Journals >Chinese Journal of Lasers
Contents
2008
Volume: 35 Issue 8
30 Article(s)
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Research Article
Thermal Relaxation Time of Crystal in Pulsed Laser Diode End-Pumped Solid-State Laser
Song Xiaolu, Guo Zhen, Li Bingbin, Wang Shiyu, Cai Defang, and Wen Jianguo
The process of transient thermal effect exists in pulsed laser diode (LD) end pumped solid state laser, which means that temperature distribution in laser crystal is changing with time. The process of time-varying temperature is influenced by thermal relaxation time. Based on the heat conduction equation, the characterThe process of transient thermal effect exists in pulsed laser diode (LD) end pumped solid state laser, which means that temperature distribution in laser crystal is changing with time. The process of time-varying temperature is influenced by thermal relaxation time. Based on the heat conduction equation, the characteristic of time-varying temperature in temperature declining process is calculated by analysis and numerical method. Based on the finite element method, the thermal relaxation time and its influencing factors are presented. The diameter, thermal parameters of crystal such as density, coefficient of heat conduction and specific heat are analyzed. Based on the theory of flow and heat transfer of water, influences of crystal temperature distribution such as temperature and velocity of cooling water are considered. The results show that thermal relaxation time can be controlled by changing diameter or cooling system. Based on the solution of ANSYS, time-varying temperature distribution, temperature difference and relative optical path difference between center and edge in pumped surface of crystal are analyzed. Focal length difference at different radii of the thermal lens is analyzed simply. The results indicate that in cooling process, temperature difference and relative optical path difference between center and other different radial positions are all changed with time; focus property of crystal thermal lens is also changed with time..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1132 (2008)
Evaluating Specifications on Coupled Pump Distribution in Laser Diode Array End-Pumped Large-Aperture Amplifiers
Deng Qinghua, Peng Hansheng, Ding Lei, Li Mingzhong, Wang Jianjun, Tang Jun, Luo Yiming, Lin Honghuan, Zhang Rui, and Lu Zhenhua
In laser diode array (LDA) end-pumped large-aperture amplifiers, coupling system with high efficiency and uniform pump distribution is very important. To evaluate different coupling systems, a set of evaluating specifications is put forward, including depositing efficiency, mean pump intensity, modulation, fluctuation In laser diode array (LDA) end-pumped large-aperture amplifiers, coupling system with high efficiency and uniform pump distribution is very important. To evaluate different coupling systems, a set of evaluating specifications is put forward, including depositing efficiency, mean pump intensity, modulation, fluctuation root-mean-square (RMS) and size of uniformly pumped region. In these specifications, depositing efficiency, mean pump intensity and fluctuation RMS are statistical variables, and modulation is extreme variable. Dimension index of uniformly pumped region under certain conditions is obtained based on the statistical variable fluctuation RMS. A new method of calculating these values is put forward. The variation curves of these indices are obtained through calculating the pumping area gradually. When the analyzed region is as large as the whole pumping region, varying trends of these specifications can be given out. Using these trends, different coupling methods can be compared. Calculating example of there different pumping fields shows that this set of specifications is comprehensive and is valuable to assess different coupling systems..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1139 (2008)
Direct Current and 1/f Noise Characteristics of InGaAsP/GaAs High Power Quantum Well Laser Diodes
Zhang Shuang, Guo Shuxu, Gao Fengli, Guo Xin, Cao Junsheng, and Yu Siyao
The direct current (DC) and 1/f noise property at low bias current and low frequency were investigated on the high power InGaAsP/GaAs quantum well (QW) laser diodes. By using DC test, we found that V-I and IdV/dI-I are indicators of current leakage. By using low frequency noise (LFN) test, we found that voltage noise aThe direct current (DC) and 1/f noise property at low bias current and low frequency were investigated on the high power InGaAsP/GaAs quantum well (QW) laser diodes. By using DC test, we found that V-I and IdV/dI-I are indicators of current leakage. By using low frequency noise (LFN) test, we found that voltage noise amplitude BV ∝IβV. Theoretical analysis and aging tests indicate that current index βV is correlated with the carrier transport and current leakage mechanisms. The small βV indicates that the lasers are unreliability devices with serious current leakage and non-radiative recombination..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1144 (2008)
Laser Reflection Characteristics of Cat Eye Effect of Cassegrain Lens
Zhao Yanzhong, Song Fenghua, Sun Huayan, Zhang Xi, Guo Huichao, and Xu Jiawen
Cassegrain and similar Cassegrain optical lenses are widely used in photoelectric equipment. In order to study the special laser reflection characteristics of cat eye effect of photoelectric equipment with Cassegrain optical lens, reflection model of Cassegrain lens is established using the ZEMAX software. By the methoCassegrain and similar Cassegrain optical lenses are widely used in photoelectric equipment. In order to study the special laser reflection characteristics of cat eye effect of photoelectric equipment with Cassegrain optical lens, reflection model of Cassegrain lens is established using the ZEMAX software. By the method of physical optics propagation, the reflection characteristics of cat eye effect are simulated and analyzed, and the range of incidence angle in which cat eye effect could be detected is obtained. In the experiment, a Cassegrain lens is irradiated by laser, the images of cat eye effect reflection light are obtained,and the absolute reflectivity of cat eye effect and the divergence angle of the reflection light are tested. The results show that the reflection light of cat eye effect can be detected when the expanding system is placed in the field-view of the Cassegrain lens. The center shelter leads to the decrease of the center energy at the return place. The absolute reflectivity of cat eye effect is 11.48%, the divergence angle of the reflection light is 3.3 mrad, so a detection with distance of 30 km can be easily achieved..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1149 (2008)
Emitting Complex Wavefronts by Refractive Micro-Optics Structures
Zhang Xinyu, Li Jisai, Ji An, and Xie Changsheng
Through a technique mainly consisting of single mask ultraviolet (UV) photolithography, inductively coupled plasma (ICP) etching and KOH∶H2O chemical etching, refractive microoptics structure array of 5×5 over silicon wafer is fabricated. The fine patterns fabricated over silicon substrate are transferred into nicThrough a technique mainly consisting of single mask ultraviolet (UV) photolithography, inductively coupled plasma (ICP) etching and KOH∶H2O chemical etching, refractive microoptics structure array of 5×5 over silicon wafer is fabricated. The fine patterns fabricated over silicon substrate are transferred into nickel mask by electrochemical method. The fine pattern structures over nickel mask are further copied into plastic materials by embossing operation. Photomask is composed of a large number of microholes with typical structural size in micrometer order, which are distributed by the algorithm. The surface profile characteristics of the fabricated refractive micro-optics structures are obtained by surface measurements. Through common optical measurement, emitted complex wavefronts are discussed and analyzed..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1156 (2008)
Diffraction Gratings Ablated on LiNbO3 Crystal by Femtosecond Laser Pulses
Yu Benhai, Li Yuhua, Dai Nengli, Zheng Qiguang, and Lu Peixiang
Surface diffraction gratings are written on LiNbO3 crystal by femtosecond laser pulses with the wavelength of 800 nm, pulse duration of 50 fs and repetition frequency of 1000 Hz. The diffraction efficiencies of the gratings ablated with various parameters are measured by He-Ne laser with the wavelength of 632.8 nm. TheSurface diffraction gratings are written on LiNbO3 crystal by femtosecond laser pulses with the wavelength of 800 nm, pulse duration of 50 fs and repetition frequency of 1000 Hz. The diffraction efficiencies of the gratings ablated with various parameters are measured by He-Ne laser with the wavelength of 632.8 nm. The 1-order diffraction efficiencies of the gratings improve from 1.7% to 2.3% with the increase of ablation speed from 20 μm/s to 200 μm/s, and decrease from 1.9% to 1.3% with the increase of pulse energy from 70 nJ to 110 nJ, respectively. The experimental and theoretical results show that the diffraction efficiencies of gratings can be improved by increasing ablation speed and grating constant or decreasing pulse energy..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1161 (2008)
Technical Optimization of Multi-Level Diffractive Optical Elements
Liu Qiang, Wu Rong, Zhang Xiaobo, Li Yongping, and Tian Yangchao
From the error analysis of multi-level diffractive optical elements (MDOE) in etching process, the parameter of error skewness was suggested to reflect the overall etching error. The variation of error skewness versus the beam shaping effect of diffractive optical elements is investigated, and a flat interval which canFrom the error analysis of multi-level diffractive optical elements (MDOE) in etching process, the parameter of error skewness was suggested to reflect the overall etching error. The variation of error skewness versus the beam shaping effect of diffractive optical elements is investigated, and a flat interval which can reduce the impact of etching error existed in the curve of error skewness. According to these curves, a technical method for improving the factual illumination quality of MDOE was proposed by controlling etching depth. The experimental results show that the peak value (PV) of the optical field parameter reduces about 30% after the technical optimization..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1165 (2008)
Application of Raman Spectrum in Water Quality Analysis
Yang Changhu, Zeng Xiaoying, Yuan Jianhui, and Liao Jiaxin
Laser Raman spectrum method was used to study hardness index of tap water sample in different stages of waterworks production. Ratio between the bending vibration peak intensity and stretching vibration peak intensity of water samples was measured. Depolarization ratio of laser Raman spectrum at stretching vibration waLaser Raman spectrum method was used to study hardness index of tap water sample in different stages of waterworks production. Ratio between the bending vibration peak intensity and stretching vibration peak intensity of water samples was measured. Depolarization ratio of laser Raman spectrum at stretching vibration was also calculated. The results show that ratio between the bending vibration intensity and stretching vibration intensity of water samples decreases with the decrease of the samples’ total hardness, and depolarization ratio of laser Raman spectrum at stretching vibration decreases too..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1169 (2008)
High Repetition Rate, Short Pulse-Width All-Solid-State Laser Seed for Fiber Amplifier
Feng Yutong, Meng Junqing, Bi Jinzi, Du Songtao, Zhou Jun, and Chen Weibiao
Cascaded fiber amplifier with high repetition rate, short pulse-width all-solid-state laser seed can achieve high output power. The average output power that is close to continuous wave (CW) performance is easily achieved for CW-pumped, high-repetitively Q-switched Nd∶YVO4 laser. The major factors influencing the pulseCascaded fiber amplifier with high repetition rate, short pulse-width all-solid-state laser seed can achieve high output power. The average output power that is close to continuous wave (CW) performance is easily achieved for CW-pumped, high-repetitively Q-switched Nd∶YVO4 laser. The major factors influencing the pulse energy and pulse-width in acousto-optic (AO) Q-switched laser are analyzed, and the resonance parameters are optimized. The Nd∶YVO4 laser end-pumped by a fiber-coupled laser diode (LD) is reported, and A-O Q-switched 1064 nm laser with repetition rate larger than 100 kHz and pulse-width shorter than 20 ns is achieved. At the pump power of 5.7 W, laser seed with pulse width of 15.3 ns and pulse repetition rate of 150 kHz is acquired. The final output power of 20 W is achieved with the fiber amplifier..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1173 (2008)
All Fiber Single-Mode Q-Switched Ytterbium-Doped Fiber Laser Based on PLZT Switch
Xu Dangpeng, Li Mingzhong, Wang Jianjun, Zhang Rui, Lin Honghuan, Che Yaliang, and Lu Zhenhua
PLZT electro-optic (EO) ceramic has good transparency and high EO effect. It has many advantages for realizing the all-fiber Q-switch. The principle of Q-switch based on PLZT was analyzed. And the time distribution of the Q-switch was measured. An all fiber single-mode actively Q-switched ytterbium-doped ring fiber lasPLZT electro-optic (EO) ceramic has good transparency and high EO effect. It has many advantages for realizing the all-fiber Q-switch. The principle of Q-switch based on PLZT was analyzed. And the time distribution of the Q-switch was measured. An all fiber single-mode actively Q-switched ytterbium-doped ring fiber laser based on PLZT switch was studied in experiment. The peak power, pulse width, spectral width and pulse energy of the Q-switched pulse are 25.6 W, 80 ns, 1 nm and 2.0 μJ respectively. At the same time, the effect of the pump power and repetition rate on pulse width and peak power was presented. The results show that the peak power of the pulse increases with the pump power and the pulse width decreases at the same repetition rate, and the pulse width increases with the repetition rate and the peak power decreases at the same pump power..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1177 (2008)
Amplified Spontaneous Emission Injection Wavelength-Locked Fabry-Perot Laser Diodes
Meng Hongyun, and Lee ChangHee
The wavelength-division-multiplexing passive optical network (WDM-PON) has been considered as a promising solution for future broadband access networks. The WDM-PON based on the amplified spontaneous emission (ASE) injected wavelength-locked Fabry-Perot (F-P) laser diodes has gained great attention because of its cost-The wavelength-division-multiplexing passive optical network (WDM-PON) has been considered as a promising solution for future broadband access networks. The WDM-PON based on the amplified spontaneous emission (ASE) injected wavelength-locked Fabry-Perot (F-P) laser diodes has gained great attention because of its cost-effectiveness and color-free operation. The gain, side-mode suppression ratio (SMSR) and relative intensity noise (RIN) of the wavelength-locked F-P laser diode (LD) have been studied experimentally. And the relationship between injection current and the reflectivity of front facet of F-P LD, for a given ASE and gain, has been studied theoretically and experimentally. The best RIN and SMSR can be got with the injection current which is 1.3～1.7 times of threshold current. And there is an optimum front facet for a given ASE injection power and gain with the smallest injection current..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1181 (2008)
Characteristic of Compound Two-Ring Combined Rayleigh Backscattering Fiber Optic Rotation Sensing
[in Chinese], and [in Chinese]
A novel compound two-ring combined Rayleigh backscattering fiber optic rotation sensor (RBFORS) is demonstrated and simulated based on the working principle given by A. Kung. The theoretical model of the two-ring resonators combined RBFORS is established by using two 2×2 fiber star couplers. The output signal charA novel compound two-ring combined Rayleigh backscattering fiber optic rotation sensor (RBFORS) is demonstrated and simulated based on the working principle given by A. Kung. The theoretical model of the two-ring resonators combined RBFORS is established by using two 2×2 fiber star couplers. The output signal characteristics of optical time domain reflectometer (OTDR) are deduced and analyzed by optimizing the structure parameters of the two rings cavity lengths and coupling ratios. The experiment system is constructed by the two-ring with the lengthes of L1=1500 m and L2=1078 m and fiber couplers with the coupling ratios of k1=95.23% and k2=94.88%, respectively. The Rayleigh backscattering signals are measured at different rotation rates. The experimental results are agreement with the theoretical prediction. The measurement intensity is increased by utilizing the compound two-ring structure. Therefore, the valid data number is increased, which is helpful to identify and enhance the precision of the measurement rotation rate..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1208 (2008)
Pressure Optical Fiber Vector Hydrophone Made of Thin-Walled Cylindrical Shell
Kang Chong, Zhang Min, Chen Hongjuan, Pang Meng, Lü Wenlei, and Qin Yanfang
The basic principle of pressure optical fiber vector hydrophone made of thin-walled cylindrical shell is described. The Michelson interferometer is used to measure the acoustic pressure signal. The Jones matrix theory is used to analyze the reasons for the decline of polarization of interference, and the decline of polThe basic principle of pressure optical fiber vector hydrophone made of thin-walled cylindrical shell is described. The Michelson interferometer is used to measure the acoustic pressure signal. The Jones matrix theory is used to analyze the reasons for the decline of polarization of interference, and the decline of polarization is compensated by Faraday mirror. This optical fiber vector hydrophone adopts the basic acoustic theory of the pressure sentence direction, and other cosine point tropism curves are simulated by computer. The theory of axisymmetric problems of quasi-static mechanics have been used to analyze back-lining structure model of the fiber optic vector hydrophone, to calculate sensitivity of acoustic pressure differential phase shift, and to obtain analytical expression. The pressure optical fiber vector hydrophone made of thin-walled cylindrical shell is designed by experiment based on the fiber optic Michelson interferometer principle. The experimental measurement of the sensitivity of optical phase agrees well with the results for theoretical analysis. The point tropism measurement is basically consistent with the simulation analysis. This provides reference for the development of the high sensitivity for the small size of vector optical fiber hydrophone..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1214 (2008)
Oxygen Sensor Based on U-shaped Plastic Optical Fiber
Chu Fenghong, Cai Haiwen, Qu Ronghui, and Fang Zujie
A oxygen sensor based on fluorescence quenching is reported, plastic optical fiber as sensor head and light transmit element for oxygen sensor are adopted. The sensor head is made into U shape. We use Dichlorotris (1,10-phenanthroline) ruthenium (Ⅱ) as fluorescence indictor. Sol-gel method is used to prepare the sensorA oxygen sensor based on fluorescence quenching is reported, plastic optical fiber as sensor head and light transmit element for oxygen sensor are adopted. The sensor head is made into U shape. We use Dichlorotris (1,10-phenanthroline) ruthenium (Ⅱ) as fluorescence indictor. Sol-gel method is used to prepare the sensor material. We detect the fluorescence lifetime by using phase modulation technique. The effect of bending radius on sensitivity is measured, and we find that the system sensitivity will increase when the curve radius decrease. We also measure the relationship between oxygen concentration and fluorescence lifetime, and find that they are sub-linearity. Double fluorescence site model is put forward to explain this phenomenon..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1220 (2008)
Laser Manufacturing
Theoretical Analysis and Numerical Simulation of Laser to Rock
Li Mi, Wang Yanlou, Wang Yali, Zhang Chuanxu, and Liu Jun
The technology of laser drilling rock has wide applied future in petroleum industry, but there are few mechanism researches of laser to rock interiorly. This thesis analyzed the temperature distribution of the sandstone under the laser with uniform and Gaussian intensity according to the instability heat transfer theorThe technology of laser drilling rock has wide applied future in petroleum industry, but there are few mechanism researches of laser to rock interiorly. This thesis analyzed the temperature distribution of the sandstone under the laser with uniform and Gaussian intensity according to the instability heat transfer theory, then simulated the heat stress distribution and the minimum laser intensity to drill sandstone according to the stress equation and boundary condition. The fusion and gasification model was constructed according to the law of conservation of energy and the fusion and gasification speed at certain laser power was calculated. The simulation results show that the speed of laser drilling rock is much faster than mechanical revolving aiguilles technology in deep oil well and has prominent industrial application potential..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1245 (2008)
Dynamic Characteristic Analysis of Impinging Jet in Laser Drilling
Hu Jun, Guo Shaogang, Luo Lei, and Yao Zhenqiang
The interaction of an impinging jet in laser drilling is carried out using an explicit, coupled solution algorithm with solution-based mesh adaptation. The essential process of gas jet-workpiece interaction can be described through the description of axisymmetrical impinging jet. It is completely shown that there are tThe interaction of an impinging jet in laser drilling is carried out using an explicit, coupled solution algorithm with solution-based mesh adaptation. The essential process of gas jet-workpiece interaction can be described through the description of axisymmetrical impinging jet. It is completely shown that there are two states including contact and separation between the incident shock and the normal shock in gas jet-workpiece interaction. At the same time, this paper shows the reason for the existence of the second reasonable ranges of laser cutting. The effect of processing parameter on dynamic characteristic is analyzed, and this paper also analyzes the relationship between machining capacity of assist gas and standoff distance. The mass flow rate decreases rapidly with the increase of standoff distance before the end of direct interaction between the incident shock and the normal shock, so the standoff distance should be set in reasonable ranges..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1250 (2008)
Numerical Model and Simulation for Laser-Intensified Surface Nitriding
Cao Liqin, Xuan Fuzhen, Wang Zhengdong, and Tu Shandong
Finite-element models of the temperature coupled the concentration of kinetics during laser nitriding were considered. Coupled calculations of the non-steady state Fourier heat conduction equation and the Fick law of modified diffusion equation showed the variation and distribution of nitrogen concentration and the temFinite-element models of the temperature coupled the concentration of kinetics during laser nitriding were considered. Coupled calculations of the non-steady state Fourier heat conduction equation and the Fick law of modified diffusion equation showed the variation and distribution of nitrogen concentration and the temperature in the metal surface layer. The results indicate that, the temperature of laser nitriding can be controlled exactly to gain the critical values of the heat flux and scanning rate respectively by trial-and-error, as the applicable reference range of progress. The modified diffusion equation, which considered the temperature gradient and thus showed a fairly good explanation of the N diffusion using the high-energy laser to fill the heat. The whole thickness of nitrides layer can be obtained through the simulation. The dynamic of laser nitriding is the high surface temperature gradient, which differs from the conventional process. The nitrogen concentration gradient is never considered as the main influence element. The thickness of nitrides increases when heat flux is increased or the scanning rate is reduced. Simulation indicates that good results can be obtained when these parameters are chosen properly..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1255 (2008)
Effect of V-N Alloy on Microstructure and Wear Resistance of Co-Based Alloy Laser Coating
Li Mingxi, Zhao Qingyu, and He Yizhu
Co-based alloy coatings with and without V-N alloy addition were cladded on the surface of the low carbon steel (SPHC). The microstructure and phases of the coatings were studied with optical microscope (OP), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction instrument (XRCo-based alloy coatings with and without V-N alloy addition were cladded on the surface of the low carbon steel (SPHC). The microstructure and phases of the coatings were studied with optical microscope (OP), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction instrument (XRD). The microhardness and sliding wear resistance of the coatings were also tested. The results show that γ-Co and Cr23C6 exists in Co-based alloy coatings. Fine microstructure and other phases, such as σ-FeV and VN are obtained with V-N alloy addition. The microhardness is improved and higher at interface than that near the top surface. With the increase of laser scanning speed, the wear resistance of the coatings is improved by adding V-N alloy. The abrasive mechanism of the coating is also analyzed..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1260 (2008)
Numerical Study on the Laser Bending of Stainless Steel Foil with Pre-Stresses
Liu Jie, Sun Sheng, and Guan Yanjin
Through using a new laser bending process, the distribution of expected pre-stress was obtained on the heated zone of AISI 304 steel foil with thickness of 0.1 mm by applying initial displacement to the sample’s free end. Considering the characteristics of laser bending, three-dimensional (3D) thermomechanical finite eThrough using a new laser bending process, the distribution of expected pre-stress was obtained on the heated zone of AISI 304 steel foil with thickness of 0.1 mm by applying initial displacement to the sample’s free end. Considering the characteristics of laser bending, three-dimensional (3D) thermomechanical finite element method (FEM) models of laser bending process with various pre-stresses were developed based on the buckling mechanism (BM). Through comparing the simulation results of different models, the mechanism of laser bending with pre-stresses was explained. The simulation results show that the deformation of the stainless steel foil under buckling mechanism depends on the integration of the thermal stress and the pre-stress when the laser beam irradiates the foil. The forming performance can be improved significantly under pre-stress, and the deformation direction can also be controlled easily by changing the direction and value of the pre-loading. The bending angles of the steel foils increase remarkably with the increase of the pre-loading, and both are almost in linear relationship..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1265 (2008)
High Wear-Resistant Particulate Reinforced Composite Coatings for Corrugated Rollers by Laser Cladding
Qian Zhaoyong, Zhong Minlin, Liu Wenjin, Ma Mingxing, and Zhang Hongjun
The present hardening technologies for corrugated rollers, such as intermediate frequency quenching, nitrogen hardening, chromeplate, laser transformation hardening and tungsten carbide spraying, have some limitation on cost, lifetime, technique stability and rejuvenation capability. Laser cladding offers an approach tThe present hardening technologies for corrugated rollers, such as intermediate frequency quenching, nitrogen hardening, chromeplate, laser transformation hardening and tungsten carbide spraying, have some limitation on cost, lifetime, technique stability and rejuvenation capability. Laser cladding offers an approach to improve the above comprehensive properties when hardfacing and repairing the corrugated rollers. This paper reported a laser cladded particulate reinforced composite coating by using a unique cladding powder material THW-64 to tackle the severe dry friction abrasive wear on corrugated roller surface. After laser cladding with optimized parameters, the crack-free coatings with thickness over 0.4 mm, have strong metallurgic bond with the substrate. The main microstructure of the coating consists of hypoeutectic matrix and many homogeneously distributed complex carbide particles with average hardness of 915HV0.2. Wear test and real production applications demonstrate that the abrasive wear resistance and working lifetime of corrugated rollers hardfaced by these particulate-reinforced composite coatings have been dramatically improved..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1271 (2008)
Sound Controlled Focus System for Laser Drilling System
Wang Meng, Liu Tiegen, Xu Baozhong, Zhang Guoshun, and Yu Donghe
Measurement and control of the laser beam focus remain to be solved as a technique for laser drilling. There have been developed many methods for laser focus control, where transducers for monitoring focus are key technologies. So the development of focus control system fitted to materials and processing schedule is veMeasurement and control of the laser beam focus remain to be solved as a technique for laser drilling. There have been developed many methods for laser focus control, where transducers for monitoring focus are key technologies. So the development of focus control system fitted to materials and processing schedule is very important. The sound transducer based laser focus control system is proposed, which uses aural sound as a control parameter, and measures and controlls laser focus in real time on line. Through testing the technology in diamond laser drilling system and comparing it with traditional laser control, we get a satisfying result..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1277 (2008)
Materials and Thin Films
Design and Fabrication of Graded Reflectivity Mirrors
Lü Guonuan, Li Dawei, Huang Jianbing, and Yi Kui
According to the parameter requirement of the graded reflectivity mirror (GRM) with Gaussian profile, the layer structure and the mask pattern were designed by using graded-thickness middle layer. The mask and the mask switchover equipment were designed considering the actual requirement of the thin films and the speciAccording to the parameter requirement of the graded reflectivity mirror (GRM) with Gaussian profile, the layer structure and the mask pattern were designed by using graded-thickness middle layer. The mask and the mask switchover equipment were designed considering the actual requirement of the thin films and the specific deposit facility. All layers of the graded reflectivity mirror were deposited in one high vacuum environment. Using a direct measuring method, the radial reflectivity distribution of graded reflectivity mirror with Gaussian profile was measured. The measuring results indicate that the graded reflectivity mirror with Gaussian profile prepared with this technique is basically in accordance with the design requirement. Analysis indicates that the mask pattern and accuracy influence the deposit result. The scattering effect of the mask on the material molecules increases with the decrease of the design dimension, the center reflectivity of the sample becomes lower than the design requirement, and the side lobe arises at the edge of the sample. The improving methods are proposed as decreasing the distance between the substrate and the mask, and increasing the monitor accuracy of the layer thickness..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1240 (2008)
Measurement and Metrology
An Approach for Calibrating Rotor Position of Three-Dimensional Measurement System for Line-Structure Light
Wu Qingyang, Li Jinzhen, Su Xianyu, and Hui Bin
To simplify the procedure of rotation axis positioning, a flexible and real-time calibration method is proposed. A plane calibration board with tessellated pattern is placed on the rotating stage, the calibration board was recorded at every point when the stage was rotated. Then the coordinates of these character pointTo simplify the procedure of rotation axis positioning, a flexible and real-time calibration method is proposed. A plane calibration board with tessellated pattern is placed on the rotating stage, the calibration board was recorded at every point when the stage was rotated. Then the coordinates of these character points on the target are calculated by processing these pictures. At last, the axis equation of the working stage is acquired by linear fitting with the circle centers which were gotten by circle fitting with the character points. This method is proved by experiment, and the root-mean-square error of a measured object is 0.04 mm..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1224 (2008)
ntropic Squeezing of the Optical Field in the Two-Photon Jaynes-Cummings Model
ERen Min, Qian Yan, Liu Zhengjun, Ma Aiqun, Kang Dongpeng, and Liu Shutian
Traditional researches on the squeezing effect of optical field are based on Heisenberg′s uncertainty principle and use root mean square (RMS) deviation to measure the quantum fluctuation of optical field. However, RMS deviation only contains the second-order statistical moments of the density operator. Thus under manyTraditional researches on the squeezing effect of optical field are based on Heisenberg′s uncertainty principle and use root mean square (RMS) deviation to measure the quantum fluctuation of optical field. However, RMS deviation only contains the second-order statistical moments of the density operator. Thus under many circumstances, RMS deviation cannot precisely measure the quantum fluctuation. In fact, Heisenberg′s uncertainty principle is a special case of entropy uncertainty relation, and entropy can be used to measure the quantum fluctuation of the quadrature components of the field. Based on entropy uncertainty relation, the concept of entropy squeezing has been formulated. Entropy squeezing of the optical field in two photon Jaynes-Cummings (J-C) model is discussed. By comparing, it is found that the entropy exponential δxf(t) is more sensitive to the squeezing effect of optical field than the RMS deviation Δxf(t), and is a high sensitive parameter to measure optical field..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1228 (2008)
Signal Processing of Displacement Interferometer Based on the Continuous Wavelet Transform
Liu Shouxian, Li Zeren, Wu Jianrong, Wang Detian, Liu Jun, and Meng Jianhua
A transient displacement interferometer signal processing method based on the continuous wavelet transform (CWT) is proposed. The interference signal is analyzed by CWT, and the frequency and the velocity of the signal can be deduced. One main characteristic of CWT is its adaptive nature for signals with large variatioA transient displacement interferometer signal processing method based on the continuous wavelet transform (CWT) is proposed. The interference signal is analyzed by CWT, and the frequency and the velocity of the signal can be deduced. One main characteristic of CWT is its adaptive nature for signals with large variations in frequency. In the flexible time window, if the varying central frequency is equal or close to the instantaneous frequency of local signals, the modulus of CWT is maximal, so the local frequency is determined. The processing results of simulated interference signals show that the relative error is less than 3%. Similarly, velocity history can be precisely recovered from signals of fiber displacement interferometer in detonation experiment..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1235 (2008)
Optical Communication
Generation of Advanced Modulation Formats Based on Mach-Zehnder Modulators
He Jing, Liu Limin, Chen Lin, and Wen Shuangchun
A novel scheme, using differential Mach-Zehnder modulator (DMZM) for generation of 80 Gbit/s return-to-zero differential phase-shift keyed (RZ-DPSK), carrier-suppressed (CS) RZ-DPSK, return-to-zero differential quadrature phase-shift keyed (RZ-DQPSK) and CSRZ-DQPSK, is proposed. To generate RZ/CSRZ-DQPSK, it needs onlyA novel scheme, using differential Mach-Zehnder modulator (DMZM) for generation of 80 Gbit/s return-to-zero differential phase-shift keyed (RZ-DPSK), carrier-suppressed (CS) RZ-DPSK, return-to-zero differential quadrature phase-shift keyed (RZ-DQPSK) and CSRZ-DQPSK, is proposed. To generate RZ/CSRZ-DQPSK, it needs only to add a dual-drive MZM based on the 80 Gbit/s RZ/CSRZ-DPSK signal which is generated by a two differential cascaded MZM. The proposed method of the generation of RZ/CSRZ-DPSK and RZ/CSRZ-DQPSK is of expansibility and simplicity. Simulation results show that CSRZ-DPSK has a more compact spectrum than that of RZ-DPSK, while the DQPSK has a similar spectral shape to that of DPSK, with its spectrum being compressed by a factor of two due to the halved symbol rate for transmission at a fixed bit rate..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1185 (2008)
Analysis of Characteristics of the Interleaver Based on a Double-Coupler Resonator
Li Weibin, and Sun Junqiang
In order to improve the transmission performance of the conventional Mach-Zehnder (MZ) interferometer, a novel interleaver based on MZ interferometer with a double-coupler and single mode fiber resonator in one arm is presented. The output expression is derived and numerical simulation is performed. The simulation indiIn order to improve the transmission performance of the conventional Mach-Zehnder (MZ) interferometer, a novel interleaver based on MZ interferometer with a double-coupler and single mode fiber resonator in one arm is presented. The output expression is derived and numerical simulation is performed. The simulation indicates that the bandwidth of 0.5 dB passband and 25 dB stopband of proposed interleaver are simultaneously improved remarkably, which are much wider than those of the conventional MZ interferometer. The filtering performance of this proposed interleaver, which achieves a nearly square spectrum response, is much better than that of the conventional MZ. Influence on its transimission characteristics by the parameters caused by double-coupler resonator, coupling ratio and length of resonator, is also discussed, and the variations ranges of the parameters are also given for the communication requirements..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1191 (2008)
Implementation of Superstructure Fiber Bragg Gratings-Orthogonal Wavelength Division Multiplexing and Analysis of Receiver Crosstalk
Li Shuo, Shou Guochu, and Hu Yihong
The characteristics of superstructure fiber Bragg gratings (SSFBG) as pulse shaping filters were illustrated. It was interpreted that SSFBG can produce regular rectangle optical pulses in time domain whose optical power spectral density in frequency domain is sinc function. When channel separation was integral times ofThe characteristics of superstructure fiber Bragg gratings (SSFBG) as pulse shaping filters were illustrated. It was interpreted that SSFBG can produce regular rectangle optical pulses in time domain whose optical power spectral density in frequency domain is sinc function. When channel separation was integral times of optical code rate, the neighbor channel presents zero point at the center frequency of signal channel, and the frequency spectrum were orthogonally overlapped. An orthogonal wavelength division multiplexing(OWDM) system based on SSFBG was presented. The system consists of SSFBG in transmitter works as pulse shaper and a narrow band filer in receiver. Mathematic models and simulation results are presented for the ideal narrow pass filter (NPF) and Gaussian filter receiver crosstalk. The simulation results show that both the ideal NPF and Gaussian filter can minimize the inter channel crosstalk. The crosstalk of receiver is weaker than channel crosstalk by about 10 dB when the filter in receiver is narrow enough. The crosstalk of ideal NPF receiver is weaker than Gaussian filter receiver by about 2～5 dB..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1195 (2008)
Additional Applications of Modified Duobinary Return-to-Zero Signal in the Label Switching Optical System
Shao Yufeng, Wen Shuangchun, Chen Lin, and Yu Jianjun
Two novel orthogonal modulation schemes, in which a modified duobinary return-to-zero (MD-RZ) signal was generated as a label for optical switching network, were proposed. In one scheme, a non-return-to-zero differential phase shift keying (NRZ-DPSK) signal was generated as a payload, while in another scheme, a non-retTwo novel orthogonal modulation schemes, in which a modified duobinary return-to-zero (MD-RZ) signal was generated as a label for optical switching network, were proposed. In one scheme, a non-return-to-zero differential phase shift keying (NRZ-DPSK) signal was generated as a payload, while in another scheme, a non-return-to-zero differential quadrature phase shift keying (NRZ-DQPSK) format payload was introduced. A simple method, in which the clock was extracted and recovered from label signals, was adopted. The spectra of two optical packet signals in the back-to-back label switching systems with 2.5 Gbit/s label and 10 Gbit/s payload, respectively, are compared. It is shown that the optical packet signal with a larger duty cycle label has higher spectral efficiency. In the back-to-back system, 2.5 Gbit/s MD-RZ labels with different duty cycles can be directly measured by a conventional binary intensity modulation direct detection (IM-DD) receiver. The MD-RZ labels of two optical packet signals can avoid the eye diagram distortion for long-distance transmission if the dispersion can be compensated. When the input power is beyond 18 dBm, the eye-opening penalty of MD-RZ label with a larger duty cycle is more robust in the label-detecting path..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1201 (2008)
Reviews
Review of Nondestructive Measurement of Fruit Quality by Means of Near Infrared Spectroscopy
Han Donghai, and Wang Jiahua
An overview of near infrared (NIR) spectroscopy for use in measuring quality attributes of horticultural produce is given. Nondestructive quality inspection and sorting technique based on NIR technique is widely used in post-harvest processing and quality control. Different spectrophotometer designs and measurement priAn overview of near infrared (NIR) spectroscopy for use in measuring quality attributes of horticultural produce is given. Nondestructive quality inspection and sorting technique based on NIR technique is widely used in post-harvest processing and quality control. Different spectrophotometer designs and measurement principles are compared, and novel techniques for the estimation of light absorption and scattering properties of fruit tissue are reviewed. Chemometrics is an essential part of NIR spectroscopy, and some available preprocessing and regression techniques, including nonlinear ones, are discussed. The effects of orchard state on spectrum, and correction method, such as temperature compensation, are addressed. Most applications of NIR spectroscopy have focused on the nondestructive measurement of soluble solids content of fruit where typically a root mean square error of prediction of Brix can be achieved, and other applications involving texture, acidity or disorders of fruit have also been reported. Finally, the application prospects of this technology were analyzed..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 8, 1123 (2008)
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