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ISSN1001-3806 CN51-1125/TN Map

2004 Vol. 28, No. 2

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Analysis of effective utility of laser power in process of powder feeding laser cladding
WANG Yong-feng, XUE Chun-fang, TIAN Xin-li, ZHOU Lan-ying
2004, 28(2): 113-115.
Abstract:
According to the analysis of the interaction of laser,powder and melting pool,a model of effective utility of laser power in process of powder feeding laser cladding is presented,and then calculation is performed with the parameters in process. It can be seen from the result that the amount of effective utility of laser power is small. The model objectively reflects the major relationship between the parameters and the results of process.It also provides a theoretical foundation for optimizing the process parameters,predicting and evaluating the quality of clad coating.
Side-pumping coupler technology for double-clad fiber
WEI Wen-lou, OU Pan, YAN Pin, GONG Ma-li, XIAO Li-min
2004, 28(2): 116-120.
Abstract:
Pumping coupler technology is one of the critical technologies for high-power fiber lasers.The side-pumping coupler technology for double-clad fiber can transfer pumping light into inner cladding through the side of the fiber.It has many advantages over end-pumping technology.There are several kinds of side-pumping structures according to the characteristics of double-clad fiber laser. In the paper,the side-pumping structures,especially which have been adopt in experiments,are introduced.Moreover the characteristics of these technologies are compared.
2004, 28(2): 120-120.
Abstract:
Design of PCs cluster system of broadband optical bus interconnection network
HUANG Ping, LUO Feng-guang, CAO Ming-cui, WANG Jiang-yi
2004, 28(2): 121-123.
Abstract:
A PCs cluster of broadband optical bus interconnect network is introduced in this paper.The broadband multiplayer free-space optical data bus and VCSEL/MSM-CMOS integrate device are used to realize the interconnection of four computers in this system.The special communication adapter is used to realize the conversion between HIPPI (high performance parallel interface) protocol and PCI (peripheral component interface) protocol.The capacity of the optical interconnection network is 60Gbit/s which is fit for high speed communication between the computers.
Design and implementation of very short reach
LU Xian, GAO Ze-hua, JI Yue-feng
2004, 28(2): 124-127.
Abstract:
Very short reach(VSR) provides a cost-effective solution for optical interconnection between routers,switches,and DWDM systems. The fundamental of VSR is analysed. The hardware implementation and related test results are presented. It shows that this scheme is feasible.
Study on optimal culturing of high proteinase-producing mucor racemosus mutated by CO2 laser
LI Jia, LIU Xin, LIU Ke-wu, GUO Jin-lin, ZHANG Yong-xia, XIAO Ge, HUANG Xin-he
2004, 28(2): 128-130.
Abstract:
Mucor racemosus 137 was isolated from fermented bean curd and brought to mutation by radiation of CO2 laser. The duration for radiation was 40s with distance of 22cm, and the diameter of laser beam was 0.4cm. High proteinase-producing mutant MR137-3 was obtained after screening cultures. The MR137-3 was found to have stable proteinase-producing activity in descendant cultures. The optimal culturing could be obtained at 30℃, pH6.0, culturing duration of 72h, with water content of 65% of culture medium.
2004, 28(2): 130-130.
Abstract:
Microcutting Si wafer in water bath by second harmonic output of YAG laser
LING Lei, LOU Qi-hong, LI Shu-zhi, YE Zheng-huan, DONG Jing-xing, WEI Yun-rong
2004, 28(2): 131-132,143.
Abstract:
The results are reported that the splashes of microcutting Si wafer by second harmonic output of YAG laser in water bath may be fewer than in air environment.The surface morphology and etching rate for water bath and air environment are compared in detail.The cutting gap as small as 50μm with edge fluctuation less than 5μm is obtained in water bath.This technology may be helpful for industrial applications.
Target recognization under different complicated background of cloud
YI Heng-yu, LÜ Bai-dai, JI Yun-song
2004, 28(2): 133-136,140.
Abstract:
How to recognize targets under complicated background of cloud is studied in this paper by stimulating optical correlation. Some factors influencing recognition are calculated, such as the change of shape of cloud, target intensity, clearness or faintness of input image and so on. Simulation results show that targets can be found more easily in cumulus or stratus than in undulance cloud, because undulance cloud is more abrupt change in its intensity. The analyses also show that the clearer the input image is, the more easily the target is recognized;and the more intensive the target is, the more easily it is recognized.
The design of beam delivery system of RF CO2 laser ceramic substrate scriber
HOU Lian-ping, CHEN Pei-feng, WANG Wei, ZHU Hong-liang
2004, 28(2): 137-140.
Abstract:
The characteristic of RF CO2 laser ceramic substrate scribing has been presented. The design principle of beam delivery system is analyzed. Function and characteristic of circular polarizer and Galileo defocusing telescopic system are particularly discussed. The beam delivery system is optimized and simulated and its optical path and imaging quality diagrams are plotted.The experimental outcome conforms to theory. Processing quality to alumina ceramic substrate by our scriber is up to that of the same kind of foreign products.
Periodically poled second harmonic green light generation in near-stoichiometric MgO-doped LiNbO3 crystal
YAO Jiang-hong, YAN Bo-xia, CHEN Ya-hui, DENG Hao-liang, CHEN Shao-lin, XU Jing-jun, ZHANG Guang-yin
2004, 28(2): 141-143.
Abstract:
LiNbO3 crystal with different MgO doped concentration were processed by vapor transport equilibration.The processed crystals doped 2%(mole fraction) MgO increased the photoreactive damage resistance by at least 4 orders of magnitude compared with congruent crystal.By applying an external electric field of 4.5kV/mm,we obtained a periodically poled domain structure with a 6.8μm period and 1.0mm thickness in the doped MgO2%(mole fraction) near-stoichioment LiNbO3 crystal.A Q-switched Nd:YAG laser was used as the fundamental beam source at 1.064μm.When input power was 230mW,the green SHG at 0.532μm was obtained with 1.22% conversion efficiency.
Propagation of flat-topped light beams passing through ABCD optical systems
ZENG Qing-gang, ZHANG Bin, CHU Xiao-liang
2004, 28(2): 144-146.
Abstract:
Making use of the new model of flat-topped light beams proposed by LI recently,the analytical expression of the field distribution of flat-topped light beams passing through a paraxial ABCD optical system has been derived. The lens system is taken as an example,the analytical expression of the focusing field distribution of flat-topped light beams is given. The focusing properties of flat-topped light beams have been analyzed in detail.
A fixed output power laser supply with improved power factor
NIU Zeng-qiang, PENG Wen-da, NIU Han-ben
2004, 28(2): 147-149,169.
Abstract:
The design principle and circuit structure about the laser power supply with fixed output power and improved power factor is presented in this paper.The output power of this laser power supply cannot be changed as the line voltage is shifted.So this laser power supply may make the output laser energy less in stable.Moreover,the laser power supply with improved power factor might effectively restrain the harmonic noise and reduce the input ampere-capacity of power equipment and so on.
Study on the theoretical thickness of the free limiting layer and experiments in laser shock processing
HUA Yin-qun, CHEN Rui-fang, YANG Ji-chang, ZHANG Yong-kang, WEI Yi
2004, 28(2): 150-152.
Abstract:
This paper studies on the thickness of the free limiting layer in the laser shock processing(LSP).The optimum thickness of the free limiting layer was obtained, after the relations are researched among the shocking pressure by the coating vaporization and explosion and the adherent force between the workpiece and the free limiting layer and the behaviors of the free limiting layer.Namely, not only the optimal effect of the LSP is obtained,but also the objective to clean the free limiting layer only once safely and effectually can be realised,which is proved by the experiment.
Photo wave propagation in one dimension random photonic crystal
FANG Yun-tuan, SHEN Ting-gen, LIN Guo-hua
2004, 28(2): 153-155.
Abstract:
Photo wave propagation in one dimension random photonic crystal is studied with eigen matrix method. Compared with periodical structure,the band gap fades away and the transmitting rate is relate to the random degree,frequency and number of medium layers.
Modulation instability in decreasing dispersion fiber with different profiles
REN Zhi-jun, WANG Jing, YANG Ai-ling, WANG Zhen-li
2004, 28(2): 156-159.
Abstract:
The gain spectrum of modulation instability is studied in the condition of decreasing dispersion fiber with different group dispersion profiles.The gain spectral width is found to vary as the type of the group dispersion profile changes.The spectral width is discovered simply relevant to transmitted distance for the type of exponential,and the curve of spectral width versus transmitted distance has a vale for the type of linear,Guassian and logarithm,but a firstly broadening and then a gradual decrease is gotten for the type of hyperbolic.Besides the mechanism of pulse compression is interpreted by means of modulation instability.
A narrow linewidth external-cavity semiconductor laser
JIANG Peng-fei, ZHAO Wei-rui, ZHANG Jing-juan, XIE Fu-zeng
2004, 28(2): 160-161.
Abstract:
We introduce the external-cavity semiconductor laser with feedback of Littrow configuration. The spectral line width is narrowed to be less than 1.2MHz and the output stability is remarkably enhanced. We also propose a new complex-cavity method which can greatly narrow the line width of a semiconductor laser.
Simulation and verification of the temperature field in laser hardening
WANG Xiu-feng, LÜ Xiao-dong, CHEN Guang-nan, HU Shi-guang
2004, 28(2): 162-165.
Abstract:
We introduce the external-cavity semiconductor laser with feedback of Littrow configuration. The spectral line width is narrowed to be less than 1.2MHz and the output stability is remarkably enhanced. We also propose a new complex-cavity method which can greatly narrow the line width of a semiconductor laser.
A coaxial measuring system for a hole using non-diffracting beam
ZHANG Xin-bao, LI Zhu
2004, 28(2): 166-169.
Abstract:
Using the non-diffracting beam along the axes z,a spatial straight line can be reasonably obtained.Furthermore,the non-diffracting beam has better tolerance properties to the drift of laser beam than that of the common collimated laser beam and its optic axes is more stable than the enlarged laser beam.So it is more suitable to be used as the spatial datum-line for straightness error or coaxiality error measurement.Based on the non-diffracting beam datum-line and combining roundness measuring technology with its amending technology,a high precision coaxial measurement method for a hole has been proposed in this paper.The principle of the measuring system is introduced and theoretical error analysis and test are made to verify it.
Study of Stokes generation in Nd:YAG fourth harmonic(266nm) pumped H2
ZHU Xiao-zheng, LOU Qi-hong, YE Zhen-huan, DONG Jing-xing, WEI Yun-rong
2004, 28(2): 170-172,176.
Abstract:
The stimulated Raman scattering (SRS) in H2 pumped by the fourth harmonic of Nd:YAG laser (266nm) is investigated.The wavelength of the pump laser has been shifted into 200nm~595nm wavelength region.When the pump laser is operated at laser energy of 22mJ,five orders of Stokes and three orders of anti-Stokes have been observed.The corresponding output energy of the first order Stokes (299nm),the second order Stokes (341nm) and the first order anti-Stokes (239nm) was 3mJ,6.1mJ and 0.8mJ respectively.The relationships between the pressure of H2 and energy of each Stokes were investigated.Moreover,the circle beam spots have been observed.
Output characteristics of Yb3+ doped double-clad fiber grating laser
ZHANG Jun, PAN Yu-zhai, HU Gui-jun, ZHANG Liang, LI Shou-chun, WANG Li-jun
2004, 28(2): 173-176.
Abstract:
In the experiment,we adjust LD's wavelength by control of temperature and analyze the characteristics of fiber laser. The fiber laser in this experiment is composed of a high-power LD pumped with output wavelength of 970nm and a double-clad fiber spliced fiber Bragg gratings (FBGs) at both ends. Experimentally through a taper fiber,we have realized 5.1W of output power at 1100nm,with the highest conversion efficiency of 63%.
Thermal effect research of Nd3+ doped laser crystals in end-pumped all-solid-state lasers
SHI Peng, LI Long, GAN An-sheng, LI Dong-liang, BAI Jin-tao
2004, 28(2): 177-180.
Abstract:
In diode pumped all-solid-state laser system laser crystal absorbing diode pumped energy will generate laser oscillation,simultaneously quite a part of pump energy will be translated into heat which is dissipated inside crystal.The thermal phenomena induced thermal effects seriously influence laser's performance and quality.According to laser crystal end-pumping mode analysis,laser crystal's interior temperature field and thermal distortion field calculation means are obtained by semi-analytical thermal analysis method.Under the same working conditions several typical Nd-ion doped laser crystal's temperature field and end face thermal distortion field as well as reasons of discrepancy are quantitatively analyzed.The analysis method and research results can also be applied to analyze temperature field and thermal distortion field of inner thermal source with axis-symmetrical profile models.The work will supply theory groundwork for design of diode pumped all-solid-state lasers.
The coupling of Gaussian beam between fibers
WU Jun-fang, WANG Ying, ZHANG Ling
2004, 28(2): 181-183.
Abstract:
There are several means for Gaussian beam to couple between optical fibers.One of these is collimating-focusing system using lenses.To decide the parameters of the coupling system, the Gaussian beam's change through a single lens is studied.It indicates that the waist width passing through the lens is decided by several variables,which is illustrated.By analyzing the illustration, the general principle to select the parameters is found.At last, the conclusion is used to resolve an instance.
Achromatic analysis of the two-in-one composite 1/4 wave-plate
XUE Dong, LI Guo-hua, HAO Dian-zhong, WANG Wei
2004, 28(2): 184-185,192.
Abstract:
Through the Jones vector variation of incident light and emergent light,a achromatic theoretical formula for composite wave-plate is deduced.The feasibility of the method and the direction for use are discussed.
Optical design and experiment of microlens array for CCD image sensors
KE Cai-jun, YI Xin-jian, LAI Jian-jun
2004, 28(2): 186-189.
Abstract:
To increase the fill factor of CCD image sensor greatly,the structure of microlens array matched with the CCD is designed and compared with the experimental results.The results show that the microlens integrated with CCD can improve the fill factor of visible CCD by a factor of 2.9 and the relative spectrum response has an increase of 0.2.The design indicates that the microlens array can optimize the intensity contribution and improve the fill factor and the photoelectricity performances of CCD sensors remarkably.
Study on demodulation system of laser Doppler
HE Shun-zhong, YAO Xin, JIANG Cheng-zhi, DU Zhen-hui, LIU Jin-feng
2004, 28(2): 190-192.
Abstract:
To improve the specifications of seismometers,laser Doppler measurement technique and weak signal detect technology and etc are studied,and a differential Doppler demodulation system with a LD is designed.In this system,more Doppler signals are received and more space resolving power are achieved because of adopting Gaussian beams focus and lens with large diameter as well as acoustooptic modulation technology and lock-in amplifier used to improve SNR.It has characteristics of simple structure,fixing and adjusting convenience,high use-ratio of light power and space resolution.The measurable ranges of frequency and amplitude are 0.5Hz~1000Hz, 2μm~5mm respectively,and the corresponding measurement precisions are 0.6%,1% respectively.
The study of constant temperature and current control system for SLED
SONG Shi-de, YU Qing-xu
2004, 28(2): 193-195.
Abstract:
The stability of optical sources is required in many fiber optic sensor systems.This paper describes a high precision constant temperature and constant current control system for SLED, which is based on a singlechip computer.The system is able to control the temperature variation within ±0.01℃ and current drift under ±0.02mA by utilizing PID control algorithm, which meets the demands of the reliability and stability of the optical sources for sensor systems.
Methods of improving the depth resolution in optical 3-D profilometry with laser sheet
ZOU Xiao-ping, SU Xian-yu, ZHANG Qi-can
2004, 28(2): 196-198,224.
Abstract:
Methods of reducing the speckle noise and improving the depth resolution in optical 3-D profilometry with laser sheet are proposed in the paper.Speckle is caused by object's micro-structure,with more less-correlated random structure co-interference in the imaging field,the speckle can be depressed greatly.As proved by experiments,combined the method of appreciably sacrificing the lateral resolution and dynamic image capture,the depth resolution can be effectively improved.
MG2 factor of truncated Laguerre-Gaussian beams
LUO Shi-rong, LÜ Bai-da
2004, 28(2): 199-201.
Abstract:
The generalized beam propagation factor(MG2 factor) of circularly symmetric truncated Laguerre-Gaussian beams is studied using the generalized truncated second-order moments method. A closed-form expression for the MG2 factor is derived and illustrated with numerical example. It is found that the MG2 factor of circularly symmetric truncated Laguerre-Gaussian beams depends on the truncation parameter and beam order,and asymptotically approaches the value of circularly symmetric untruncated Laguerre-Gaissain beams as the truncated parameter increases.
Measurement of linear thermal expansion coefficient of low expansion materials using interferometery
YAN Qin, LI Dong-feng
2004, 28(2): 202-204.
Abstract:
The linear thermal expansion coefficient of materials is very important in the fields of precision instruments and high precision experiments.To measure the linear thermal expansion coefficient of some ultra low expansion(ULE)materials,the laser interferometer is usually used.In our experiments,the two interferential arms of the laser interferometer are fixed on one bracket,whose the purpose is to compensate the optical path changes caused by other effect except the elongation of the materials.Using this interferometer,not only the linear thermal expansion of the bracket can be counteracted,but also the ground vibration can be counteracted effectively.We measure the linear thermal expansion coefficient of the materials at the level of 10-6/℃ by this laser interferometer.If the technique of the experiment is improved on and interferential stripes are stabilized,this kind of interferometer can used to measure the linear thermal expansion coefficient at higher level.
Optical disk array system with parallel multi-controllers
MENG Yu, WANG Tao, HUANG Lei, GONG Ma-li
2004, 28(2): 205-207.
Abstract:
This paper presents a novel optical disk array with parallel multi-controllers.There is always only one controller to master all the disks in the traditional optical disk array system,thus the disk number is limited,so is the overall performance.In this paper,we propose a new system using parallel multi-disk controller to compose an optical disk array.The overall system complexity could be deduced drastically.The final experiment demonstrates that this novel system can get a much better performance than the traditional one.
Finite element analysis of laser medium’s thermal-lens
ZHU Guang-zhi, CHEN Pei-feng, ZOU Xue-fen, ZHU Chang-hong
2004, 28(2): 208-210,217.
Abstract:
The thermal-lens effects of side-pumped solid-state lasers are studied and heat exchange equation is established.The temperature and thermal stress of laser medium in different pumping condition are analyzed by finite element method.Some compensation on thermal-lens effects is discussed.Thermal focal distance in different compensation condition is compared through experiment.
Model of effective refractive indices of nanoporous polymer films
LIU Yong-jun, ZHU Da-qing, YANG Zhen-yu, LU Dong-sheng
2004, 28(2): 211-213.
Abstract:
In this paper, the methods for effective refractive indices of multi-phase medium are applied to study the relationship between the effective refractive indices and pore-ratio of nanoporous polymer films made of PS,PMMA and nanopores. And the formula for the relationship between the effective refractive indices and pore-ratio of nanoporous polymer films has been obtained. What's more, the results of the formula are in coincidence with the experimental results.
Selecting aspects of buffer gas in optically pumped far-infrared laser
ZHANG Xun, ZHANG Ping, XIAO Dong-mei, CHEN Wei-bin, LUO Xi-zhang
2004, 28(2): 214-217.
Abstract:
Based on semi-classical density matrix theory and SSH method, buffer gas effect of optically pumped far-infrared laser was theoretically studied and the effect of depth of potential well and radius of collision on buffer gas was analyzed.The result would do favor to find high-efficient buffer gas of optically pumped far-infrared laser and also had some instruction to its application.
Target detection algorithm of laser echo
PING Qing-wei, HE Pei-kun, ZHAO Bao-jun
2004, 28(2): 218-220.
Abstract:
The threshold algorithm of the target detection is often used to detect target echo signals.Its performance is based on signals-noise ratio.When signals-noise ratio is great than 6.7,the target can be detected.In order to increase the signals-noise ratio,matching filter is often used.If the system is narrow band system,the noise is color noise and matching filter cannot be used.Therefore,the signals-noise ratio cannot be increased.However,the geometrical characteristic of the laser echo signal is different with the noise.This paper advises the algorithm that detects the target by the geometrical characteristic.When signals-noise ratio is great than 2,this algorithm can detect target.This algorithm has been used in practice.
Analysis of erbium-doped superfluorescent fiber source in double-pass backward configuration
XING Li-feng, XIAO Rui, FENG Ying
2004, 28(2): 221-224.
Abstract:
Erbium-doped superfluorescent fiber sources(SFS) in double-pass backward(DPB) configuration are characterized in output power,spectrum linewidth and mean wavelength through theoretical simulation.The results indicate that DPB SFSs mean wavelength can be adjusted insenstitive to pump power by properly adjusting the erbium-doped fiber(EDF) length,SFS with double-pass backward configuration made by us is also reported.