Journals >Chinese Journal of Lasers
Contents
2016
Volume: 43 Issue 12
34 Article(s)
Export citation format
[in Chinese]
Research on Defect Solitons in Kagome Photonic Lattices in Centrosymmetric Photorefractive Crystals
Zhang Baoju, Lu Keqing, Zhao Chong, and Gao Lixu
Defect solitons and their stability are reported in Kagome photonic lattices in centrosymmetric photorefractive crystals. These defect solitons exist in different gaps due to the change of defect intensity. When the defect is positive, these defect solitons exist only in the semi-infinite gap. By using the perturbationDefect solitons and their stability are reported in Kagome photonic lattices in centrosymmetric photorefractive crystals. These defect solitons exist in different gaps due to the change of defect intensity. When the defect is positive, these defect solitons exist only in the semi-infinite gap. By using the perturbation growth rate and beam propagation method, the stability of these defect solitons is investigated. The analysis indicates that the stability of these defect solitons tested by the perturbation growth rate and beam propagation method is same, the positive defect solitons are stable in the low power region and unstable in the high power region. When the defect is negative, these defect solitons exist both in the semi-infinite gap and the first gap. Negative defect solitons in the semi-infinite gap are stable in the moderate power region and unstable in the high and low power regions. In the first gap, the negative defect solitons are always stable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1208001 (2016)
Characteristics of Single Resonant Nanosecond Pulse Optical Parametric Oscillator with Output Wavelength of 2.05 μm
Xie Xiaobing, Li Shiguang, Zhu Xiaolei, Zhang Junxuan, Dong Yijing, and Chen Weibiao
A KTP crystal extra-cavity single-resonant optical parametric oscillator (OPO) pumped by 1064 nm single-frequency laser is reported, and the nanosecond laser pulse output with wavelength of 2.05 μm is obtained. In the plane-parallel cavity, two type II phase-matched KTP crystals are placed in walk-off-compensated mode.A KTP crystal extra-cavity single-resonant optical parametric oscillator (OPO) pumped by 1064 nm single-frequency laser is reported, and the nanosecond laser pulse output with wavelength of 2.05 μm is obtained. In the plane-parallel cavity, two type II phase-matched KTP crystals are placed in walk-off-compensated mode. When the pump single pulse energy reaches 5 mJ at repetition frequency of 400 Hz, a 2.05 μm signal laser output with single pulse energy of 0.9 mJ is obtained, whose pulse width is about 3.7 ns, the corresponding conversion efficiency is about 18% from pump light to signal light, and the beam quality factor M2 are 2.08, 3.03 in x, y directions, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1208002 (2016)
Beam Transmission and Control
Beam Alignment and Convergence Analysis of Scanning Beam Interference Lithography Systems
Wang Wei, Bayanheshig, Song Ying, Jiang Shan, and Pan Mingzhong
Beam alignment is one of the key techniques in the scanning beam interference lithography system. The coincidence degree between the position and the angle of two exposure beams directly affects the groove quality of the produced grating mask. In view of the mutual coupling between the two dimensions of motion in beam Beam alignment is one of the key techniques in the scanning beam interference lithography system. The coincidence degree between the position and the angle of two exposure beams directly affects the groove quality of the produced grating mask. In view of the mutual coupling between the two dimensions of motion in beam adjustment, the convergence condition of the alignment algorithm is derived, and the influence of assembly error between the reflector and the decoupling plane on the alignment performance is analyzed. The analysis shows that due to the presence of assembly error, the performance of the beam alignment system declines, and even leads to the divergence of the alignment algorithm. The convergence of the system can be optimized by adjusting the ratio L2/L1, where L1 is the distance between mirror M1 and decoupling plane, and L2 is the distance between mirror M2 and decoupling plane. The experimental results show that when L2/L1 is large, performance of the alignment system is poor and the convergence is slow. When L2/L1 is relatively small, the beam alignment system can quickly converge to the target position, and the alignment of the beam is effective. The deduction and simulation analysis can provide theoretical guidance for the design of beam alignment systems and whole exposure light paths..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1205001 (2016)
Influence of Axicon Vertex off Axis Machining Error on Bessel Beams
Hu Run, and Wu Fengtie
The transmittance function of the axicon vertex off axis machining error is derived theoretically. Based on Huygens-Fresnel diffraction integral theory and stationary phase method, the expression of diffraction field behind the vertex off axis machining error is derived and the influence of the vertex off axis machininThe transmittance function of the axicon vertex off axis machining error is derived theoretically. Based on Huygens-Fresnel diffraction integral theory and stationary phase method, the expression of diffraction field behind the vertex off axis machining error is derived and the influence of the vertex off axis machining error in an axicon on the Bessel beams is analyzed. The expression of diffraction field behind the axicon is simulated numerically. Results show that if the axicon is ideal manufactured, the field distribution behind the axicon is approximately an ideal Bessel beam, and if the machining error exists, the diffraction beam pattern will split in half. At the same distance, the separation of the beam pattern will increase with the increasing of the vertex off axis machining error, with the same vertex off axis machining error, the separation of the beam pattern will increase with the increasing of the transmission distance. Meanwhile, the influence of the thickness of the element on the separation of the beam pattern is also studied. The results show that the separation degree of the beam pattern increases gradually with the increasing of the thickness. The findings offer some guidance for axicon machining and the application of Bessel beams, and so forth..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1205002 (2016)
Laser Devices and Laser Physics
Beam Homogenized Shaping and Speckle Suppression in Laser Projection Display System Using Liquid Crystal on Silicon
Liang Chuanyang, Zhang Wei, Rui Dawei, Sui Yongxin, and Yang Huaijiang
Laser projection display usually need to solve the issues of beam shaping homogenization and speckle suppression. This paper proposes a method that liquid crystal on silicon (LCoS) spatial light modulator (SLM) is used to solve the problems simultaneously. The idea of fine design for diffractive optical element (DOE) iLaser projection display usually need to solve the issues of beam shaping homogenization and speckle suppression. This paper proposes a method that liquid crystal on silicon (LCoS) spatial light modulator (SLM) is used to solve the problems simultaneously. The idea of fine design for diffractive optical element (DOE) is used to design phase distribution of DOE that needs to be shaped, which can control the intensity distribution of sampling points and other points. The circular Gaussian laser illumination beam is shaped into a flat-top rectangular profile. Under different initial phase conditions, the designed DOEs generate diffraction patterns with the same intensity distributions and different phase distributions. When diffraction patterns are modulated by SLM and they are overlapped by time integral, the uniformity of illumination spot can be improved, and image speckles can be suppressed. The simulation results show that by overlapping 16 diffraction patterns, the proposed method can improve the uniformity from 74% to 92.57%, and reduce the speckle contrast of the screen from 0.991 to 0.2508. The proposed method has high stability, low power consumption and small size, which provide good reference for display structure of pico-projector..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1201001 (2016)
Bidirectional Hybrid Mode-Locking Erbium-Doped Fiber Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A bidirectional hybrid mode-locking erbium-doped fiber laser is constructed. The reflective semiconductor saturable absorber mirror and the nonlinear polarization rotation effect are employed as hybrid mode-locking mechanism in the σ-shaped cavity without isolation device. The stable self-starting bidirectional mode-loA bidirectional hybrid mode-locking erbium-doped fiber laser is constructed. The reflective semiconductor saturable absorber mirror and the nonlinear polarization rotation effect are employed as hybrid mode-locking mechanism in the σ-shaped cavity without isolation device. The stable self-starting bidirectional mode-locking operation is achieved by finely adjusting the laser spot size focused on the semiconductor saturable absorber mirror and the angle of intracavity wave plates. The laser operates in soliton mode-locking state, and the two counter circulating pulses are output by two polarization beam splitters, respectively. The repetition rates of two pulse trains are both 60.72 MHz. The output powers of counter clockwise light and clockwise light are 23.7 mW and 1.3 mW, and their signal to noise ratios are 67.5 dB and 66.5 dB, respectively. The difference between counter clockwise and clockwise output powers is large, which is caused by the mode-locking mechanism..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1201002 (2016)
Effect of Water Mist on Threshold and Damage of Dentin Ablation with Q-Switched Er:YAG Laser
Cui Qingzhe, Wei Meng′en, Ling Lin, Cheng Tingqing, Wu Xianyou, and Jiang Haihe
The effect of water mist on the extracted dentin ablation by Q-switched Er:YAG laser is investigated, and the influence of water mist on the ablated dentin microstructure is studied. The Q-switched Er:YAG laser with 62 ns pulse width is used to ablate the human dentin at the repetition rate of 3 Hz, the number of pulseThe effect of water mist on the extracted dentin ablation by Q-switched Er:YAG laser is investigated, and the influence of water mist on the ablated dentin microstructure is studied. The Q-switched Er:YAG laser with 62 ns pulse width is used to ablate the human dentin at the repetition rate of 3 Hz, the number of pulses is 10, and the energy range is from 4 mJ to 70 mJ. Different flow rates of water mist (0, 4, 9, 13 mL/min) are applied during the experiments. 10 dentin samples are ablated under each experimental condition. A scanning electron microscope is used to observe the microstructures of ablated holes. The experiment result shows that the increase of flow rate of water mist makes the Q-switched Er:YAG laser ablation threshold to dentin rise, and the dentin is protected from mechanical damage. The results are guided for acquiring microstructures during dentin ablation with Q-switched Er:YAG laser and practical treatment in dentistry..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1201003 (2016)
Ultra-Narrow Linewidth Random Fiber Laser Based on All Grating Fiber
Xu Ruquan, Guo Huiyong, Li Wei, and Liang Lei
A narrow linewidth random fiber laser (RFL) using all grating fiber (AGF) as the random feedback media is designed and verified. A 130 m AGF is fabricated on the single mode optical fiber core which is made online by the drawing tower based on the phase mask method. Total 4.3×105 fiber Bragg gratings (FBG) with 0.A narrow linewidth random fiber laser (RFL) using all grating fiber (AGF) as the random feedback media is designed and verified. A 130 m AGF is fabricated on the single mode optical fiber core which is made online by the drawing tower based on the phase mask method. Total 4.3×105 fiber Bragg gratings (FBG) with 0.3 mm grating length are made on the 130 m AGF. The AGF is incorporated into a ring laser cavity consisting of an erbium-doped fiber amplifier, a fiber isolator and a narrow band optical filter via an optical circulator, and then a ring RFL is established. Results show that the RFL based on AGF can output continuous single mode laser with the maximum power of 1.26 mW when the RFL mode is selected by the narrowband optical filter. The threshold current is 75 mA and the slope efficiency is 56%. The RFL based on AGF with the narrow linewidth of 1.25 kHz and the optical signal-noise-rate of 75 dB is achieved with a 100 mA pump current. The relative intensity noise is -90 dB when the frequency is beyond 1 kHz. Compared with the traditional RFL feedback cavity which is based on discrete FBG, the RFL feedback cavity based on AGF can provide more random feedback points and more uniform randomness, which contributes to obtaining narrow linewidth for RFL..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1201005 (2016)
Design and Application of Nd:Glass Disc-Amplifier as Pump Source of 5 PW Ti:Sapphire Chirped Pulsed Amplifier
Xu Lu, Yin Dingjun, Lu Haihe, Yu Lianghong, Chu Yuxi, Gan Zebiao, Li Jinfeng, and Liang Xiaoyan
Based on the Monte Carlo rays tracing method, the three dimensional numerical model of pump distribution in Nd:glass disc amplifier is developed. In addition, combined with the other numerical models of Xe flashlamp charge/discharge circuit, amplified spontaneous emission, and laser pulse amplification, the whole work Based on the Monte Carlo rays tracing method, the three dimensional numerical model of pump distribution in Nd:glass disc amplifier is developed. In addition, combined with the other numerical models of Xe flashlamp charge/discharge circuit, amplified spontaneous emission, and laser pulse amplification, the whole work process of Nd:glass disc-amplifier is numerical simulated in detail to realize the whole process of the energy storage to the amplifying of Nd:glass disc amplifier. Based on the results of numerical simulation, the designed Nd:glass disc amplifier is used in the experiments of 5 PW Ti:sapphire chirped pulse amplifier, and the experimental results are in good accordance with the calculated consequence..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1201006 (2016)
Laser Manufacturing
Effect of Surface Treatment Technology on Laser Damage Resistance of Aluminium Alloy
Shi Shuang, Sun Mingying, Hao Yanfei, Zhang Yan, Pang Xiangyang, Zhang Yanan, and Liu Zhigang
The effect of surface treatment technology on laser damage resistance of aluminum alloy is studied. Results show that， under the same nanosecond laser irradiation, the laser-induced damage threshold of nickel-plated metal surface, black anode oxidated surface, or hard anode oxidated surface is lower, while that of inacThe effect of surface treatment technology on laser damage resistance of aluminum alloy is studied. Results show that， under the same nanosecond laser irradiation, the laser-induced damage threshold of nickel-plated metal surface, black anode oxidated surface, or hard anode oxidated surface is lower, while that of inactivated or micro arc oxidized surface is higher, if compared with that of mechanically polished surface; surfaces treated by the same treatment process but with different parameters have different damage thresholds. With the comparison among the relevant physical parameters of different technologies, the damage thresholds, morphologies, and patterns are analyzed and the results indicate that the inactivation technology is more suitable for the aluminum alloy surface treatment in high power laser facility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202001 (2016)
Optimal Design of Support Structures in Selective Laser Melting of Parts
Zhang Guoqing, Yang Yongqiang, Zhang Zimian, Song Changhui, Wang Anmin, and Yu Jiakuo
Warping deformation often occurs during the process of selective laser melting (SLM) of parts, which is related to addition of part supports. Therefore, it is necessary to investigate the addition manner of part supports in the SLM process. The molding effects in the SLM of parts with different support structures are iWarping deformation often occurs during the process of selective laser melting (SLM) of parts, which is related to addition of part supports. Therefore, it is necessary to investigate the addition manner of part supports in the SLM process. The molding effects in the SLM of parts with different support structures are investigated and one found that, under the condition of same support parameters, the support sheet which is separated and non-inclined has better molding effects; the larger the height of support structure is, the stronger the warping deformation is. After the optimization of support structures, it is found that the separated and non-inclined support structure mixed with heat conduction columns can effectively reduce the warping deformation of parts. This study provides a reference basis for the molding of high precision parts by SLM..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202002 (2016)
Planning of Area-Partition Scanning Path and Its Effect on Residual Stress of SLM Molding Parts
Deng Shishi, Yang Yongqiang, Li Yang, Wang Di, Wang Anmin, and Song Changhui
In order to solve such problems as residual stress accumulated within layers being excessive, and warpage and cracks being easy to occur as a result of the long scanning line when selective laser melting is used to mold parts, one scheme of area-partition scanning is proposed. The S-shaped orthogonal layer cross scanniIn order to solve such problems as residual stress accumulated within layers being excessive, and warpage and cracks being easy to occur as a result of the long scanning line when selective laser melting is used to mold parts, one scheme of area-partition scanning is proposed. The S-shaped orthogonal layer cross scanning strategy and area-partition scanning strategy are respectively adopted to plan scanning path and the validity of the latter strategy is experimentally confirmed. The experimental results indicate that, with the area-partition scanning strategy, the tensile stress at rims of molding parts is effectively reduced, the fluctuation of residual stress at surface is weakened, and the mechanical property of molding parts is improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202003 (2016)
Experimental Analysis of Pool Behavior in Overhang Structure Fabricated by Selective Laser Melting
Liu Tingting, Zhang Changdong, Liao Wenhe, Zhang Kai, and Wu Genli
With the Z-scan and Island-scan two schemes and selective laser melting (SLM) technology, Ti6Al4V specimens with different overhang angles are fabricated, and the relationships among molten pool behavior, overhang angle and forming quality are studied. The results show that, in the forming process, the molten pool areaWith the Z-scan and Island-scan two schemes and selective laser melting (SLM) technology, Ti6Al4V specimens with different overhang angles are fabricated, and the relationships among molten pool behavior, overhang angle and forming quality are studied. The results show that, in the forming process, the molten pool area first increases sharply till arrives at a peak value, and then decreases slowly with the increment of fabrication height. Compared with that for the plane-scan scheme, the molten pool for the contour-scan scheme is more obviously instable and its area has a larger amplitude. With the decrement of overhang angle, the molten pool area becomes small and the overhang surface becomes rough. Compared with that for the Z-scan scheme, the molten pool area for the Island-scan scheme is smaller, the molten pool is more instable, and the overhang surface roughness is higher..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202004 (2016)
Electrical Signal Characteristics of Plasma in YAG Laser Welding of A304 Stainless Steels Under Different Modes
Zhao Shengbin, Yang Lijun, Liu Tong, Yang Ruixia, Pan Jiajing, and Qiu Wencong
A novel passively electrical device is proposed to detect the electrical signals of plasma in YAG laser welding of A304 stainless steels and a high-speed camera is used to observe the plasma shapes. The results indicate that the time-domain characteristics of signals are different in different welding modes. The theoreA novel passively electrical device is proposed to detect the electrical signals of plasma in YAG laser welding of A304 stainless steels and a high-speed camera is used to observe the plasma shapes. The results indicate that the time-domain characteristics of signals are different in different welding modes. The theoretical and experimental analyses of the signal characteristics under different welding modes indicate that the plasma electrical signal is influenced by the combination of the plasma effect and sheath effect; the determinant factor resulting in different electrical signal characteristics under different welding modes is whether the keyholes are formed or not..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202005 (2016)
Microstructure and Mechanical Property of Joints in Laser Welding of Stainless Steels with Nitrogen Shielding Gas
Li Zhujie, Lü Junxia, Zou Jianglin, Zhang Jianchao, and Wu Shikai
With different proportions of nitrogen-argon hybrid shielding gas, the experiment of CO2 laser welding of 2 mm thick SUS301L austenite stainless steel is conducted. The microstructure, comprehensive mechanical, and surface corrosion-resistance properties under different proportions of nitrogen shielding gases are invesWith different proportions of nitrogen-argon hybrid shielding gas, the experiment of CO2 laser welding of 2 mm thick SUS301L austenite stainless steel is conducted. The microstructure, comprehensive mechanical, and surface corrosion-resistance properties under different proportions of nitrogen shielding gases are investigated. Experimental results indicated that, under different proportions of nitrogen shielding gases, the micro-morphologies of weld joints have no obvious difference, the nitrogen contents are the same as that of steel substrate, and the phase components are all γ-austenite with combination of a small amount of δ-ferrite; the tensile strength, bend strength, and micro-hardness of weld joints are comparable with that of steel substrate; the weld joint under the shielding of Ar gas possesses the best corrosion resistance property; with the increment of nitrogen content in shielding gas, corrosion resistance of weld joint surface gradually decreases, but the corrosion rate shows a lowering trend..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202006 (2016)
Effect of Annealing Temperature on Microstructure and Mechanical Properties of Laser Deposited TA15 Titanium Alloys
Yang Guang, Wang Wendong, Qin Lanyun, Ren Yuhang, Li Changfu, and Wang Wei
TA15 titanium alloy bulk specimens are prepared from raw material of spherical powders by laser deposition manufacturing technique. The effect of annealing temperature on the tensile mechanical properties and microstructure characteristics of TA15 titanium alloys is investigated, and the fracture mechanism and α group TA15 titanium alloy bulk specimens are prepared from raw material of spherical powders by laser deposition manufacturing technique. The effect of annealing temperature on the tensile mechanical properties and microstructure characteristics of TA15 titanium alloys is investigated, and the fracture mechanism and α group deformation mechanism on both sides of grain boundary under different annealing temperatures are analyzed. The results indicate that, the α phase in alloy microstructure is in order after the annealing treatment, and the thickness of α lamellar layer does not change so much as the annealing temperature increases; the micro-hardness is affected by the amount of α phase while it does not vary much with temperature; the α group deformation mechanisms on both sides of grain boundary are different; the crack easily appears and extends in β phase; the tensile fracture mechanism along deposition direction is different from that along perpendicular direction and the former is ductile fracture but the latter is semi-cleavage-ductile fracture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202007 (2016)
Microstructure and Mechanical Property Analysis of ZL114A Aluminum Alloy Repaired by Laser Deposition
Qin Lanyun, Pang Shuang, Yang Guang, Wang Chao, and Wang Wei
The laser deposition repair technology is used to repair the tensile specimen with pre-damage and the microstructure, tensile fracture and its neighboring deformation structure are examined and analyzed by the optical microscope and scanning electric microscope. The results show that the microstructure at repaired zoneThe laser deposition repair technology is used to repair the tensile specimen with pre-damage and the microstructure, tensile fracture and its neighboring deformation structure are examined and analyzed by the optical microscope and scanning electric microscope. The results show that the microstructure at repaired zone is composed of Al dendrites and Al-Si eutectic whose Si-phase presents Coral-like morphology. The tensile strengths at room temperature of specimens with repair-ratios of 10% and 20% can reach up to 90% and 88% of the casting standard and their elongation rates are both superior to the casting standard; the fracture mechanism at substrate zone is brittle-fracture type, while that at repair zone is ductile-fracture type; the fracture mode for micro-fractures at substrate zone is transgranular, while that at repair zone is granular..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202009 (2016)
Effect of Microstructure on Hardness and Fatigue Properties of 800 MPa High Strength Steel Fiber Laser Weld Joints
Wang Xiaonan, Zheng Zhi, Zeng Panlin, Zhang Shunhu, Zhang Min, Chen Changjun, and Chen Wengang
Laser butter welding is implemented by 6 kW fiber laser on 800 MPa dual phase cold rolled steel sheet with 1.5 mm thickness. The microstructure evolution of laser welding joint, its effect on microhardness and fatigue properties are studied. The results show that the weld joint consists of weld zone (WZ), coarse-grain Laser butter welding is implemented by 6 kW fiber laser on 800 MPa dual phase cold rolled steel sheet with 1.5 mm thickness. The microstructure evolution of laser welding joint, its effect on microhardness and fatigue properties are studied. The results show that the weld joint consists of weld zone (WZ), coarse-grain heat affected zone (CGHAZ), fine-grain HAZ (FGHAZ), mixed-grain HAZ (MGHAZ) and tempering zone (TZ). The microstructure of WZ and CGHAZ are martensite, and columnar crystals morphology is retained on original austenite grains in WZ, whereas polygonal original austenite grains are observed in CGHAZ. The microstructure of FGHAZ and MGHAZ are ferrite and martensite, and finer microstructure is obtained in FGHAZ. The microstructure of TZ consists of ferrite and tempering martensite. The microhardnesses of both MGHAZ and TZ are lower than that of base metal, and they form the softening zone of the welded joint together. Tensile fracture is in the base metal because of the narrow soften zone (0.4 mm) and low microhardness drop (~6.8%). In tension-tension fatigue tests (stress ratio is 0.1), the fatigue limit of base metal and weld joints are 545 MPa and 475 MPa respectively. Fatigue fractures are not in softening zone. The fatigue crack propagates along the phase interface between ferrite and martensite in base metal. Whereas, the fatigue crack of welded joint occurs on the austenite grain boundaries or martrnsite lath in WZ, and propagates along the intersection of columnar original austenite grain boundaries in the center of WZ, which cuts off martensite lath beam to propagate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1202010 (2016)
Materials and Thin Films
Composite Light Scattering Properties Between Slightly Rough OpticalSurface and Multi-Body Particles
Gong Lei, Wu Zhensen, Ge Chengxian, Gao Ming, and Pan Yongqiang
Based on the finite difference time domain/multi-resolution time domain (FDTD/MRTD) method, composite scattering between slightly rough optical surface and buried multi-body defect particles was researched. The concept of multi-body defect particles is put forward and the composite scattering model of slightly rough opBased on the finite difference time domain/multi-resolution time domain (FDTD/MRTD) method, composite scattering between slightly rough optical surface and buried multi-body defect particles was researched. The concept of multi-body defect particles is put forward and the composite scattering model of slightly rough optical surface and buried particles is established. The computational domain is divided into MRTD method domain and FDTD method domain based on displacement interpolation principle of DB2 wavelet scale function, and the composite scattering field is deduced. Composite scattering cross sections of buried multi-body particles are discussed in detail. Results are compared with those obtained with the method of moment, and they are found to be consistent very well, thereby proving the reliability of the proposed method. The effects of incidence angle, sphere number and sphere separation distance on composite scattering are studied. The study will provide technological support for the fields of nondestructive examination, optical film, optical performance design of micro- and nano- structures etc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1203001 (2016)
Durable Silver Reflector Prepared by Magnetron Sputtering
Xu Xu, He Wenyan, Wang Changjun, Wei Ming, and Li Bincheng
The characteristics of Sub/NiCrNx/Ag/NiCrNx/SiNx/Air multilayer structure of silver reflector prepared by magnetron sputtering are studied and the influences of N2 on the spectrums of Ag thin film, dielectric protective layer and silver mirror are analyzed. The reasons to cause low reflectance of the silver films at shThe characteristics of Sub/NiCrNx/Ag/NiCrNx/SiNx/Air multilayer structure of silver reflector prepared by magnetron sputtering are studied and the influences of N2 on the spectrums of Ag thin film, dielectric protective layer and silver mirror are analyzed. The reasons to cause low reflectance of the silver films at short-wavelength region (400~500 nm) are investigated via depth profiling with X-ray photoelectron spectroscopy and transmission electron microscope. The influences of N2 proportion of Ar/N2 on the optical properties, surface topography and crystal structure of prepared single-layer silver films are investigated during sputtering deposition via spectrophotometry, scanning electron microscopy, and X-ray diffraction. Moreover, the reflectances of prepared-silver mirrors prepared by different gas flow ratios of Ar/N2 plasma are compared and the stoichiometric ratio of SiNx thin films is analyzed. Experimental results proves that, the stoichiometric ratio of SiNx thin films is ameliorated when the silver target is sputtered with the plasma of mixed argon and nitrogen. The reflectance of the prepared silver mirrors at 400 nm wavelength is improved from 71.7% to 79.3% as the N2/Ar gas flow ratio changed from 0 to 40%. Furthermore, the silver mirrors prepared by magnetron sputtering in Ar/N2 plasma present excellent corrosion resistance and environmental stability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1203002 (2016)
Characteristics of Plasma Shock Waves in Laser-Induced Film Damage
Su Junhong, Lü Ning, and Ge Jinman
Under different laser irradiation energies and positions, the pressure value and onset time of laser plasma shock waves are collected and extracted with test microphones, the propagation law of plasma shock waves in air is analyzed, and the relation function between sound pressure value of shock waves and laser irradiaUnder different laser irradiation energies and positions, the pressure value and onset time of laser plasma shock waves are collected and extracted with test microphones, the propagation law of plasma shock waves in air is analyzed, and the relation function between sound pressure value of shock waves and laser irradiation energy is fitted. The results indicate that laser plasma shock waves propagate in the forms of spherical waves and the relationship between their sound pressure values and laser irradiation energy is nonlinear and positive..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1203003 (2016)
Measurement and Metrology
Random Phase-Shifting Speckle Patterns Analysis Algorithm Based on Principle Component Analysis
Hou Yuanyuan, and Xu Jiancheng
Phase-shifting shearography interferometry needs to extract dynamic phase of the measured object after loading, so the random phase-shifting speckle patterns analysis algorithm based on principle component analysis (PCA) is proposed. By using the correlation method, the fringe patterns with random phase shifts are obtaPhase-shifting shearography interferometry needs to extract dynamic phase of the measured object after loading, so the random phase-shifting speckle patterns analysis algorithm based on principle component analysis (PCA) is proposed. By using the correlation method, the fringe patterns with random phase shifts are obtained from the speckle patterns with random phase shifts. Then the dynamic phase distributions are extracted from one set of random phase-shifting fringe patterns by PCA. Experimental results show that the obtained fringe patterns have high signal-to-noise ratio, and the extracted phases are accurate and efficient. The proposed method is non-iterative and has no strict requirement for the spatial-carrier frequency of fringe patterns, so it is suitable for dynamic shearing speckle interferometry..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1204002 (2016)
Application of Three-Dimensional Laser Scanning Technology in Measurement of Ship Displacement
Zhang Jixing, Cheng Xiaojun, and Cheng Xiaolong
Traditional methods of calculating displacement often have certain shortcomings and drawbacks such as high labor intensity and low efficiency. With the help of the 3D laser scanning technique, this paper introduces a displacement computation method based on point cloud slicing technique. The proposed method first segmeTraditional methods of calculating displacement often have certain shortcomings and drawbacks such as high labor intensity and low efficiency. With the help of the 3D laser scanning technique, this paper introduces a displacement computation method based on point cloud slicing technique. The proposed method first segments the point cloud into several point cloud slices along z-axis. The triangle-area-integration method is adopted to calculate the cross-sectional area of each slice. The displacement can be calculated through the accumulation of each slice volume. To compare the results of the proposed methods, the displacement results of corresponding heights computed by commercial software are taken as a reference. Then we calculate the relative expanding uncertainty of the measurement results. The test results indicate that the proposed method can calculate the displacement with high accuracy, thus providing the displacement calculation with a new approach..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1204003 (2016)
Interference Phase Generated Carrier Demodulation Algorithm Based on Synchronous Carrier Restoration Method
Li Shuwang, Shao Shiyong, Mei Haiping, Hao Qilong, and Rao Ruizhong
To effectively eliminate the adverse effects of carrier delay on phase generated carrier (PGC) algorithm, a method based on synchronous carrier restoration is presented to generate the fundamental and second harmonic carrier signals. With this method the carrier information is directly extracted from interferometer sigTo effectively eliminate the adverse effects of carrier delay on phase generated carrier (PGC) algorithm, a method based on synchronous carrier restoration is presented to generate the fundamental and second harmonic carrier signals. With this method the carrier information is directly extracted from interferometer signal and then the carrier signal is restored synchronously. The basic theory of synchronous carrier restoration is elaborated, and the influences of carrier phase delay are detailedly analyzed by theoritical analysis, numerical calculation and simulated demodulation. Results of the simulation and experiment show that the mixing signal is perfectly aligned with the interference signal, both of which are obtained with the synchronous carrier restoration method. Therefore, the proposed approach can guarantee PGC algorithm to realize stable and accurate demodulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1204004 (2016)
Optical Communication
High Precision Visible Light Indoor Positioning Based on Image Communication
Guan Yang, Sun Dedong, Yin Shugang, Xin Jun, Wei Ling, Zhang Hongming, and Song Jian
A high-precision indoor positioning method based on LED and image communication is proposed, which can achieve high-precision and small-disturbance indoor positioning with low cost and wide applications. The camera is used to receive the identity information added on the LED light for the absolute position of the LED. A high-precision indoor positioning method based on LED and image communication is proposed, which can achieve high-precision and small-disturbance indoor positioning with low cost and wide applications. The camera is used to receive the identity information added on the LED light for the absolute position of the LED. And then, the absolute position of the camera can be calculated combined with data of the attitude sensor on the receiver. Results of the test experiment based on the method show that the positioning accuracy can be achieved within centimeter scale, and the receiver can be placed on most intelligent terminals just by software..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1206001 (2016)
Node Security-Aware Spectrum Allocation Algorithm in Elastic Optical Networks
Xuan Hejun, Wang Yuping, Xu Zhanqi, and Hao Shanshan
Routing and spectrum allocation for connection requests in elastic optical networks are investigated. Considering the influence of physical nodes on the security, a global constrained optimization model is established, which is with the requirement of meeting the minimum security level as the constraint and with the maRouting and spectrum allocation for connection requests in elastic optical networks are investigated. Considering the influence of physical nodes on the security, a global constrained optimization model is established, which is with the requirement of meeting the minimum security level as the constraint and with the maximum sequence number of frequency slots in networks as the optimization goal. In order to solve the constrained optimization model effectively, a global optimization algorithm is presented. The connection requests groomed are sorted according to a specific sorting policy. K paths, which satisfy the minimum security level requirement, are selected for every connection request. To minimize the maximum sequence number of frequency slots, the improved genetic algorithm is employed to determine the optimal routing and spectrum allocation scheme. In order to verify the validity of the proposed algorithm, simulations are conducted in different network topologies, and the results show that the efficient spectrum allocation can be achieved by the proposed algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1206002 (2016)
Performance Analysis and Simulation of Maximum Ratio Combining in Underwater Laser Communication
Hu Siqi, Zhou Tianhua, and Chen Weibiao
Due to the influence of absorption and scattering of seawater, the amplitude of received signal reduces and the signal-to-noise ratio (SNR) reduces during long distance underwater communications, which leads to the bit error rate (BER) of underwater laser communication systems rise, and eventually limits the distance oDue to the influence of absorption and scattering of seawater, the amplitude of received signal reduces and the signal-to-noise ratio (SNR) reduces during long distance underwater communications, which leads to the bit error rate (BER) of underwater laser communication systems rise, and eventually limits the distance of communication. For this reason, the maximum ratio combining (MRC) diversity reception technology applied in the underwater laser communication system is put forward. The improvement of MRC spatial diversity reception technology compared with the equal gain combining (EGC) spatial diversity reception technology is analyzed under the influence of absorption and scattering of water. Weighting coefficient distribution of MRC is deduced. The relationship between receiver number and system BER performance is analyzed. Monte Carlo method is used to simulate the performance improvement of MRC based on 532 nm laser at transmission distance of 100 m in Jerlov IB water with six receivers. In the IB and II type water, the relationship between BER and transmission distance is given for MRC and EGC. The theoretical analysis and simulation results show that MRC can distribute gain coefficients more reasonably according to SNR in each receiving branch, to achieve the optimal SNR. Under the requirement of same BER, MRC can realize the longest transmission distance of underwater laser communication. Under the requirement of same transmission distance, MRC can reduce BER of communication system. An engineering solution for long distance underwater laser communication system is provided..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1206003 (2016)
Feature Analysis of Aeronautical Laser Communication System and Airborne Laser Communication Experiment
Song Yansong, Chang Shuai, Tong Shoufeng, Zhang Lizhong, Jiang Huilin, Dong Yan, Dong Keyan, Zhao Xin, and Zhang Lei
Aviation platform is the critical node of the space-air-ground integration stereo-space network. The establishment of space-to-air, space-to-space and space-to-ground laser communication links is the key to achieving airborne laser communication. The composition and working principle of the airborne laser communicationAviation platform is the critical node of the space-air-ground integration stereo-space network. The establishment of space-to-air, space-to-space and space-to-ground laser communication links is the key to achieving airborne laser communication. The composition and working principle of the airborne laser communication experimental system are introduced. The particularity analysises for the airborne laser communication are carried out, including the influence of the atmospheric boundary layer, substantially random perturbation, platform high-frequency vibration, atmospheric channel and other external constraint environments on the performance of the airborne laser communication system, and the related suppression technologies are studied. The experimental results of the space-to-ground laser communication between airship and ship, the space-to-space rapid capture between helicopters and the space-to-space remote laser communication between fixed wing airships are introduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1206004 (2016)
Rapid Communications
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1215001 (2016)
Reviews
Multimodality Intravascular Imaging Technologies Based on Optical System
Li Jiawen, and Chen Zhongping
The majority of acute coronary events are caused by ruptures of vulnerable atherosclerotic plaques. Accurate identification of vulnerable plaques holds great promise in optimizing treatment plans and preventing cardiac deaths in future. However, clinically available imaging technologies are not sufficient to accuratelyThe majority of acute coronary events are caused by ruptures of vulnerable atherosclerotic plaques. Accurate identification of vulnerable plaques holds great promise in optimizing treatment plans and preventing cardiac deaths in future. However, clinically available imaging technologies are not sufficient to accurately diagnose vulnerable plaques. By the combined use of complementary imaging technologies, multimodality intravascular imaging technologies can image and quantify atherosclerotic plaques, and accurately identify vulnerable plaques. In this paper, we review the development process and the technical difficulty of multimodality intravascular imaging technologies, including intravascular ultrasound-optical coherence tomography, optical coherence tomography imaging-fluorescence, optical coherence tomography-spectrometer, intravascular photoacoustic-ultrasound and optical coherence tomography-optical coherence elastography multimodality imaging technologies. The paper will conclude with future directions of multimodality intravascular imaging technologies..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1200001 (2016)
Remote Sensing and Sensors
High-Precision Polarizing Beam Splitting System Based on Polarizing Beam Splitter
Luo Jing, Liu Dong, Xu Peituo, Bai Jian, Liu Chong, Wang Kaiwei, Yang Yongying, Tang Peijun, Cheng Zhongtao, and Liu Yanyang
The poor extinction ratio and polarization cross talk of a general polarizing beam splitter (PBS) promote us to propose a high-precision polarizing beam splitting system, which consists of a PBS and polarizers. The additional polarizers are insert into reflection channel and transmission channel of the PBS, and the traThe poor extinction ratio and polarization cross talk of a general polarizing beam splitter (PBS) promote us to propose a high-precision polarizing beam splitting system, which consists of a PBS and polarizers. The additional polarizers are insert into reflection channel and transmission channel of the PBS, and the transmission axis direction of polarizer is adjusted, which can minimize the polarization cross talk. Both the theoretical calculation and numerical simulation demonstrate that this polarizing beam splitting system can achieve polarization splitting with higher accuracy. The experimental results show that when the intensity ratio of incident light is -47.5 dB, the polarizing beam splitting error caused by a general PBS is 57.3%, while it is 14.3% after adding polarizer. When the intensity ratio of incident light is 47.8 dB, the polarizing beam splitting error caused by a general PBS is 15.5%, while it is 8.6% after adding polarizer. The proposed polarizing beam splitter system is simple and practical, which can be employed in many polarized optical systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1210001 (2016)
Refractive Index and Curvature Insensitive PbS Fiber Temperature Sensor Based on Inter-modal Interference Principle
Fu Xinghu, Yang Chuanqing, Wang Siwen, Wen Jianxiang, Dong Yanhua, Fu Guangwei, and Bi Weihong
A refractive index and curvature insensitive temperature sensor based on PbS fiber is proposed. It is simple in fabrication just by splicing a section of PbS fiber between two single mode fibers without dislocation. Due to the special refractive index distribution of the PbS fiber core, the light can be stimulated to dA refractive index and curvature insensitive temperature sensor based on PbS fiber is proposed. It is simple in fabrication just by splicing a section of PbS fiber between two single mode fibers without dislocation. Due to the special refractive index distribution of the PbS fiber core, the light can be stimulated to different modes in the core when it couples into the PbS fiber from the input single mode fiber. Different modes interfere when they couple into the output single mode fiber. The optical path differences between different modes of the PbS fiber change when the ambient temperature changes. Finally, the transmission spectrum of the sensor has a variation. Monitoring the variation of the transmission spectrum can measure the ambient temperature. Through the experiments, it is found that a complete periodic interference spectrum can be obtained when the length of PbS fiber is 4 mm. The sensing performances of temperature, refractive index and curvature of the sensor are tested, respectively. The results show that the temperature sensitivity of the sensor is 55.45 pm/℃, the refractive index sensitivity is only 2.08 nm/RIU and the curvature sensitivity is only -0.29 nm/m-1, in which RIU is refractive index unit. It means that the sensor is insensitive to refractive index and curvature. So the temperature sensor can avoid the impact of the refractive index and the curvature. The sensor has a small structure size, and it can be well used in biochemistry, industrial production and other temperature measurement occasions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1210002 (2016)
An Optical Fiber Hydrophone Used to Detect Noise in Transformer
Gao Kan, Wu Bingyan, Zhang Guilin, Lou Jin, Yang Hui, Mo Juan, and Ma Yuchao
Because of the existence of the Faraday rotator mirror，the sensing signal in the optical fiber hydrophone based on Michelson interferometric optical path is disturbed by the strong electromagnetic field. The improved sensing optical path structure separates the Faraday rotator mirror from the optical fiber hydrophone, Because of the existence of the Faraday rotator mirror，the sensing signal in the optical fiber hydrophone based on Michelson interferometric optical path is disturbed by the strong electromagnetic field. The improved sensing optical path structure separates the Faraday rotator mirror from the optical fiber hydrophone, and the sensing signal can be resistant to the strong electromagnetic field. A new type of optical fiber hydrophone is made. The optical fiber hydrophone which is installed in a large transformer can detect noise inside the transformer under different load currents successfully..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1210003 (2016)
Spectroscopy
Origins of Nephrite by Laser-Induced Breakdown Spectroscopy Using Partial Least Squares Discriminant Analysis
Wang Yajun, Yuan Xinqiang, Shi Bin, Zhang Qian, and Chen Tao
Identifying the origins of nephrite from three different places has been studied, using laser-induced breakdown spectroscopy (LIBS) coupled with partial least squares discriminant analysis (PLS-DA) approach. 146 nephrite specimens from Xinjiang (Hotan, Yutian, Qiemo), Qinghai (Golmud) and Russia (Baikal) were selected Identifying the origins of nephrite from three different places has been studied, using laser-induced breakdown spectroscopy (LIBS) coupled with partial least squares discriminant analysis (PLS-DA) approach. 146 nephrite specimens from Xinjiang (Hotan, Yutian, Qiemo), Qinghai (Golmud) and Russia (Baikal) were selected as research subjects. 111 of the specimens were chosen as calibration samples to build the PLS-DA model, and the rest 35 specimens were used as prediction samples to test the PLS-DA model. In this study, LIBS was used to test and analyze the element composition of nephrite specimens. Na, K, Al, Li, Be, Mn, Sr, Zr, Ba, Y and Ce were chosen as analysis object elements, and their spectral lines at 589.995, 766.490, 396.152, 670.793, 313.042, 257.610, 407.771, 389.138, 455.403, 437.493, 401.239 nm were selected as analysis spectral lines. The LIBS spectrum of Si at 288.158 nm was chosen as internal spectral line. Ratio between the intensity of analysis spectral lines Rx and the intensity of analysis internal spectral line was calculated. The matrix of independent variables composed by Rx was applied to calibrate and test the PLS-DA mode. This study shows that for discrimination mode built by PLS-DA approach coupled with LIBS, the correlations between category variables of calibration or prediction and the measured category variables are all remarkable with a correlation coefficient over 0.9, and low root mean squared error of cross calibration and root mean square error of prediction (less than 0.29). The discrimination accuracy for the nephrite from three different origins is 92% by PLS-DA model based on the validation set of samples. The results indicate that using LIBS coupled with PLS-DA approach can achieve a well recognition of the origins of nephrite specimens..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 12, 1211001 (2016)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20