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RSS2006 Vol. 30, No. 4
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2006, 30(4): 337-339,343.
[Abstract]
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Abstract:
In order to investigate the possibility of a lateral shear interferometer,which is based on a birefringence crystal shear generator,to be applied to on-machine surface measurement,optical models of the interferometer for light propagation and surface measurement are derived.Its anti-vibration characteristics are analyzed,and a vibration table to simulate different vibration conditions is set up,on which many experiments for surface measurement under different vibration conditions are conducted.The analysis and experimental testing verify the advanced anti-vibration characteristics of the interferometer for on-machine surface measurement.
In order to investigate the possibility of a lateral shear interferometer,which is based on a birefringence crystal shear generator,to be applied to on-machine surface measurement,optical models of the interferometer for light propagation and surface measurement are derived.Its anti-vibration characteristics are analyzed,and a vibration table to simulate different vibration conditions is set up,on which many experiments for surface measurement under different vibration conditions are conducted.The analysis and experimental testing verify the advanced anti-vibration characteristics of the interferometer for on-machine surface measurement.
2006, 30(4): 340-343.
Abstract:
A 3-D shape measurement method using max-difference color-coding structured light is suggested to avoid complicated phase-recover process in three-dimension sensing.A pattern of exclusive color sequence is obtained and a relationship between spatial location and color is established.The difference of neighboring colors is maximized so that they can be distinguished easily.Projecting the color-combination fringe to the object and reference plane respectively,two images are taken.The height of the object can be recovered by edge detection and triangulation.This method has been implemented and proved to be fast,precise and noise-immune.
A 3-D shape measurement method using max-difference color-coding structured light is suggested to avoid complicated phase-recover process in three-dimension sensing.A pattern of exclusive color sequence is obtained and a relationship between spatial location and color is established.The difference of neighboring colors is maximized so that they can be distinguished easily.Projecting the color-combination fringe to the object and reference plane respectively,two images are taken.The height of the object can be recovered by edge detection and triangulation.This method has been implemented and proved to be fast,precise and noise-immune.
2006, 30(4): 344-346,359.
Abstract:
In order to investigate the weldability of a new ultra-low carbon bainitic(NULCB) steel,the steel is welded with a 3kW CO2 laser and the microstructure and mechanical properties of the weld joint are investigated.The experimental results indicate that the hardness of welded joint is higher than that of the base metal while the laser heat input is between 120J/mm and 600J/mm,and no obvious zone is softened after laser welding.The microstructure of the weld metal and the coarse-grained heat-affected zone are both granular bainite that consists of the bainite lath and the M-A constituent.When the heat input increases from 120J/mm to 600J/mm,the average width,gross and shape parameter of M-A increases,but the line density decreases.As the heat input of laser welding increases,the impact energy of the weld metal increases at first and then decreases,and it is higher than that of the base metal under appropriate laser welding conditions.
In order to investigate the weldability of a new ultra-low carbon bainitic(NULCB) steel,the steel is welded with a 3kW CO2 laser and the microstructure and mechanical properties of the weld joint are investigated.The experimental results indicate that the hardness of welded joint is higher than that of the base metal while the laser heat input is between 120J/mm and 600J/mm,and no obvious zone is softened after laser welding.The microstructure of the weld metal and the coarse-grained heat-affected zone are both granular bainite that consists of the bainite lath and the M-A constituent.When the heat input increases from 120J/mm to 600J/mm,the average width,gross and shape parameter of M-A increases,but the line density decreases.As the heat input of laser welding increases,the impact energy of the weld metal increases at first and then decreases,and it is higher than that of the base metal under appropriate laser welding conditions.
2006, 30(4): 347-350.
Abstract:
In order to study influence of experimental parameters on photo-thermal interferometric detection,according to interference principle of equal thickness,a theory model is set up by means of Seidel aberration of tilt.After various probe beams are investigated,a universal light model is proposed by means of random function,and uniformity of the light source is defined.Based on this model,it is simulated that interferometric experimental phenomena change with various probe beam,and the influence of probe's uniformity is analyzed on interferometric measurement,which show there are no difference among various probe beam.On the other hand,the influence of detector's aperture on interferometric measurement is analyzed.Results show it is the best when radius of detector's aperture is 0.315cm.Under this condition,photo-thermal signal descends monotonously during fine scale photo-thermal displacement of 0~0.6λ,and the contrast of interferometric stripe is better.Under weak absorption,a simple experiential equation between photo-thermal signal and photo-thermal displacement can be concluded by curve fitting.
In order to study influence of experimental parameters on photo-thermal interferometric detection,according to interference principle of equal thickness,a theory model is set up by means of Seidel aberration of tilt.After various probe beams are investigated,a universal light model is proposed by means of random function,and uniformity of the light source is defined.Based on this model,it is simulated that interferometric experimental phenomena change with various probe beam,and the influence of probe's uniformity is analyzed on interferometric measurement,which show there are no difference among various probe beam.On the other hand,the influence of detector's aperture on interferometric measurement is analyzed.Results show it is the best when radius of detector's aperture is 0.315cm.Under this condition,photo-thermal signal descends monotonously during fine scale photo-thermal displacement of 0~0.6λ,and the contrast of interferometric stripe is better.Under weak absorption,a simple experiential equation between photo-thermal signal and photo-thermal displacement can be concluded by curve fitting.
2006, 30(4): 351-354.
Abstract:
The properties and advantages of optical pumping semiconductor vertical-external-cavity surface-emitting laser(VECSEL) are introduced and the latest device development is demonstrated.On the basis of these analyses,the application potential and technology direction in the areas are pointed out.
The properties and advantages of optical pumping semiconductor vertical-external-cavity surface-emitting laser(VECSEL) are introduced and the latest device development is demonstrated.On the basis of these analyses,the application potential and technology direction in the areas are pointed out.
2006, 30(4): 355-359.
Abstract:
In order to explore process of laser bending steel tubes the temperature field and stress strain field are analysed with method of numerical simulation.Dynamic process of laser bending the steel tube is researched.The rule of elastic and plastic distortion at top,middle and bottom in tube thickness direction is analyzed.The results show that the compress plastic distortion is produced along tube thickness direction at section of laser scanning and compress plastic distortion of the bottom is greater than that of the top under giving technical parameter.The!effect of the laser parameter on the bending angle is researched.The bending angle can be increased along with increasing the laser power or scanning angle.
In order to explore process of laser bending steel tubes the temperature field and stress strain field are analysed with method of numerical simulation.Dynamic process of laser bending the steel tube is researched.The rule of elastic and plastic distortion at top,middle and bottom in tube thickness direction is analyzed.The results show that the compress plastic distortion is produced along tube thickness direction at section of laser scanning and compress plastic distortion of the bottom is greater than that of the top under giving technical parameter.The!effect of the laser parameter on the bending angle is researched.The bending angle can be increased along with increasing the laser power or scanning angle.
2006, 30(4): 360-362,365.
Abstract:
In order to get the information of index of refraction,we measure the properties of birefringence of LiNbO3and LiNbO3 waveguide,using UT300-FPD ellipsometry.Firstly,we made model of LiNbO3 and fit the results,so we have the index of refraction from 190nm~1700nm.Secondly,based on the model of the first step,we readily obtain the model of LiNbO3 waveguide and the distribution of the index of refraction.The work we have done provide useful information for the development of LiNbO3 waveguide as photon devices.
In order to get the information of index of refraction,we measure the properties of birefringence of LiNbO3and LiNbO3 waveguide,using UT300-FPD ellipsometry.Firstly,we made model of LiNbO3 and fit the results,so we have the index of refraction from 190nm~1700nm.Secondly,based on the model of the first step,we readily obtain the model of LiNbO3 waveguide and the distribution of the index of refraction.The work we have done provide useful information for the development of LiNbO3 waveguide as photon devices.
2006, 30(4): 363-365.
Abstract:
Bragg solitons are formed by the balance between the nonlinear effect and dispersion in the fiber Bragg grating,which reveals some important physical phenomena and offers its application in the optical buffer.Based on the nonlinear coupled-mode equations,the analytical solution of Bragg solitons is given.With the analytical solution as an initial condition,the stability of Bragg solitons in the fiber Bragg grating is numerically investigated.There are three transmission modes of Bragg solitons,such as stable mode,multiple vibrating mode and scattering mode.The evolutions of Bragg solitons in the multiple vibrating mode and scattering mode are analyzed.This research gives some valuable results for novel device design and related experiments.
Bragg solitons are formed by the balance between the nonlinear effect and dispersion in the fiber Bragg grating,which reveals some important physical phenomena and offers its application in the optical buffer.Based on the nonlinear coupled-mode equations,the analytical solution of Bragg solitons is given.With the analytical solution as an initial condition,the stability of Bragg solitons in the fiber Bragg grating is numerically investigated.There are three transmission modes of Bragg solitons,such as stable mode,multiple vibrating mode and scattering mode.The evolutions of Bragg solitons in the multiple vibrating mode and scattering mode are analyzed.This research gives some valuable results for novel device design and related experiments.
2006, 30(4): 366-369.
Abstract:
In order to achieve much higher output power to satisfy the application requirements,the performances of erbium/ytterbium co-doped double-cladding fiber lasers(EY-DCFLs) are studied experimentally and theoretically.By using the EY805 model erbium/ytterbium co-doped multi-mode double-cladding fiber manufactured by INO,Canada as the gain medium,it is described that the output power is a function of the input pump power and fiber length.The maximum output power is about 3.5W by using a 1.8m fiber,with an optical to optical conversion efficiency of 31.8%.Numerical analysis of this EY-DCFL is also performed based on the rate and propagation equations.The calculated output powers of about 4.4W and conversion efficiency of 40% for the same fiber are a little larger than the experimental results.Then further optimization measures of the EY-DCFL are discussed,such as preparing of the fiber-end well,adding dichroic mirror at the output end and making fiber Bragg gratings directly in the fiber core.The above results are very important for the utilization and performance improvement of EY-DCFL.
In order to achieve much higher output power to satisfy the application requirements,the performances of erbium/ytterbium co-doped double-cladding fiber lasers(EY-DCFLs) are studied experimentally and theoretically.By using the EY805 model erbium/ytterbium co-doped multi-mode double-cladding fiber manufactured by INO,Canada as the gain medium,it is described that the output power is a function of the input pump power and fiber length.The maximum output power is about 3.5W by using a 1.8m fiber,with an optical to optical conversion efficiency of 31.8%.Numerical analysis of this EY-DCFL is also performed based on the rate and propagation equations.The calculated output powers of about 4.4W and conversion efficiency of 40% for the same fiber are a little larger than the experimental results.Then further optimization measures of the EY-DCFL are discussed,such as preparing of the fiber-end well,adding dichroic mirror at the output end and making fiber Bragg gratings directly in the fiber core.The above results are very important for the utilization and performance improvement of EY-DCFL.
2006, 30(4): 370-372,376.
Abstract:
With the ever-increasing needs of high power diode laser source,it is important to obtain symmetric diode laser beam with high power so that a kind of beam-shaping technique with isosceles right-angled prism group has been used to achieve this aim.The experiment presents that the beam-quality is nearly equal for both the fast and slow axes,and the reshaping efficiency is up to 90%.Diode lasers with improved beam-quality can be applied as the pumping source in many high-power solid lasers and fiber lasers.
With the ever-increasing needs of high power diode laser source,it is important to obtain symmetric diode laser beam with high power so that a kind of beam-shaping technique with isosceles right-angled prism group has been used to achieve this aim.The experiment presents that the beam-quality is nearly equal for both the fast and slow axes,and the reshaping efficiency is up to 90%.Diode lasers with improved beam-quality can be applied as the pumping source in many high-power solid lasers and fiber lasers.
2006, 30(4): 373-376.
Abstract:
The major concern during laser irradiation of teeth is the high potential of tissue overheating resulting high temperatures that can spread in toward the dentin,causing irreversible damage to cells presented in the pulp chamber and leading to cell death,so the related laser irradiation parameters should be controlled strictly.The thermal diffusion model in dentin is built and the distribution of temperature field at the surface and subsurface region of dentin irradiated by Nd:YAG laser with different parameters is simulated numerically using Crank-Nicolson finite differential method.Calculation results show that the final temperature at the surface of dentin and at the pulp chamber wall depends on the pulse duration,interval and numbers.Laser irradiation by dividing total energy into several laser pulses leads to lower temperature at the dentin surface,while the reverse situation occurs at pulp region,the higher temperature is achieved with increasing pulse numbers.The related opto-thermal mechanism is discussed and it is put forward that controlling the energy of the single laser pulse is the optimum measure for opto-thermal ablation of dentin.
The major concern during laser irradiation of teeth is the high potential of tissue overheating resulting high temperatures that can spread in toward the dentin,causing irreversible damage to cells presented in the pulp chamber and leading to cell death,so the related laser irradiation parameters should be controlled strictly.The thermal diffusion model in dentin is built and the distribution of temperature field at the surface and subsurface region of dentin irradiated by Nd:YAG laser with different parameters is simulated numerically using Crank-Nicolson finite differential method.Calculation results show that the final temperature at the surface of dentin and at the pulp chamber wall depends on the pulse duration,interval and numbers.Laser irradiation by dividing total energy into several laser pulses leads to lower temperature at the dentin surface,while the reverse situation occurs at pulp region,the higher temperature is achieved with increasing pulse numbers.The related opto-thermal mechanism is discussed and it is put forward that controlling the energy of the single laser pulse is the optimum measure for opto-thermal ablation of dentin.
2006, 30(4): 377-380.
Abstract:
The key technology to make a micro polarized beam splitter(PBS)used as optical switcher and polarization-free isolator in the DWDM system is discussed.The optical film is designed with optimum method.The tolerance of the layer is modeled through Monte Carlo method in order to obtain simple manufacture process.The film thickness error of the each layer is obtained by calculating the Macleod maximum sensitivity.The film thickness is controlled by modeling the optical monitoring processes.A practical cemented prism is designed,and a PBS prism with advanced technique parameters is obtained.The results show that the optical cold machining for the prism is the base to make the PBS,the key issue and difficulty are optical film design and coating,and it is also important to cement the prism.
The key technology to make a micro polarized beam splitter(PBS)used as optical switcher and polarization-free isolator in the DWDM system is discussed.The optical film is designed with optimum method.The tolerance of the layer is modeled through Monte Carlo method in order to obtain simple manufacture process.The film thickness error of the each layer is obtained by calculating the Macleod maximum sensitivity.The film thickness is controlled by modeling the optical monitoring processes.A practical cemented prism is designed,and a PBS prism with advanced technique parameters is obtained.The results show that the optical cold machining for the prism is the base to make the PBS,the key issue and difficulty are optical film design and coating,and it is also important to cement the prism.
2006, 30(4): 381-384,389.
Abstract:
From the point of view of Fourier optics,laser beam coherent combination by binary phase grating is discussed and the design method of phase grating is studied.Using the genetic-simulated annealing algorithm,the optimum parameters of grating are obtained.Then,the simulation results of diffraction and combination are presented.The error analysis shows that it will influences the diffraction efficiency.For laser beam combination,binary phase grating is simple,flexible and can greatly improve the laser beam's power density and the system integration.
From the point of view of Fourier optics,laser beam coherent combination by binary phase grating is discussed and the design method of phase grating is studied.Using the genetic-simulated annealing algorithm,the optimum parameters of grating are obtained.Then,the simulation results of diffraction and combination are presented.The error analysis shows that it will influences the diffraction efficiency.For laser beam combination,binary phase grating is simple,flexible and can greatly improve the laser beam's power density and the system integration.
2006, 30(4): 385-389.
Abstract:
In order to investigate the generation mechanism of the cracks on the surface of proton-exchanged(PE) wave-guides on the x-cut lithium niobate substrate and the influence on the characteristics of wave-guide.The crystal microstructure,the intensity of the cracks on the surface,the existing manner of hydrogen ion and the variation of density of the annealing proton-exchanged(APE) wave-guide are studied by means of contrast experiments,observation on the surface of wave-guide,XRD(X-ray diffraction) analysis of the crystal phase in the wave-guide,infrared absorption spectra analysis of wave-guide,and so on.The results show that the cracks are made by the stress parallel with the principal cleavage plane of lithium niobate,which have four characteristics:made in the PE process,parallel with each others,deteriorated in proportion to the time of PE process and being ameliorated somewhat in the annealing process.It is also shown that the cracks are the macroscopical representation of the stress and that the annealing process could influence the existing manner of hydrogen ion and its density variation,alter the crystal phases and the stress in the wave-guide,and improve the performance of the wave-guide.It is concluded that multiple-phase coexistence and the difference of the crystal lattice coefficient resulted in the stress and then lead to the crackand that the smallest distortion in crystal lattice,the lowest stress and the α phase wave-guide may have the lowest possibility to bring out crack,and can improve the performance of the wave-guide.
In order to investigate the generation mechanism of the cracks on the surface of proton-exchanged(PE) wave-guides on the x-cut lithium niobate substrate and the influence on the characteristics of wave-guide.The crystal microstructure,the intensity of the cracks on the surface,the existing manner of hydrogen ion and the variation of density of the annealing proton-exchanged(APE) wave-guide are studied by means of contrast experiments,observation on the surface of wave-guide,XRD(X-ray diffraction) analysis of the crystal phase in the wave-guide,infrared absorption spectra analysis of wave-guide,and so on.The results show that the cracks are made by the stress parallel with the principal cleavage plane of lithium niobate,which have four characteristics:made in the PE process,parallel with each others,deteriorated in proportion to the time of PE process and being ameliorated somewhat in the annealing process.It is also shown that the cracks are the macroscopical representation of the stress and that the annealing process could influence the existing manner of hydrogen ion and its density variation,alter the crystal phases and the stress in the wave-guide,and improve the performance of the wave-guide.It is concluded that multiple-phase coexistence and the difference of the crystal lattice coefficient resulted in the stress and then lead to the crackand that the smallest distortion in crystal lattice,the lowest stress and the α phase wave-guide may have the lowest possibility to bring out crack,and can improve the performance of the wave-guide.
2006, 30(4): 390-391,401.
Abstract:
In order to simulate the diffraction field of apertured beam more precisely,the higher-order field can simulate the diffraction field of apertured beam by an appropriate increase of the expansion order M as the propagation distance z decreases.For different values of the propagation distance z,the expansion order M can be chosen according to the inequality proposed.Taking the super-Gaussian beam as an example,numerical calculation is performed to illustrate the application of the theoretical formulations.The results obtained in this paper are useful for studying the propagation of optical beam diffracted by an aperture.
In order to simulate the diffraction field of apertured beam more precisely,the higher-order field can simulate the diffraction field of apertured beam by an appropriate increase of the expansion order M as the propagation distance z decreases.For different values of the propagation distance z,the expansion order M can be chosen according to the inequality proposed.Taking the super-Gaussian beam as an example,numerical calculation is performed to illustrate the application of the theoretical formulations.The results obtained in this paper are useful for studying the propagation of optical beam diffracted by an aperture.
2006, 30(4): 392-394.
Abstract:
Broad bandwidth source(BBS) is usually used to watch and control the fabrication of fiber gratings.A home-made Yb3+-doped double-cladding fiber superfluorescent broad bandwidth source is reported.The BBS,with bandwidth of about 75nm at the maximum output power,is pumped by a 971nm laser diode.The BBS outputs high power with a flat superfluorescent spectrum in the range of 10nm near the central wavelength of 1085nm.Then the BBS is used to watch and control the fabrication of single-mode and multi-mode fiber Bragg gratings and the results are satisfied.
Broad bandwidth source(BBS) is usually used to watch and control the fabrication of fiber gratings.A home-made Yb3+-doped double-cladding fiber superfluorescent broad bandwidth source is reported.The BBS,with bandwidth of about 75nm at the maximum output power,is pumped by a 971nm laser diode.The BBS outputs high power with a flat superfluorescent spectrum in the range of 10nm near the central wavelength of 1085nm.Then the BBS is used to watch and control the fabrication of single-mode and multi-mode fiber Bragg gratings and the results are satisfied.
2006, 30(4): 395-397.
Abstract:
To study the effect of He-Ne laser radiation on differential thermal analysis(DTA) thermal parameters of folium isatidis exposed to ultraviolet B(UV-B) radiation,and further discuss the mechanism of laser biology,isatis indigotica seedlings exposed to UV-B radiation are treated with He-Ne laser.The experiments are divided into four groups,i.e.,comparison group,laser-treated group,UV-B treated group and UV-B and laser hybrid treated group.All DTA curves of the four groups represent one endothermic peak and two exothermic peaks and DTA parameters are different significantly among four treatments.The sequence of the total enthalpy value of the four treatments from the large to the small is laser-treated group,UV-B and laser hybrid treated group,comparison group,UV-B treated group,which shows that laser plays repair role on the seedlings lesion by UV-B damage.
To study the effect of He-Ne laser radiation on differential thermal analysis(DTA) thermal parameters of folium isatidis exposed to ultraviolet B(UV-B) radiation,and further discuss the mechanism of laser biology,isatis indigotica seedlings exposed to UV-B radiation are treated with He-Ne laser.The experiments are divided into four groups,i.e.,comparison group,laser-treated group,UV-B treated group and UV-B and laser hybrid treated group.All DTA curves of the four groups represent one endothermic peak and two exothermic peaks and DTA parameters are different significantly among four treatments.The sequence of the total enthalpy value of the four treatments from the large to the small is laser-treated group,UV-B and laser hybrid treated group,comparison group,UV-B treated group,which shows that laser plays repair role on the seedlings lesion by UV-B damage.
2006, 30(4): 398-401.
Abstract:
A novel type of 16-channel,100GHz spaced dense wavelength division demultiplexer,composed of 100GHz optical interleaver and 200GHz dielectric filters is presented,which can easily meet the demand that the amount of demultiplexed wavelengths gets larger and the spacing of them gets narrower.An optical interleaver is used to enlarge the spacing of demultiplexed channels,and several 200GHz dielectric filters are cascaded on the output of interleaver to separate the different wavelengths.The experimental results show that this device has excellent performances and suits the upgrade of dense wavelength division multiplex(DWDM) systems.
A novel type of 16-channel,100GHz spaced dense wavelength division demultiplexer,composed of 100GHz optical interleaver and 200GHz dielectric filters is presented,which can easily meet the demand that the amount of demultiplexed wavelengths gets larger and the spacing of them gets narrower.An optical interleaver is used to enlarge the spacing of demultiplexed channels,and several 200GHz dielectric filters are cascaded on the output of interleaver to separate the different wavelengths.The experimental results show that this device has excellent performances and suits the upgrade of dense wavelength division multiplex(DWDM) systems.
2006, 30(4): 402-405.
Abstract:
Fabrication of nano-SiC bulk material by selective laser sintering technology with nano-SiC powder is achieved.The microstructure of laser-sintering nano-SiC ceramic coating is examined by means of X-ray diffraction analyses,scanning electron microscopy.At the same time,the laser sintering procedure of nano-SiC powder and effect of technique parameters are investigated.The results show that the nano-SiC powder materials can be sintered to bulk material with the proper process parameters,the crystal size of the production is almost kept the same as that of nano-SiC powder,but some power is decomposed to nano-structural silicon and nano-structural carbon.
Fabrication of nano-SiC bulk material by selective laser sintering technology with nano-SiC powder is achieved.The microstructure of laser-sintering nano-SiC ceramic coating is examined by means of X-ray diffraction analyses,scanning electron microscopy.At the same time,the laser sintering procedure of nano-SiC powder and effect of technique parameters are investigated.The results show that the nano-SiC powder materials can be sintered to bulk material with the proper process parameters,the crystal size of the production is almost kept the same as that of nano-SiC powder,but some power is decomposed to nano-structural silicon and nano-structural carbon.
2006, 30(4): 406-408.
Abstract:
For laser cutting thin quartz glass plates precisely,its principle is discussed,how to choose laser cutting equipment is introduced according to the quartz glass' optical transmissivity,i.e.,the laser's wave length should be in 5μm～20μm for laser cutting application.The specimen laser cutting experiments show that it is feasible to cut thin quartz glass plates pricisely with laser cutting technique with accuracy of better than 20μm and central symmetry of less than 3μm.The experimental results and choosing method are helpful for precision quartz laser cutting application and development of laser cutting equipment.
For laser cutting thin quartz glass plates precisely,its principle is discussed,how to choose laser cutting equipment is introduced according to the quartz glass' optical transmissivity,i.e.,the laser's wave length should be in 5μm～20μm for laser cutting application.The specimen laser cutting experiments show that it is feasible to cut thin quartz glass plates pricisely with laser cutting technique with accuracy of better than 20μm and central symmetry of less than 3μm.The experimental results and choosing method are helpful for precision quartz laser cutting application and development of laser cutting equipment.
2006, 30(4): 409-411.
Abstract:
For the purpose of simplifying the cavity structure,enhancing the stability especially on the hot stability,enlarging the basic mode volume,improving the beam quality of the high power lasers,a right angle cone mirror laser cavity with a right-angle-cone mirror as the totally reflecting mirror and a parallel flat partially reflecting mirror as the output mirror is introduced.The results of the experiments show that when the misalignment angle of the cone mirror turns to 37.2′,the decrease of the single-pulse output energy of the plane-cone folded cavity laser is less than 5% and the near-field beam patterns have little change;the analytical results of the mode instrument show that the near-field beam intensity distribution of the plane-cone mirror folded cavity laser is uniform.The right-angle-cone mirror folded cavity has the great advantage in the anti-misalignment stability.With the simple structure,it is easy to install and adjust,especially apply to the high power laser system in a bad condition.
For the purpose of simplifying the cavity structure,enhancing the stability especially on the hot stability,enlarging the basic mode volume,improving the beam quality of the high power lasers,a right angle cone mirror laser cavity with a right-angle-cone mirror as the totally reflecting mirror and a parallel flat partially reflecting mirror as the output mirror is introduced.The results of the experiments show that when the misalignment angle of the cone mirror turns to 37.2′,the decrease of the single-pulse output energy of the plane-cone folded cavity laser is less than 5% and the near-field beam patterns have little change;the analytical results of the mode instrument show that the near-field beam intensity distribution of the plane-cone mirror folded cavity laser is uniform.The right-angle-cone mirror folded cavity has the great advantage in the anti-misalignment stability.With the simple structure,it is easy to install and adjust,especially apply to the high power laser system in a bad condition.
2006, 30(4): 412-414.
Abstract:
Spatial carrier phase-shifting method is used to real time holography detection for identifying phase quickly from interferogram.A real time holographic experiment is done on the gas around a heating cord by single exposure method and two types of interferogram are obtained.By using holographic CT technique,the temperature fields are both calculated.The comparison results show that the method is feasible and easy to practical application in real time holographic interferometry.Its accuracy is high.
Spatial carrier phase-shifting method is used to real time holography detection for identifying phase quickly from interferogram.A real time holographic experiment is done on the gas around a heating cord by single exposure method and two types of interferogram are obtained.By using holographic CT technique,the temperature fields are both calculated.The comparison results show that the method is feasible and easy to practical application in real time holographic interferometry.Its accuracy is high.
2006, 30(4): 415-417.
Abstract:
Due to the regular porous nanostructure,porous alumina is always used as templates to prepare the kin of nanomaterials.Therefore,it is very important to investigate the preparation and physical property of porous alumina.Porous alumina was fabricated by anodization in oxalic acid solution.The micro-structures,crystalline state and transmissivity of porous alumina were investigated.By scanning electron microscopy(SEM) observation,distribution of pores was found to be ordered and pores were precisely vertical to their substratum.X-ray diffraction(XRD) demonstrated that the samples were non crystalline structure.In the visible and infrared wavelength range,porous alumina have excellent transmittivty.
Due to the regular porous nanostructure,porous alumina is always used as templates to prepare the kin of nanomaterials.Therefore,it is very important to investigate the preparation and physical property of porous alumina.Porous alumina was fabricated by anodization in oxalic acid solution.The micro-structures,crystalline state and transmissivity of porous alumina were investigated.By scanning electron microscopy(SEM) observation,distribution of pores was found to be ordered and pores were precisely vertical to their substratum.X-ray diffraction(XRD) demonstrated that the samples were non crystalline structure.In the visible and infrared wavelength range,porous alumina have excellent transmittivty.
2006, 30(4): 418-421.
Abstract:
The developing status and major problems of chemical and solid-state lasers are briefly reviewed.Subsequently,the features and mission,the developing plan and status,as well as the major constitutions and key characters of high energy liquid laser area defense system are described and discussed.
The developing status and major problems of chemical and solid-state lasers are briefly reviewed.Subsequently,the features and mission,the developing plan and status,as well as the major constitutions and key characters of high energy liquid laser area defense system are described and discussed.
2006, 30(4): 422-424,428.
Abstract:
In order to study the thermal effect of Nd:GdVO4 crystal in LD end-pumped solid-state laser,a simply method to measure the thermal focal length with stable resonator is presented.By measuring M2 factor and the waist of output beam with CCD beam analyzer,the beam waist of the TEMOO mode can be deduced according to the law of multi-mode Gaussian beam propagation.Based on the ABCD matrix theory of stable resonator,the thermal focal length of the active medium is easily obtained.The experiment shows that the higher the pump power is,the smaller the thermal focal length is,and the worse the thermal effect influent the output beam quality.The thermal focal length of a LD end-pumped Nd:GdVO4 laser is measured and the experimental results agree with the theoretical predication.
In order to study the thermal effect of Nd:GdVO4 crystal in LD end-pumped solid-state laser,a simply method to measure the thermal focal length with stable resonator is presented.By measuring M2 factor and the waist of output beam with CCD beam analyzer,the beam waist of the TEMOO mode can be deduced according to the law of multi-mode Gaussian beam propagation.Based on the ABCD matrix theory of stable resonator,the thermal focal length of the active medium is easily obtained.The experiment shows that the higher the pump power is,the smaller the thermal focal length is,and the worse the thermal effect influent the output beam quality.The thermal focal length of a LD end-pumped Nd:GdVO4 laser is measured and the experimental results agree with the theoretical predication.
2006, 30(4): 425-428.
Abstract:
The laser induced thermal stress forming technique and its development is summarized and its main influencing factors are analyzed.Laser parameters,material properties and workpiece geometry to laser induced thermal stress bending is summed up,its some relations are summarized.In order to make it apply to manufacture,some pivotal existent problems of laser forming technology is put forward based on investigative work of predecessors.Some investigative tasks is pointed out.
The laser induced thermal stress forming technique and its development is summarized and its main influencing factors are analyzed.Laser parameters,material properties and workpiece geometry to laser induced thermal stress bending is summed up,its some relations are summarized.In order to make it apply to manufacture,some pivotal existent problems of laser forming technology is put forward based on investigative work of predecessors.Some investigative tasks is pointed out.
2006, 30(4): 429-431,435.
Abstract:
CASPCM model is proposed to make up the disadvantages of ASPCM model while dealing with faces with large angles.The training samples are grouped according to their distances to model centers and a local ASPCM model is constructed for each group.Synthesis result of CASPCM model is obtained by averaging results of the local ASPCM models with appropriate weights.Gradient-descent algorithm is used to iteratively improve estimate of the head pose.Accuracy and generalization are used to gauge analysis and synthesis abilities of the model.Experimental results show that the two abilities of CASPCM model are both superior to ASPCM model;recognition ratio of CASPCM model is 7% higher than ASPCM model.
CASPCM model is proposed to make up the disadvantages of ASPCM model while dealing with faces with large angles.The training samples are grouped according to their distances to model centers and a local ASPCM model is constructed for each group.Synthesis result of CASPCM model is obtained by averaging results of the local ASPCM models with appropriate weights.Gradient-descent algorithm is used to iteratively improve estimate of the head pose.Accuracy and generalization are used to gauge analysis and synthesis abilities of the model.Experimental results show that the two abilities of CASPCM model are both superior to ASPCM model;recognition ratio of CASPCM model is 7% higher than ASPCM model.
2006, 30(4): 432-435.
Abstract:
Photonic crystal fiber is a highlight of the modern science research.However,in most papers,only qualitative analysis have been carried out theoretically,and there are few practical quantitative calculation.The group velocity-dispersion of photonic crystal fiber(PCF) is studied with plane wave method(PWM) and supercell method.The effective index of the fundamental filling mode and V value are obtained.With obtained effective index,dispersion is calculated using spline interpolation,according to different relative hole size f and different pitch a.Simulation results prove the monochromic property and controlled dispersion property of a photonic crystal fiber.
Photonic crystal fiber is a highlight of the modern science research.However,in most papers,only qualitative analysis have been carried out theoretically,and there are few practical quantitative calculation.The group velocity-dispersion of photonic crystal fiber(PCF) is studied with plane wave method(PWM) and supercell method.The effective index of the fundamental filling mode and V value are obtained.With obtained effective index,dispersion is calculated using spline interpolation,according to different relative hole size f and different pitch a.Simulation results prove the monochromic property and controlled dispersion property of a photonic crystal fiber.
2006, 30(4): 436-437,448.
Abstract:
For detecting elliptically polarized light and partially polarized light,the detection method is analyzed frow the view of the composite retardation plate theory.The results indicate any elliptically polarized light can be compensated to become lineally polarized light throught λ/4 waveplate as long as the fast-axis(slow-axis) of λ/4 wave-plate and the long-axis(short-axis) of elliptically polarized light are in the same orientation,but partially polarized light cann't.Experiments are performanced and the test results accord with theoretical analyses.
For detecting elliptically polarized light and partially polarized light,the detection method is analyzed frow the view of the composite retardation plate theory.The results indicate any elliptically polarized light can be compensated to become lineally polarized light throught λ/4 waveplate as long as the fast-axis(slow-axis) of λ/4 wave-plate and the long-axis(short-axis) of elliptically polarized light are in the same orientation,but partially polarized light cann't.Experiments are performanced and the test results accord with theoretical analyses.
2006, 30(4): 442-444.
Abstract:
For the positive real function image encoded by double random-phase,the first random-phase mask placed in the blank can not serve as the key when the decrypted image is detected by intensity detector in the decrypting process.In connection with the defects,an improved encryption system illuminated with spherical wave is proposed.The input image is not nestled closely to the first random-phase mask,so the first random-phase mask can be used as the key for positive function image and the position of the first random-phase mask provides an additional key.Computer simulation indicates the feasibility of the proposed technique.
For the positive real function image encoded by double random-phase,the first random-phase mask placed in the blank can not serve as the key when the decrypted image is detected by intensity detector in the decrypting process.In connection with the defects,an improved encryption system illuminated with spherical wave is proposed.The input image is not nestled closely to the first random-phase mask,so the first random-phase mask can be used as the key for positive function image and the position of the first random-phase mask provides an additional key.Computer simulation indicates the feasibility of the proposed technique.
2006, 30(4): 445-448.
Abstract:
In order to obtain the nanosecond optical pulse with high power and high repetition frequency,a LD's driver which can produce pulse with nanosecond rise time is designed.The generator is based on the avalanche transistors in a Marx bank circuit.The selection of the avalanche transistors is also described in detail.This driver uses a transistor which has a low avalanche voltage to sharp the trigger pulse,and then use the pulse which is obtained from this transistor to trigger the Marx bank circuit.A large current narrow-pulse for driving the LD can be obtained.This driver can produce a large-amplitude nanosecond pulse and its peak current is up to 12.5A with pulse width of 1.51ns,pulse repetition frequency of 100kHz.It is consequenced that sharping the trigger pulse can reduce the avalanche voltage of the Marx bank circuit and narrow the width of the output pulse.It is more suitable for driving the LD.
In order to obtain the nanosecond optical pulse with high power and high repetition frequency,a LD's driver which can produce pulse with nanosecond rise time is designed.The generator is based on the avalanche transistors in a Marx bank circuit.The selection of the avalanche transistors is also described in detail.This driver uses a transistor which has a low avalanche voltage to sharp the trigger pulse,and then use the pulse which is obtained from this transistor to trigger the Marx bank circuit.A large current narrow-pulse for driving the LD can be obtained.This driver can produce a large-amplitude nanosecond pulse and its peak current is up to 12.5A with pulse width of 1.51ns,pulse repetition frequency of 100kHz.It is consequenced that sharping the trigger pulse can reduce the avalanche voltage of the Marx bank circuit and narrow the width of the output pulse.It is more suitable for driving the LD.
