet transform..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 315001 (2015)
Detection of Trace Impurities in Uranium Using Laser Induced Breakdown Spectroscopy
Xu Qinying, Zhang Yongbin, Wang Huaisheng, and Jia Jianping
Feasibility of rapid quantitative analysis for trace impurities in uranium materials is studied using laser induced breakdown spectroscopy (LIBS). LIBS system is set up with a KrF excimer laser and an AvaSpec-2048 fiber optic spectrometer. Spectral data both of uranium and impurity elements are detected and analyzed inFeasibility of rapid quantitative analysis for trace impurities in uranium materials is studied using laser induced breakdown spectroscopy (LIBS). LIBS system is set up with a KrF excimer laser and an AvaSpec-2048 fiber optic spectrometer. Spectral data both of uranium and impurity elements are detected and analyzed in a range of 200~460 nm wavelength. The influence of pulse number and delay time of spectrometer detection on the characteristics of uranium and impurity elements is investigated respectively. Three kinds of impurity elements Fe, Cu and Al in uranium are quantitatively analyzed with characteristic spectra at 438.3, 427.5, 396.2 nm respectively. The relative error of quantitative measurement is less than 12% when the laser energy is 28 mJ and time delay is 1.5 μs . The experimental results show that laser induced breakdown spectroscopy which has relatively lower relative error and limit of detection can be used for rapid quantitative analysis of trace impurity elements in uranium materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 315002 (2015)
Raman Spectral Profiles of PHB Synthesis by Cupriavidus necator H16 at Different Fructose Levels
Qin Zhaojun, Peng Lixin, Zhu Libo, Song Shuishan, Liu Junxian, and Wang Guiwen
Laser tweezers Raman spectroscopy technology is used to explore the accumulation of biodegradable plastic poly-β -hydroxybutyric acid (PHB) in Cupriavidus necator H16 at single- cell level. With ammonium sulfate (2 g/L) as nitrogen source, the fermentation of PHB is performed with 0%, 0.5%, 1.0%, 2.0% or 3.0% of fructoLaser tweezers Raman spectroscopy technology is used to explore the accumulation of biodegradable plastic poly-β -hydroxybutyric acid (PHB) in Cupriavidus necator H16 at single- cell level. With ammonium sulfate (2 g/L) as nitrogen source, the fermentation of PHB is performed with 0%, 0.5%, 1.0%, 2.0% or 3.0% of fructose (mass fraction) and Raman spectra of single cell are acquired at different time of incubation respectively. Major results are as follows. 1) The fermentation performs ideal PHB product yield at 20 g/L of fructose. 2) At different fructose levels, C. necator H16 cells take almost the same steps to synthesize bio-macromolecule in the initial and early stages of fermentation, while higher fructose level extends the log phase of growth. 3) The dynamics of Raman intensity from peaks 782, 1574, 1656 and 1732 cm–1, which derive from RNA, DNA, proteins and PHB respectively, reveals that the cells show stronger Raman intensity of nucleic acid for longer time under higher level of fructose, and this may be of important factor affecting the accumulation of PHB. 4) The average intensity of single cell at peak 1732 cm- 1 shows linear relationship with yield of PHB and can quantitatively follow the PHB production. This observation uncovers the kinetics of major bio-macromolecule of C. necator H16 during the PHB accumulation at different fructose levels, provides novel spectral information for the PHB fermentation. This work shows the potential of laser tweezers Raman spectroscopy for the quick screening of high-yield PHB strains..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 3, 315003 (2015)
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