Journals >Chinese Journal of Lasers
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2013
Volume: 40 Issue 5
42 Article(s)
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[in Chinese]
Frequency Noise Suppression of a Dye Laser Based on Intracavity Electro-Optic Modulator
Liu Fang, Wang Chun, Li Liufeng, and Chen Lisheng
The frequency noise of a continuous-wave tunable dye laser is suppressed by using the Pound-Drever-Hall frequency locking method. To cope with relatively large high-frequency components in the dye laser frequency noise, a compact intracavity electro-optic modulator that serves as a fast frequency actuator is designed aThe frequency noise of a continuous-wave tunable dye laser is suppressed by using the Pound-Drever-Hall frequency locking method. To cope with relatively large high-frequency components in the dye laser frequency noise, a compact intracavity electro-optic modulator that serves as a fast frequency actuator is designed and assembled. The design parameters of the modulator are discussed in detail and the experimental data on the mechanical resonances of two commonly used electro-optic crystals are given. The dye laser is locked to a Fabry-Perot cavity by using the intracavity electro-optic modulator and piezoelectric transducers installed on the cavity mirrors. With only piezoelectric actuators the laser frequency noise is reduced by three orders of magnitude at 100 Hz and the noise is further suppressed by four-fifths from 100 Hz to 50 kHz with a combination of piezoelectric actuators and the intracavity electro-optic modulator. With the suppression of frequency noise implemented, the 2.2 MHz free-running laser linewidth is reduced to 10 kHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 517001 (2013)
Research Article
Modeling of Atmospheric Polarization Pattern Based on Vector Radiative Transfer
Wang Wei, Chu Jinkui, Cui Yan, Zhi Wei, and Chen Chen
Atmospheric radiative transfer is investigated to obtain the actual skylight polarization pattern. The simplified double-layer atmospheric model is used to simulate actual atmosphere. The vector radiative transfer equation (VRTE) is solved by means of polarized radiative transfer based on the adding-doubling method (RTAtmospheric radiative transfer is investigated to obtain the actual skylight polarization pattern. The simplified double-layer atmospheric model is used to simulate actual atmosphere. The vector radiative transfer equation (VRTE) is solved by means of polarized radiative transfer based on the adding-doubling method (RT3) to get the Stokes parameters of light wave in the discrete points of the sky. Then the skylight polarization information is calculated according to the solution of VRTE. The skylight polarization pattern based on RT3 is built and compared with Rayleigh scattering theory model. The results show that, at the weather conditions of clear sky, cloudy sky and thick cloudy, the degree of polarization (DOP) is gradually reduced, especially for the long wavelength. Simulation results are in good agreement with the traditional Rayleigh scattering theory model. It can also reveal the impact of different weathers, different wavelengths and different albedos on skylight polarization. Therefore it is conducive for the measurement and application of polarized light in actual atmosphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 513001 (2013)
Retrieval and Analysis of Aerosol Lidar Ratio at Several Typical Regions in China
Zhang Zhaoyang, Su Lin, and Chen Liangfu
In order to solve the problem that most of micro-pulse lidars cannot obtain lidar ratio (LR) independently, LR from aerosol size distribution and complex refractive index is acquired with Mie scattering theory. Four aerosol robotic network (AERONET) stations that include SACOL station, Beijing station, Shouxian stationIn order to solve the problem that most of micro-pulse lidars cannot obtain lidar ratio (LR) independently, LR from aerosol size distribution and complex refractive index is acquired with Mie scattering theory. Four aerosol robotic network (AERONET) stations that include SACOL station, Beijing station, Shouxian station and Taihu station are used. The LR variation characteristics of seasonal-mean and years′ average values in different regions and aerosol types are analyzed by using LR and Angstrom wavelength index. The conclusions are as follows: LRs in chinese different regions and seasons show complex and different variation characteristics; the LR in Yulin is the least and years′ average value is (36.3±15)sr; LRs are relatively larger in Taihu, Beijing and Shouxian; annual average value of 2008 is smaller than other years in Beijing and there is little variation of years′ average value in other regions. LR and Angstrom wavelength index can distinguish aerosol type and they both increase from north to south in the analysis regions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 513002 (2013)
Biomedical Photonics and Laser Medicine
Toxicity of Quantum Dots on Mouse Ovarian Granulosa Cells
Xie Xiangyi, Zhu Xiaomei, Teng Huan, Zhai Peng, Wang Guangsun, Lin Suxia, Wang Xiaomei, Xu Gaixia, and Niu Hanben
This study investigates the toxicity of CdTe quantum dots (QDs) on mouse ovarian granulosa cells in vitro. The fluorescence stabilities of QDs in DMEM culture medium, M1640 culture medium and phosphate buffer solution (PBS) are measured by fluorometer, respectively. Apoptosis is observed by chromatin staining with HoecThis study investigates the toxicity of CdTe quantum dots (QDs) on mouse ovarian granulosa cells in vitro. The fluorescence stabilities of QDs in DMEM culture medium, M1640 culture medium and phosphate buffer solution (PBS) are measured by fluorometer, respectively. Apoptosis is observed by chromatin staining with Hoechst32258 and cell viability is detected by cell counting kit-8 (CCK-8) assay after the granulosa cells are treated with QDs. The results demonstrate that the fluorescence stability of QDs in DMEM culture medium is better than that in the other media, the QDs fluorescence emission spectrum in it does not shift and the intensity decreases only 9.8%. It is found that the apoptosis of granulosa cells treated with QDs is dosage-dependent by the Hochest32258 staining, which is confirmed by the CCK-8 assay. The research demonstrates that the QDs at lower concentration have not affected the morphology and function of granulosa cells in vitro. However, with the increase of accumulation of QDs inside cytoplasm, the apoptosis increases significantly. This study offers very useful information of reproductive toxicity of QDs to guide the safe application of QDs in vivo..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 504001 (2013)
A Methodology on Time-Domain Fluorescence Diffuse Optical Tomography Based on GPU-Accelerated Monte-Carlo Modeling
Yi Xi, Wu Linhui, Wang Xin, Chen Weiting, Zhang Limin, Zhao Huijuan, and Gao Feng
A graphics processing unit (GPU) accelerated Monte Carlo (MC) approach is developed for modeling photon migration in an arbitrarily complex turbid medium, where the diffusion equation (DE) might behave an ineffective modeling tool. Then an image reconstruction algorithm of time-domain fluorescence diffuse optical tomogA graphics processing unit (GPU) accelerated Monte Carlo (MC) approach is developed for modeling photon migration in an arbitrarily complex turbid medium, where the diffusion equation (DE) might behave an ineffective modeling tool. Then an image reconstruction algorithm of time-domain fluorescence diffuse optical tomography is proposed based on the developed GPU-accelerated MC calculations, within the framework of the generalized pulse spectrum technique. Simulated results show that the MC-based approach retrieves on the position and shape of the targets in complexly structured domain that include low absorbing and high scattering, low absorbing and low scattering, high absorbing and low scattering, high absorbing and high scattering, and/or void regions, with higher accuracy than the DE-based one, demonstrating the improved generality of the proposed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 504002 (2013)
Killing Effect of Photodynamic Therapy Induced by PsD007 on Human Epidermoid Carcinoma in Vitro
Chen Hongli, Yin Huijuan, Xu Zengrui, Wang Minghui, Zheng Liqing, and Li Yingxin
We investigate the killing effect of photodynamic therapy (PDT) induced by photocarcinorin (PsD007) on human epidermoid carcinoma Hep-2 in vitro, and explore the preliminary killing mechanism. Methyl thiazolyl tetrazolium (MTT) colorimetric assay is applied to measure the relative survival rate of PDT with different phWe investigate the killing effect of photodynamic therapy (PDT) induced by photocarcinorin (PsD007) on human epidermoid carcinoma Hep-2 in vitro, and explore the preliminary killing mechanism. Methyl thiazolyl tetrazolium (MTT) colorimetric assay is applied to measure the relative survival rate of PDT with different photosensitizer concentrations, light doses and antioxidants. Confocal microscope is used to observe the subcellular localization of PsD007. Annexin V/PI double staining is used to detect the apoptosis rate. DCFH-DA probe is used the to detect reactive oxygen species (ROS) production. The fatality rate of PDT on Hep-2 can be as high as 85.4%, and is positively correlated with photosensitizer concentration and energy density. Three kinds of antioxidants can all antagonize the damage effect induced by PDT in different degree, while sodium azide has the best effect. The fluorescence images of PsD007 subcellular localization demonstrate that PsD007 diffuses into the mitochondria. Two hours after PDT, the ROS production is as 2.71 times as control group. The apoptosis rate is up to 49.5% (energy density is 1.2 J/cm2) and 70.2% (energy density is 4.8 J/cm2) four hours after PDT. PsD007-PDT could significantly kill Hep-2 cells and induce apoptosis that mitochondria may be the initial target..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 504003 (2013)
Laser Manufacturing
Effect of Welding Speed on Melt Flow Behavior in High Speed Laser Welding Process
Pei Yinglei, Shan Jiguo, and Ren Jialie
Typical welding defects of the high speed laser welding process have a close relationship with the melt flow of molten pool. The investigation of melt flow behavior can help to further understand the formation mechanism of defects in the high speed welding process. In this study, fiber laser is used to weld austenitic Typical welding defects of the high speed laser welding process have a close relationship with the melt flow of molten pool. The investigation of melt flow behavior can help to further understand the formation mechanism of defects in the high speed welding process. In this study, fiber laser is used to weld austenitic stainless steel sheet. The effect of welding speed on melt flow behavior has been investigated. The surface flow behavior is studied by high speed visual detection system. In addition, the inner flow is studied through Ti tracer method. The results show that with the welding speed increasing, the flow distance of surface flow from keyhole to rear goes up, the molten metal in the middle of molten pool moves to the bottom and rear of pool with a longer distance. The effect of the welding speed on melt flow near the edge of the molten pool is small. It can be accounted that, with the welding speed increasing, the angle between vapour plume and pool surface decreases, the horizontal component of the vapour force will improve, which causes the backward driving force to increase and the flow distance of the surface flow to increase..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503001 (2013)
Influence of Laser Shock Processing on Tensile Properties and Tribological Behaviors of AISI304 Stainless Steel
Zhong Jinshan, Lu Jinzhong, Luo Kaiyu, Qi Han, Wang Zhilong, Han Bin, and Liu Juan
Tensile properties and wear behaviors of AISI304 stainless steel after laser shock processing (LSP) with different processing parameters are investigated. Ultimate tensile strength (UTS) values and stress-strain curves of all four kinds of tensile samples are measured, and the improvement mechanism of UTS generated by Tensile properties and wear behaviors of AISI304 stainless steel after laser shock processing (LSP) with different processing parameters are investigated. Ultimate tensile strength (UTS) values and stress-strain curves of all four kinds of tensile samples are measured, and the improvement mechanism of UTS generated by LSP is also revealed. Wear properties and friction coefficients of AISI304 stainless steel with and without LSP are compared, and the influence rule of LSP on wear properties and friction coefficients of AISI304 stainless steel are systematically analyzed. The results show that LSP can improve the UTS of AISI304 stainless steel, which is due to the surface nanocystalization. In addition, LSP enhances the wear properties, and slightly increases the friction coefficients of AISI304 stainless steel..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503002 (2013)
Microstructure, Composition and Corrosion Resistance of Laser Cladding Fe-Based Coatings with High Hardness
Li Meiyan, Han Bin, Gao Ning, Wang Yong, and Pan Jiaoliang
SDFe55 alloy coating with high hardness (850 HV0.2) is prepared on the surface of piston by laser cladding. The structure, composition and corrosion resistance are studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro analysis (EPMA) and corrosion testing. The results shoSDFe55 alloy coating with high hardness (850 HV0.2) is prepared on the surface of piston by laser cladding. The structure, composition and corrosion resistance are studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro analysis (EPMA) and corrosion testing. The results show that laser cladding Fe-based coating is uniform without cracks and pores, has metallurgical bonding with the matrix, and is composed by γ(Fe, Ni) and carbides of type M23C6 . The corrosion resistance is higher than that of 45# steel due to combined effects of formation of austenite structure and refined dendrites, as well as disperse distribution of carbides. Moreover, composition distribution in the laser cladding layer is average, and the content of Fe element at the grain boundary is lower, and those of Cr, Mo elements at the boundary are higher than inside grain, while Ni element distributes homogeneously in the whole layer, which is beneficial to the improvement of ductility and corrosion resistance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503003 (2013)
Effect of Laser Shock Processing on Electrochemical Corrosion Behavior of AZ91 Magnesium Alloy
Li Shaozhe, Zhang Lingfeng, and Xing Qingpu
The effect of laser shock processing (LSP) on electrochemical corrosion behavior of AZ91 magnesium alloy in NaCl solution of mass fraction of 3.5% is studied by using electrochemical technique and transmission electron microscopy. The results show that a lot of dislocations reduce in the alloy after LSP. Impedance of AThe effect of laser shock processing (LSP) on electrochemical corrosion behavior of AZ91 magnesium alloy in NaCl solution of mass fraction of 3.5% is studied by using electrochemical technique and transmission electron microscopy. The results show that a lot of dislocations reduce in the alloy after LSP. Impedance of AZ91 magnesium alloy increases significantly and the electric current density reduces significantly after LSP. With the impact times of LSP increasing, the self-corrosion potential of AZ91 Mg alloy begin to move towards a positive direction, the corrosion current destiny declins while the corrosion resistance is improved in 3.5% NaCl solution..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503004 (2013)
Numerical Analysis for the Structure Effect on Stainless Steel Welding Treated by Laser Shock Processing
Yin Sumin, Zhang Chao, Wang Yun, Xu Zhenying, and Jiang Wenlin
In order to investigate the influence of laser shock processing on the residual stress distribution of stainless steel welding joint, the numerical analysis of the stainless steel welding process and laser shock processing weld is implemented. The results show that the residual stress distribution of welded structure iIn order to investigate the influence of laser shock processing on the residual stress distribution of stainless steel welding joint, the numerical analysis of the stainless steel welding process and laser shock processing weld is implemented. The results show that the residual stress distribution of welded structure is not uniform after welding, and the large residual tensile stress is produced on welding surface, meanwhile, the differences of welding residual stress between horizontal and vertical orientation are large. The residual stress of welding area is notably improved after laser shock processing, the residual stress on surface is changed from tensile residual stress into compressive residual stress, and the residual stress increases with laser power density and shocking times increasing. The residual stresses on horizontal and vertical orientation become uniform. The uniform residual stress can be induced with suitable overlapping rate. It provides a reference for the application of the laser shock processing in improving welding structure performance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503005 (2013)
Forming Ability of the Metal Foil Forming by Laser-Driven Multi-Layered Flyer
Wang Xiao, Liu Hui, Shen Zongbao, Zhou Jianzhong, Hu Yang, Du Daozhong, and Liu Huixia
Metal foil forming by laser-driven flyer is a novel high-speed micro-forming technology. The structure and performance of the flyer are the main factors affecting the forming ability and the workpiece quality of this technology. A series of experiments are carried out by a Spitlight 2000 NdYAG laser in order to investiMetal foil forming by laser-driven flyer is a novel high-speed micro-forming technology. The structure and performance of the flyer are the main factors affecting the forming ability and the workpiece quality of this technology. A series of experiments are carried out by a Spitlight 2000 NdYAG laser in order to investigate the effects of the multi-layered flyer [composed of absorbing layer (black acrylic paint), insulating layer (polyimide film) and aluminum flyer] on the formability of metal foil forming by laser-driven flyer. Experimental results show that the multi-layered flyer can increase the maximum deformation depth of the workpiece and attain better consistency of the workpiece and the mold. Therefore, the multi-layered flyer can magnify and equalize the shock wave pressure in the forming process, which leads to the improvement in forming ability and workpiece quality. The reasons for the improvement of the forming quality using multi-layered flyers are discussed. The effects of the laser energy and the polyimide film thickness on forming ability are also studied..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503006 (2013)
Study on the Characteristics of Double-Sided Laser Beam Welding for T-Joints
Yang Zhibin, Tao Wang, Liu Shen, Chen Jie, Chen Yanbin, Li Liqun, and Chen Lei
With the development of double-sided laser beam welding technique of aluminum alloy T-joints for domestic aircraft fuselage panels as the ground, the effects of welding parameters and laser posture on the welding seam formation quality are studied in details, and the microstructure characteristics of the T-joints are aWith the development of double-sided laser beam welding technique of aluminum alloy T-joints for domestic aircraft fuselage panels as the ground, the effects of welding parameters and laser posture on the welding seam formation quality are studied in details, and the microstructure characteristics of the T-joints are also preliminarily discussed. The experimental results show that it can realize the welding of T-joints for aircraft fuselage panels by double-sided laser beam welding and can obtain good welding appearance. In order to get adequate weld, the heat input will be controlled between 25 J/mm and 35 J/mm by matching laser power to suitable welding speed. Moreover, the wire feeding speed must be reasonable matched to guarantee the smooth transition of the weld surface. It is better to adopt low incident beam angle under the requests of weld penetration and fusion area, which is good for reducing the heat effects of the heat input. The optimal incident beam position is determined to be 0.2 mm on the stringer yielding a 45°～50° seam angle, and the maximum tensile strength reaches a maximum value. In order to keep the double-sided weld symmetry and improve the mechanical properties of T-joints, the beam separation distances must be strictly controlled to realize the double-sided welds fused in a common molten. Five distinct zones are identified which consist of the cellular dendrite zone, parallel dendrite zone, partially melted zone, over-aged zone, and base material. The partially melted zone become narrower further from the fusion zone center and which on the skin side is obviously than that on the stringer side..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503007 (2013)
Effect of Powder Properties on the Convergence of Powder Stream in Coaxial Laser Cladding
Liu Hao, Yu Gang, He Xiuli, and Li Shaoxia
The powder stream has an important influence on the quality of coating in coaxial laser cladding. In order to improve the convergence of powder stream, a numerical model of powder stream in coaxial laser cladding is developed based on a given coaxial nozzle. Simulations of three kinds of powder stream, including NiCoCrThe powder stream has an important influence on the quality of coating in coaxial laser cladding. In order to improve the convergence of powder stream, a numerical model of powder stream in coaxial laser cladding is developed based on a given coaxial nozzle. Simulations of three kinds of powder stream, including NiCoCrAlY, ZrO2 ceramic powder and W powder, are calculated and validated by the experimental results. The effect of powder properties, including particle diameter, shape, density and restitution coefficient, on the convergence of powder stream is investigated. According to the calculated results with the same powder feeding parameters, as the particle diameter increases, the powder flow focal distance decreases, and the powder concentration reaches a maximum within some particle diameter scale. The powder concentration gets bigger and the powder flow focal distance becomes shorter with the powder shape factor or powder density increasing. As restitution coefficient decreases, both powder flow distance and powder concentration increase..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503008 (2013)
Microstructure Characteristics and Mechanical Properties of Double-Sided Laser Beam Welded Aluminum Alloy T-Joints
Chen Yanbin, Yang Zhibin, Tao Wang, Chen Jie, Li Liqun, Liu Shen, and Chen Lei
The microstructure characteristics and mechanical properties of double-sided laser beam welded aluminum alloy T-joints for aircraft fuselage panels are systematically analyed. The experimental results show that five distinct zones are identified between the fusion zone center and the base material which consists cellulThe microstructure characteristics and mechanical properties of double-sided laser beam welded aluminum alloy T-joints for aircraft fuselage panels are systematically analyed. The experimental results show that five distinct zones are identified between the fusion zone center and the base material which consists cellular dendrite zone, parallel dendrite zone, partially melted zone, over-aged zone, and base material. The heat affected zone of the skin side is the weakest area. The tensile strength depends on the weld penetration, and the failure originates at the weld toe on the skin side. The average transverse and axial tensile strengths reach 87.8% and 53.1% of the base materials and the fracture mechanisms of the transverse and axial tensile tests are found to be ductile and brittle fracture, respectively. The average longitudinal tensile strength reaches 90.8% of the base materials, and the average elongation is 8.4% of the original test specimens. The dimples are small and shallow, the fracture is a mixture of ductile and brittle fracture, and a tearing trace near the fusion line appears. Fatigue failure is found to originate at the weld toe on the skin side and finally crack on the skin, and the conditioned fatigue strength is 80.7 MPa. The fracture at the weld toe is a mixture of ductile and brittle fracture, and the skin panel fracture appears brittle fracture feature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503009 (2013)
Research on the Variation Regularity of Single Laser Tracks Cross-Section Morphology During Laser Cladding
Gao Shiyou, Li Jian, Li Chenguang, and Zhou Yefei
The tracks cross-section morphological variaiton of single laser with the controllable processing parameters, such as laser power, scanning speed, and powder mass flow rate, is observed by means of the single laser cladding experiment. A curvilinear equation describing cross-section morphology controlled by a single paThe tracks cross-section morphological variaiton of single laser with the controllable processing parameters, such as laser power, scanning speed, and powder mass flow rate, is observed by means of the single laser cladding experiment. A curvilinear equation describing cross-section morphology controlled by a single parameter (δ=wtan β/2h) is proposed. According to the measurement datas of cross-section geometrical characteristic parameters: width w, height h, area F and deposition angle β, the functional relationship between the parameter δ and the nominal area Fm (Fm=wh) of the cross-section is established by applying the regression processing method. And the regularity of cross-section morphology is determined with the variation of Fm. The curvilinear equation of cross-section morphology is testified by the measurement datas of F and β..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 503010 (2013)
Laser Physics
Gain-Cavity Mode Detuning Vertical Cavity Surface Emitting Laser Operating at the High Temperature
Zhang Jianwei, Ning Yongqiang, Zhang Xing, Zeng Yugang, Zhang Jian, Liu Yun, Qin Li, and Wang Lijun
The situation of vertical cavity surface emitting laser (VCSEL) operating at high temperature is analyzed theoretically, and the gain-cavity mode detuning characteristics is employed to design the epitaxy structure of VCSEL. The metal-organic chemical vapor deposition (MOCVD) growth and fabrication process are carried The situation of vertical cavity surface emitting laser (VCSEL) operating at high temperature is analyzed theoretically, and the gain-cavity mode detuning characteristics is employed to design the epitaxy structure of VCSEL. The metal-organic chemical vapor deposition (MOCVD) growth and fabrication process are carried out. The barrier height above 0.25 eV is used in the active region of VCSEL to reduce the carrier leakage at high temperature. The designed structure employs the 11-nm gain-cavity mode deviation. The highest gain appeares at about 320 K, at which the minimum threshold current of VCSEL appears. The reflectivity of distributed Bragg reflector (DBR) within VCSEL is designed to obtain the low threshold current. The self-planar mesa structure is employed to fabricate the VCSEL devices. VCSEL with oxide apertures of 7, 9, 13 μm are fabricated. The threshold currents are 1.95, 2.53, 2.9 mA, respectively, and the corresponding maximum output powers are 0.31, 1.11, 1.04 mW at room temperature. The threshold current decreases first and then increased with the temperature increases, and the minimum value appears at 320～330 K. The measured results consist well with the gain-cavity characteristics of VCSEL..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502001 (2013)
Laser Diode End-Pumped Nd:YVO4 Self-Raman Laser at 559 nm with Sum-Frequency Mixing
Duan Yanmin, Zhu Haiyong, Feng Zhengrong, Zhang Yaoju, and Zheng Chongwei
Sum-frequency mixing of a laser diode end-pumped a-cut Nd:YVO4 self-Raman laser is reported. Reasonable designing of cavity construction and crystal coating, as well as choosing of sum-frequency mixing crystal are considered. The laser system is optimized for continuous-wave mode and Q-switched mode operation. ContinuoSum-frequency mixing of a laser diode end-pumped a-cut Nd:YVO4 self-Raman laser is reported. Reasonable designing of cavity construction and crystal coating, as well as choosing of sum-frequency mixing crystal are considered. The laser system is optimized for continuous-wave mode and Q-switched mode operation. Continuous-wave yellow-green laser with output power of 580 mW and wavelength of 558.6 nm is achieved at a pump power of 12 W, and the corresponding optical-optical conversion efficiency is about 5%. With pump power of 17.5 W and Q-switch repetition frequency of 30 kHz, yellow-green laser output power up to 1.71 W is achieved whose pulse width is 21 ns and optical-optical conversion efficiency is 9.8%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502002 (2013)
Cooling Technology of High-Power and High-Power Fiber Laser Amplifier
Dai Shoujun, He Bing, Zhou Jun, and Zhao Chun
Double-clading fiber coating thermal damage is one of the prime limiting factors for the operation of high-power continuous-wave (CW) fiber lasers. The thermal effects in high power CW fiber lasers are studied, and the maximum output power of fiber lasers limited by the thermal degradation of coatings is theoretically Double-clading fiber coating thermal damage is one of the prime limiting factors for the operation of high-power continuous-wave (CW) fiber lasers. The thermal effects in high power CW fiber lasers are studied, and the maximum output power of fiber lasers limited by the thermal degradation of coatings is theoretically simulated. Theoretical and experimental studies of splice points cooling in 1 kW CW fiber lasers are presented. Thermal contact resistances between the fiber and its heat sink are measured separately for different geometries and efficient cooling methods to achieve effective heat conduction are proposed. By using these optimized methods, based on the master oscillator power amplifier (MOPA) architecture, a 1080 nm 1.11 kW all-fiber laser prototype is obtained. The maximum surface temperature at the pump light launching end splice of the booster amplifier is 327 K (54 ℃). Moreover, thermal or nonlinear effects have not been observed during operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502003 (2013)
Study of Laser-Induced Damage in Fused Silica Irradiated by 351 nm Laser Near-Filed
Guo Yajing, Tang Shunxing, Tang Qing, Zhu Baoqiang, and Lin Zunqi
Damage experiments are conducted by irradiating 351 nm laser near-filed to fused silica based on the damage threshold definition of near-filed irradiating. Damage areas are extracted from damage images by the marker-based watershed algorithm with gray control. The initial damage threshold is defined as the fluence of cDamage experiments are conducted by irradiating 351 nm laser near-filed to fused silica based on the damage threshold definition of near-filed irradiating. Damage areas are extracted from damage images by the marker-based watershed algorithm with gray control. The initial damage threshold is defined as the fluence of critical site between damage region and no damage region, which is calculated by comparing the damage image with 351nm laser near-field. This damage testing method is sample, quick, which can effectively decrease the effect of beam diameter for damage threshold due to the bigger aperture. The algorithm of image segmentation effectively removes the noise and suppresses the over-segmentation, and improves the accuracy of initial damage and damage growth. The research shows that the damage of fused silica is induced by 351 nm laser near-field with pulse width of 3.13 ns. The initial damage threshold is 2.94 J/cm2. With multiple irradiation of fused silica, the damage growth of exit surface is exponential, and the coefficient of damage growth is 0.32..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502004 (2013)
Nd:LGS Laser Directly Pumped by Diode
Wang Qing, Wei Zhiyi, Wang Zhaohua, Li Dehua, Zhang Zhiguo, Zhang Huaijin, Wang Jiyang, Yang Junhong, and Ma Yunfeng
A 1.47 W 885 nm diode-pumped Nd:LGS laser at 1.06 μm is demonstrated by using a high quality Nd:LGS crystal. A corresponding optical-to-optical efficiency of 17.9%, the maximum slope efficiency of 21.4%, and a beam quality factor M2 of 1.21 and 1.22 for tangential direction and sagittal direction are obtained, respectiA 1.47 W 885 nm diode-pumped Nd:LGS laser at 1.06 μm is demonstrated by using a high quality Nd:LGS crystal. A corresponding optical-to-optical efficiency of 17.9%, the maximum slope efficiency of 21.4%, and a beam quality factor M2 of 1.21 and 1.22 for tangential direction and sagittal direction are obtained, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502005 (2013)
Evaluation of the Beam Quality of Supercontinuum Source Using Supercontinunm M2 Factor
Jin Aijun, Hou Jing, and Jiang Zongfu
Due to the wide spectra, the conventional methods can not evaluate the beam quality of the whole supercontinuum (SC). A new factor SC-M2 is introduced. The spectra of supercontinuum is obtained by solving the generalized nonlinear Schrdinger equation by the using of split-step Fourier method. The spectral centroid is Due to the wide spectra, the conventional methods can not evaluate the beam quality of the whole supercontinuum (SC). A new factor SC-M2 is introduced. The spectra of supercontinuum is obtained by solving the generalized nonlinear Schrdinger equation by the using of split-step Fourier method. The spectral centroid is calculated based on second-moment method. The near field optical power distribution of the supercontinuum source is obtained by the using of finite element method. After free space propagation, the far field distribution is obtained. Founded on the near field, far field and spectral centroid, the SC-M2 factor is defined to evaluate the beam quality of supercontinuum source as a whole. With this factor, the beam quality of supercontinuum source can be evaluated comprehensively and comparison among different supercontinuum sources can be made..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502006 (2013)
Dependence of the Rh6G Random Laser Behavior on Different Refractive Indices of Solvent
Yi Jiayu, Feng Guoying, Yang Liling, Yao Ke, Yang Chao, and Zhou Shouhuan
Rh6G random laser systems are obtained by choosing four solvents (methanol, ethanol, glycol, dimethylsulfoxide) with different refractive indices to disperse Rh6G mixed with 100 nm AlN spherical nanoparticles. It is experimentally investigated that the spectral and threshold characteristics of the Rh6G random laser behRh6G random laser systems are obtained by choosing four solvents (methanol, ethanol, glycol, dimethylsulfoxide) with different refractive indices to disperse Rh6G mixed with 100 nm AlN spherical nanoparticles. It is experimentally investigated that the spectral and threshold characteristics of the Rh6G random laser behaviors. As for the spectra, typical emission evolution spectra are observed. The peak positions vary with the change of solvents, and the reason for the variation is the absorption of the samples. For the threshold feature, the experimental results indicate that the threshold of the random laser depends on the refractive index of the surrounding solvents. The larger the refractive index of scatterers or smaller the refractive index of solvent is, the smaller the threshold will be. The theoretical explanation based on Mie scattering theory for this phenomenon is made. The low threshold random laser is attributed to low refractive index of solvent, which influences the scattering strength, leading to a smaller transport mean free path..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502007 (2013)
Propagation of Truncated Partially Coherent Cosh-Gaussian Beam in Non-Kolmogorov Turbulence
Tao Rumao, Si Lei, Ma Yanxing, Zhou Pu, and Liu Zejin
Propagation of partially coherent cosh-Gaussian beam in non-Kolmogorov turbulence is studied theoretically. Based on extended Huygens-Fresnel principle, the averaged intensity and the power in the bucket of partially coherent cosh-Gaussian beam in non-Kolmogorov turbulence are derived. The influence of beam parameters Propagation of partially coherent cosh-Gaussian beam in non-Kolmogorov turbulence is studied theoretically. Based on extended Huygens-Fresnel principle, the averaged intensity and the power in the bucket of partially coherent cosh-Gaussian beam in non-Kolmogorov turbulence are derived. The influence of beam parameters and turbulence parameters is studied numerically. The investigation presents a reference for engineering applications, for example the remote sensing and the free-space communication..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502008 (2013)
Discharge Parameters of Non-Chain Pulsed DF Laser
Pan Qikun, Xie Jijang, Ruan Peng, Zhang Laiming, Xie Jingjiang, Li Dianjun, Shao Chunlei, Yang Guilong, and Tan Gaijuan
The circuit parameters of spark pin ultroviolet (UV) pre-ionization discharge non-chain pulsed DF laser is researched to improve its discharge uniformity and electric energy depositions. Through analysis the process of dissociation of SF6 molecules and the attachment of electrons to SF6 molecules, the continuity-equatiThe circuit parameters of spark pin ultroviolet (UV) pre-ionization discharge non-chain pulsed DF laser is researched to improve its discharge uniformity and electric energy depositions. Through analysis the process of dissociation of SF6 molecules and the attachment of electrons to SF6 molecules, the continuity-equations for electrons is obtained. Combination with the Kirchhoff equations for discharge circuit, the mathematical model is established to describe the discharge parameters of DF laser. Based on this model, the voltage waveforms of pre-ionization and main discharge, also the current waveform of main discharge are solved numerically. The results display some physical processes correctly, such as the delay time between pre-ionization and main discharge, breakdown of the main electrode and the self-maintained discharge. Then the corresponding experiments are carried out to verify the results of this model. The measured pre-ionization and main discharge voltage waveforms are consistent with the simulation results. Using this model, the influences of main store capacitance, delay inductance, peak capacitance on the discharge are researched individually, and the circuit parameters of DF laser are obtained that is useful to improve the discharge stability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502009 (2013)
Fluorescence Emission from a 355-nm Laser Pumped Double-Cladding Erbium-Doped Fiber
Zhao Junqing, Ruan Shuangchen, Guo Chunyu, and Zhang Min
Using a 355-nm laser to pump a home-made double-cladding erbium-doped fiber (DC-EDF), visible and near-infrared fluorescence emissions are obtained. For a 8-m long DC-EDF, visible fluorescence can cover the wavelength region from 375 nm to 800 nm under 429 mW launched pump power, in which the fluorescence peaks are at Using a 355-nm laser to pump a home-made double-cladding erbium-doped fiber (DC-EDF), visible and near-infrared fluorescence emissions are obtained. For a 8-m long DC-EDF, visible fluorescence can cover the wavelength region from 375 nm to 800 nm under 429 mW launched pump power, in which the fluorescence peaks are at 397.24, 415.06, 456.30, 497.35, 549.49, 678.26 nm. The near-infrared fluorescence ranges from 1429.25 nm to 1667.75 nm. The peaks and band-widths in the near infrared region are strongly dependent on the length of the DC-EDF. We also observe the broadening of bandwidth when the launched pump power is enhanced. Our results demonstrate that the 355-nm laser can be utilized to pump EDF, which provides a new approach for the traditional EDF light sources. Development of light sources operating at new-wavelength band is possible according to experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 502010 (2013)
Materials and Thin Films
Energy Transfer Mechanisms of Ce3+/Tb3+ Doped Scintillating Glasses with High [Gd(1-x)Lux]2O3 Concentration
Yang Bin, Wang Qian, Xia Haiping, Wang Jinhao, and Zhang Yuepin
The Ce3+/Tb3+ doped oxyfluoride glasses with high Gd[(1-x)Lux]2O3 concentration are prepared by high temperature melting method. The densities, transmission spectra, excitation spectra, emission spectra under ultraviolet (UV) and X-ray excitations and decay curves of Ce3+ ions are measured and analyzed. The scintillatiThe Ce3+/Tb3+ doped oxyfluoride glasses with high Gd[(1-x)Lux]2O3 concentration are prepared by high temperature melting method. The densities, transmission spectra, excitation spectra, emission spectra under ultraviolet (UV) and X-ray excitations and decay curves of Ce3+ ions are measured and analyzed. The scintillating glasses have excellent performance of high light output. The densities of the glasses are greater than 5.8 g/cm3. The Ce3+ ions can sensitize the luminescence of Tb3+ ions. The energy transfer mechanisms of the Ce3+/Tb3+ doped scintillating glasses are analyzed by the I-H theory model. The energy transfer rate and energy transfer efficiency between Ce3+ and Tb3+ ions are calculated by the fitting data and theoretical formula. The results indicate that the energy transfer mechanism is non-radiative energy transfer, the energy transfer rate is proportional to the square of the Tb3+ ions concentration, and energy transfer efficiency increases with the concentration of Tb3+ ions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 506001 (2013)
Effect of Defocus Distance on Morphology of Gaussian Distributed Laser Induced Forward Transfer Cu Film and Mechanism Analysis
Liu Wei, Dou Guangbin, Wang Chunqing, Tian Yanhong, and Ye Jiaotuo
As a method of micro fabrication, laser induced forward transfer (LIFT) can be used to make microstructures. Presently, it has become a popular issue on microfabrication process. In this study, a Cu thin film is transferred from one quartz substrate to another quartz substrate by regulating the defocus distance of GausAs a method of micro fabrication, laser induced forward transfer (LIFT) can be used to make microstructures. Presently, it has become a popular issue on microfabrication process. In this study, a Cu thin film is transferred from one quartz substrate to another quartz substrate by regulating the defocus distance of Gaussian distributed laser beam. The transferred Cu thin film is processed by optical microscope, scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analyzing. Relationship between defocus distance of the laser beam and size, morphology and uniformity of transferred Cu film is discussed. Moreover, mechanism of the morphology transition is analyzed based on the results. The results indicate that with the increase of defocus distance, the size of transferred Cu patterns increase firstly, then decrease, and disappear at last. Morphology of the transferred Cu patterns transforms from crater-shape to plane with many tiny Cu particles at the edge of the patterns. In addition, the transfer form of the thin film changes from liquid transfer to solid transfer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 507001 (2013)
Research of Ultraviolet Induced Transmission Filter for the Solar Blind System
Fu Xiuhua, Kou Yang, Liu Dongmei, Tang Heyue, and Wang Shuai
Researches of ultraviolet band optical thin films are significant important in both military and civilian fields. Domestic and international researches about ultraviolet film often use high and low refractive index materials to alternately plat dielectric layer structures. The disadvantage is that the cutoff level in vResearches of ultraviolet band optical thin films are significant important in both military and civilian fields. Domestic and international researches about ultraviolet film often use high and low refractive index materials to alternately plat dielectric layer structures. The disadvantage is that the cutoff level in visible band is not good, so there will be large amount of background noise. Aim at this problem, this paper uses the coating design theory and adopts an induced transmission filter structure based on the thin film of ultraviolet material properties, coating optimization design technology, deposition and testing technology. Through repeated theoretical calculation and simulation experiments, process parameters of different materials are optimized. We deposit the ultraviolet induced filter which transmits at 265 nm and cutoffs at 300～1000 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 507002 (2013)
Measurement and Metrology
Smart and Quantitative Near-Infrared Point-Diffraction Interferometer Based on the Self-Referencing Wavefront Sensor
Yang Pengqian, Stefan Hippler, Casey Deen, Wolfgang Brandner, Sarah Kendrew, Miao Jie, Zhang Yanli, and Zhu Jianqiang
This paper describes the development of a novel infrared point-diffraction interferometer (IPDI), which can be readily applied to real-time quantitative phase measurement. We generate reference wave with the help of Michelson-like unit combined with a low-pass spatial filter, and extract the phase information using winThis paper describes the development of a novel infrared point-diffraction interferometer (IPDI), which can be readily applied to real-time quantitative phase measurement. We generate reference wave with the help of Michelson-like unit combined with a low-pass spatial filter, and extract the phase information using windowed Fourier transform algorithm from single off-axis fringes. The arrangement of the proposed setup offers a quasi-common-path geometry, which could significantly minimize the systematic errors. The proposed method of IPDI is effective and sufficient for the dynamic process measurement of small deformation with higher spatial resolution compared with the conventional off-axis scheme. The feasibility of the proposed setup is demonstrated, followed by methods of reconstruction and system calibration. The nanoscale repeatability is achieved in our experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508001 (2013)
Research on Large Open Stockyard Laser Measurement Methods
Wang Haibo, Zhang Dejin, and He Li
Artificial measuring point measurement method is used for measurement in large open-air stockyard because of no carrier installed measurement equipment, which can result in low efficiency, long life cycle, poor accuracy and man-made influence. To solve above problem, telescoping mechanism installation on the vehicle plArtificial measuring point measurement method is used for measurement in large open-air stockyard because of no carrier installed measurement equipment, which can result in low efficiency, long life cycle, poor accuracy and man-made influence. To solve above problem, telescoping mechanism installation on the vehicle platform is proposed. Laser scanner, inertial navigation, GPS and electronic pan/tilt/zoom (PTZ) are integrated, and partition independent scanning measurement of stockyard and unified coordinate transformation combination are used to quick access to the stockyard 3D coordinate data and to accurately calculate the size of the stockyard enabling reserves converter. Under test conditions, the absolute accuracy is up to 0.4%. Open yard field tests show that the separated ten districts measurement of 8000 m2 can be completed within one hour with the error of repeating measurement less than 0.9%. Field test of mine surveying isn′t taken and the accuracy is lower than the above conclusions based on the device parameters, but it can meet the measurement need of the industry. This method is an effective solution to the measurement problem, and can be widely used in the open yard, mine surveying, with good application and promotion prospects..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508002 (2013)
White Light Interferometry for Pigtail Polarization Crosstalk of Ti-Diffused LiNbO3 Integrated Optic Phase Modulator
Li Chuansheng, Zhang Chunxi, Wang Xiaxiao, Li Lijing, Yu Jia, and Feng Xiujuan
A new test method for the pigtail polarization crosstalk of the Ti-diffused LiNbO3 integrated optic phase modulator(TiLiNbO3 IOPM) is proposed based on the white-light interferometry. The white light interference intensity as a function of the alignment angle between the integrated optic chip and the polarization-maintA new test method for the pigtail polarization crosstalk of the Ti-diffused LiNbO3 integrated optic phase modulator(TiLiNbO3 IOPM) is proposed based on the white-light interferometry. The white light interference intensity as a function of the alignment angle between the integrated optic chip and the polarization-maintaining pigtail and the azimuth of the polarizer is theoretically analyzed. It is shown by the digital simulation that the pigtail polarization crosstalk of the IOPM can be obtained by the peaks of the interference envelope associated with the polarization coupling points of the IOPM. The pigtail polarization crosstalk of the TiLiNbO3 IOPM is tested by utilizing the white light interferometry, and the apparent interference peaks are exhibited at the polarization coupling points. The input and output pigtail polarization crosstalk are -34.5 dB and -23.3 dB respectively at room temperature, and decrease as the temperature rises from -40 ℃ to 60 ℃. The feasibility of the white light interferometry is verified by the experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508003 (2013)
Laser Stripe Center Extraction Based on Cross-Correlation Algorithm
Liu Zhen, Li Sheng, and Feng Chang
In line structured light vision measurement, the extraction accuracy and precision of the light stripe center point directly affects the final accuracy of the measurement results. The contradiction between high capacity of anti-interference, good robustness and intensive computation exists in optical center extraction In line structured light vision measurement, the extraction accuracy and precision of the light stripe center point directly affects the final accuracy of the measurement results. The contradiction between high capacity of anti-interference, good robustness and intensive computation exists in optical center extraction algorithm, so a cross-correlation stripe center extraction algorithm is proposed. The gradient threshold is used to separate the effective stripes region, and correlation is applied between cross-correlation coefficient and corresponding gray scale. The stripe with cross-correlation′s extreme value is selected as the initial center, and then the curve fitting method is used to refine the accurate stripe center. Here the cross-correlation′s value is used to evaluate whether the stripe center exists or not, and the similarity constraints of gray scale and position in the neighborhood stripes are employed to eliminate the noise. The experimental results show that the algorithm has high stripe extraction accuracy and calculation speed. Compared with current algorithms, it is simple and practical, and also has good robustness and the ability of anti-noise repair on disconnected stripes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508004 (2013)
Refraction Index Measurement of Transparent Liquid by Single-Element Interferometer
Luo Wenquan, Feng Guoying, and Du Yongzhao
Refraction index is one of the most important parameters in investigating the thermal effect of liquid laser. Interferometer technique is one of the most common types of the refraction index measurement, but it is sensitive to disturbances. An experimental method for the refraction index measurement of transparent liquRefraction index is one of the most important parameters in investigating the thermal effect of liquid laser. Interferometer technique is one of the most common types of the refraction index measurement, but it is sensitive to disturbances. An experimental method for the refraction index measurement of transparent liquid is presented, based on the single-element interferometer. The interference pattern is captured by a CCD camera. The method is simple as well as stable, which can be easily interpreted geometrically. The accuracy of the refractive index measurement is of the order of 10-4.Compared to the Michelson interferometer, it replies that the stability of the single-element interferometer is better than the typical interferometer′s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508005 (2013)
Analysis of Measurable Size Range and Its Measuring Accuracy of Particle in Interferometric Particle Imaging System
Lü Qieni, Lü Tong, Jin Wenhua, and Chen Yiliang
According to the measurement equation of interferometric particle imaging(IPI), the influence factors including the maximum and the smallest measurable particle diameters and its measuring accuracy of particle diameter, are analyzed in IPI optical system. For the given CCD, imaging lens, wavelength of illumination lighAccording to the measurement equation of interferometric particle imaging(IPI), the influence factors including the maximum and the smallest measurable particle diameters and its measuring accuracy of particle diameter, are analyzed in IPI optical system. For the given CCD, imaging lens, wavelength of illumination light and the thickness of the laser width, the influence of the object distance and defocusing distance on the size of the interference pattern of a particle is thoroughly analyzed, the measuring accuracy and the measurable range of particle size are then investigated. The result is that the relatively larger collection angle should be used as much as possible on the condition that the requirements of the measurable size range are satisfied. The larger the size of the interference pattern, the smaller the measuremental error of particle size with the finger overlap considered, and the sub-pixel accuracy of the number of fringes/finger spacing is acquired by interpolation. The optical system design example and its test results of the standard particle are given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 508006 (2013)
Optical Communication
Study of Fiber Bragg Grating Fabrication Online on Draw Tower via Phase Mask Method and Equipment Manufacturing
Yu Hua, He Wei, Guo Huiyong, Li Xiaofu, Feng Bo, and Yu Xuan
Fiber Bragg grating (FBG) fabrication on a draw tower can form a one-dimensional array of FBGs on a single fiber without welding spot between gratings, and is beneficial to build a massive sensor network. Phase mask method is employed to fabricate FBG online on a draw tower, by which we can precisely control the Bragg Fiber Bragg grating (FBG) fabrication on a draw tower can form a one-dimensional array of FBGs on a single fiber without welding spot between gratings, and is beneficial to build a massive sensor network. Phase mask method is employed to fabricate FBG online on a draw tower, by which we can precisely control the Bragg wavelength of FBG. A set of device is developed according to the characteristics of inscribing FBG by using phase mask method and the requirements of writing FBG on a draw tower. An array of 164 FBGs is produced on a single fiber by using this device..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 505001 (2013)
Fabrication Technology of Phase Shifted Fiber Bragg Grating with an Arc Discharge Technique
Liu Xuejing, Yang Yuanhong, Zhang Xiaozhe, and Jin Wei
Electric arc discharge erasing (ADE) effect, which can erase the refractive index modulation in fiber Bragg gratings (FBGs), is demonstrated. Based on ADE technique, the phase-shifted fiber Bragg grating (PSFBG) is fabricated successfully. According to the characteristics of the ADE effect, the theoretical model of PSFElectric arc discharge erasing (ADE) effect, which can erase the refractive index modulation in fiber Bragg gratings (FBGs), is demonstrated. Based on ADE technique, the phase-shifted fiber Bragg grating (PSFBG) is fabricated successfully. According to the characteristics of the ADE effect, the theoretical model of PSFBGs produced by this process is built, based on the changes of FBG refractive index and erased length by arc discharges. A comprehensive simulation study is conducted under different FBG parameters. The specific fabrication setup is designed, and the fabrication technique of PSFBG based ADE is studied experimentally. The evolution of the PSFBGs′ main parameters, including the wavelength, the intensity and the bandwidth of transmission peak, is investigated experimentally under various conditions, which include changes of the strain, the parameters of electric arc discharge, the properties of the FBGs and annealing treatment factors. The theoretical simulation and experimental study are consistent. It is shown that the PSFBG fabrication technique based on ADE is convenient and effective, and high-quality PSFBG can be produced by optimizing the parameters of arc discharges and FBGs..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 505002 (2013)
Fiber Length Measurement System Based on Phase Modulation Optical Link
Ye Quanyi, and Yang Chun
Based on phase modulation optical link, a novel fiber length measurement system is proposed. The theory model of gain of optical link is derived. By analyzing the relationship between the free spectral range of gain of the optical link and the optical path difference of the fiber interferometer, the fiber length is acqBased on phase modulation optical link, a novel fiber length measurement system is proposed. The theory model of gain of optical link is derived. By analyzing the relationship between the free spectral range of gain of the optical link and the optical path difference of the fiber interferometer, the fiber length is acquired. Compared with the traditional time domain reflectometry (OTDR), this system has no dead zone, and improves the precision from meter to millimeter. Compared with optical frequency domain reflectometry (OFDR) and optical coherence domain reflectometry (OCDR), this system does not need costly and high-performance laser to ensure coherence. The feasibility of the system is analyzed in theory, and is verified by experiments. It is shown that the smallest measurable relative length of fiber is 3 mm with the existing 67 GHz vector network analyzer, and the error can be controlled within 0.05 mm when the relative length of fiber is 100 m. This system is characterized by simple structure, easy operation and higher practical value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 505003 (2013)
Simulation Research of Laser Beam Atmospheric Propagation in Free-Space Optical Communication
Zhai Chao, Wu Feng, Yang Qingbo, Tan Liying, and Ma Jing
Numerical simulation has advantages over theoretical and experimental research of controllable parameters and realizing ensemble average. Therefore, numerical simulation can be used to study the influence of atmospheric turbulence in big elevation link and other fields which can′t be built in experimental system. UsingNumerical simulation has advantages over theoretical and experimental research of controllable parameters and realizing ensemble average. Therefore, numerical simulation can be used to study the influence of atmospheric turbulence in big elevation link and other fields which can′t be built in experimental system. Using Zernike polynomial method and multi-layer phase screen theory, the atmospheric multi-layer phase screen model is established. The numerical simulations of Gaussian beam propagating in horizontal link (0°) and big elevation link (30°,60°) are achieved. Using the empirical formula for the variance of angle of arrival (AOA) fluctuations in horizontal link, the results of three groups of 900 times numerical simulation in horizontal link are analyzed. The results show that the error of variances of AOA fluctuations between simulation and experimental values is within 5%, and this model is effective. This work is important for studying the influence of atmospheric turbulence in free-space optical communication system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 505004 (2013)
Remote Sensing and Sensors
Research on Fusion of 3D Laser Point Clouds and CCD Image
Shao Jie, Zhang Aiwu, Wang Shumin, Meng Xiangang, Yang Lingbo, and Wang Zhihua
A fusion method of laser scanning and image is put forward. In this method, accurate matching point is obtained by stereo image matching firstly, and the adjacent iterative registration is finished with three-dimensional (3D) scanning points. In the searching of K adjacent point by grid partition method, the option iteA fusion method of laser scanning and image is put forward. In this method, accurate matching point is obtained by stereo image matching firstly, and the adjacent iterative registration is finished with three-dimensional (3D) scanning points. In the searching of K adjacent point by grid partition method, the option iteration of Euclidean distance is used to gradually realize the accurate registration of image points and laser scanning points. Using the space resection for correct elements of exterior orientation, through the collinear relationship of projective center, image point and laser point, pixel location of laser point in the corresponding image is realized, and color attribute information is obtained. The experimental results show that the algorithm not only has a better performance to realize the accurate fusion of 3D surface laser points with CCD image, but also is feasible and effective for the fusion of airborne laser data with image..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 514001 (2013)
Spectroscopy
Fast Spectral Rebuild Garithmetic of PEM-FTS Nolinear Phase Interfergram Data
Zhang Minjuan, Wang Zhaoba, Wang Zhibin, Li Xiao, Wang Mingyan, and Li Jinhua
The optical difference variation of the photoelastic modulate fourier transform spectrometers (PEM-FTS) is sinusoidal and high-speed, so more than 105 interferograms per second is acquired. In order to fleetly and accurately recover the spectrums of the signals which are sampled by equal interval, the cubic spline inteThe optical difference variation of the photoelastic modulate fourier transform spectrometers (PEM-FTS) is sinusoidal and high-speed, so more than 105 interferograms per second is acquired. In order to fleetly and accurately recover the spectrums of the signals which are sampled by equal interval, the cubic spline interpolation algorithm, nonuniform discrete Fourier transform (NDFT) with phase compensation algorithm, and accelerating nonuniform fast Fourier transform (NUFFT) algorithm are applied in the data processing system of PEM-FTS. It is found that the accelerating NUFFT is fast, and its speed is an order of magnitude higher than that of NDFT with phase compensation, and two times of that of the FFT with cubic spline interpolation algorithm. The advantage of the method is obvious when the number of sampling points is increased. And the precision of the method is high with its deviation less than 0.00054. The method can be applied in PEM-FTS..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 515001 (2013)
Laser Temperature Compensation Used in Tunable Diode-Laser Absorption Spectroscopy
Yuan Song, Kan Ruifeng, He Yabai, Yao Lu, Chen Jiuying, Xu Zhenyu, Li Han, Ruan Jun, He Junfeng, and Wei Min
Tunable diode-laser absorption spectroscopy(TDLAS) has a good prospect of application, such as environmental monitoring, industrial process detection, due to its high resolution, high sensitivity and rapid measurement. But the wavelength of laser shifts with the change of ambient temperature when the system is working Tunable diode-laser absorption spectroscopy(TDLAS) has a good prospect of application, such as environmental monitoring, industrial process detection, due to its high resolution, high sensitivity and rapid measurement. But the wavelength of laser shifts with the change of ambient temperature when the system is working continuously for a long period of time. Aim at this problem, the wavelength variation with the change of temperature and the quantitative impact on spectral processing is studied. In order to eliminate the shift of wavelength, ADμC841 is used for temperature compensation, this system can re-set the temperature of the laser according to the ambient temperature to lock the laser spectrum. The experiment in temperature-controlled device at the temperature of 20 ℃～60 ℃ shows that the shift of laser wavelength is about 4.1 pm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 5, 515002 (2013)
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