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RSS2005 Vol. 29, No. 6
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2005, 29(6): 561-564.
[Abstract]
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Abstract:
A temperature field model of laser micro-cladding used to fabricate the conductive lines on insulating boards is established.The formula is induced to show the correlations of conductor linewidth with laser power,laser scanning rates,based on which the linewidths of the conductive lines can be predicted.Experimental results verify that the model is accorded with practical experimental data,which means the model is applicable.
A temperature field model of laser micro-cladding used to fabricate the conductive lines on insulating boards is established.The formula is induced to show the correlations of conductor linewidth with laser power,laser scanning rates,based on which the linewidths of the conductive lines can be predicted.Experimental results verify that the model is accorded with practical experimental data,which means the model is applicable.
2005, 29(6): 565-567,593.
Abstract:
Based on the principle of the double hemicycle diffraction,by giving each of them different discrepancy,the phase can be detected with the diffraction patterns.The experimental results are compared with the simulation results and both of them is consistent,which shows that the method can efficiently obtain the phase information.Sequentially it gives a simple and effective method for accurate phase detection of the segmented mirrors of a huge combined mirror.
Based on the principle of the double hemicycle diffraction,by giving each of them different discrepancy,the phase can be detected with the diffraction patterns.The experimental results are compared with the simulation results and both of them is consistent,which shows that the method can efficiently obtain the phase information.Sequentially it gives a simple and effective method for accurate phase detection of the segmented mirrors of a huge combined mirror.
2005, 29(6): 568-571.
Abstract:
The experiments of laser-clad Fe-based alloy powder doped with and without Nb2O5 on medium carbon steel 45 by powder feeding are carried out.A crack-free,fine and homogeneous Fe-based coating is obtained at a proper amount of Nb2O5-doped under suitable optimizing processing parameters.The effect on microstructure of different amounts of Nb2O5 to Fe-based coating is studied with scanning electron microscopy,optical microscopy and Xray diffraction.The cracking on the surface of the coatings is observed and the hardness in the cross-section of the clad layers is measured.It is reveled that lots and lots of fine dendritic crystal grown along different directions in the cladding layers of G312+0.6% Nb2O5(mass fraction) are uniformly dispersed in the matrix,which is a mixture containing γ(Fe,Ni) solid-solution and chromium carbide or boride.It is considered that the improvement of properties of the coating is due to the following two reasons.On the one hand,Nb atoms can enhance intercrystalline cohesion when they are located in the crystal boundary.On the other hand,particles of NbC,reduced from Nb2O5 by C at high temperature and deposited primarily from the alloy solution,become new crystalline nuclei and increase the nuclear rate in solidification,which leads to the dendritic turn to fine.The cracking susceptibility of the Fe-based coating doped a proper content of Nb2O5 can be reduced because of the decrease in amount of crisp parts in the layers and increase in tenacity of the coatings.
The experiments of laser-clad Fe-based alloy powder doped with and without Nb2O5 on medium carbon steel 45 by powder feeding are carried out.A crack-free,fine and homogeneous Fe-based coating is obtained at a proper amount of Nb2O5-doped under suitable optimizing processing parameters.The effect on microstructure of different amounts of Nb2O5 to Fe-based coating is studied with scanning electron microscopy,optical microscopy and Xray diffraction.The cracking on the surface of the coatings is observed and the hardness in the cross-section of the clad layers is measured.It is reveled that lots and lots of fine dendritic crystal grown along different directions in the cladding layers of G312+0.6% Nb2O5(mass fraction) are uniformly dispersed in the matrix,which is a mixture containing γ(Fe,Ni) solid-solution and chromium carbide or boride.It is considered that the improvement of properties of the coating is due to the following two reasons.On the one hand,Nb atoms can enhance intercrystalline cohesion when they are located in the crystal boundary.On the other hand,particles of NbC,reduced from Nb2O5 by C at high temperature and deposited primarily from the alloy solution,become new crystalline nuclei and increase the nuclear rate in solidification,which leads to the dendritic turn to fine.The cracking susceptibility of the Fe-based coating doped a proper content of Nb2O5 can be reduced because of the decrease in amount of crisp parts in the layers and increase in tenacity of the coatings.
2005, 29(6): 572-574,578.
Abstract:
In the N×M switching nodes,the performance of the share fiber delay lines(FDLs) is compared with that of the no-share FDLs.When the load is 0.7 and the stage number is 24,the packet destroy rate of the share FDLs is 0.1 and that of the no-share FDLs is 10-6.Which shows that the no-share FDLs are more efficient than the share FDLs.
In the N×M switching nodes,the performance of the share fiber delay lines(FDLs) is compared with that of the no-share FDLs.When the load is 0.7 and the stage number is 24,the packet destroy rate of the share FDLs is 0.1 and that of the no-share FDLs is 10-6.Which shows that the no-share FDLs are more efficient than the share FDLs.
2005, 29(6): 575-578.
Abstract:
The current status of nanowires,nanotubes and nanocables synthesized by laser ablation is presented.The synthetic conditions and setup are discussed.The characters and developing trend of quasi-one-dimension nanomaterials synthesized by laser ablation are analyzed.The fine nanoparticles vapored by laser is translated into one-dimension nanomaterials by catalyst at high temperature.The synthetic method of laser ablation is clean,easily controlled and widely applied.
The current status of nanowires,nanotubes and nanocables synthesized by laser ablation is presented.The synthetic conditions and setup are discussed.The characters and developing trend of quasi-one-dimension nanomaterials synthesized by laser ablation are analyzed.The fine nanoparticles vapored by laser is translated into one-dimension nanomaterials by catalyst at high temperature.The synthetic method of laser ablation is clean,easily controlled and widely applied.
2005, 29(6): 579-581.
Abstract:
The human serum polarization fluorescence spectra(SPFS) are excited with 488.0nm Ar-ion laser and collected between 495nm and 640nm both in horizontal and vertical polarization direction respectively.The bandwidth of the SPFS are calculated both in the full width at half maximum and 0.707 bandwidth in intensity.The SPFS from the abnormal are always wider than those from the healthy.However,the difference in the serum fluorescence spectra(SFS) is not obvious.This above result is a valuable reference in the future liver hypohepatia diagnosis.
The human serum polarization fluorescence spectra(SPFS) are excited with 488.0nm Ar-ion laser and collected between 495nm and 640nm both in horizontal and vertical polarization direction respectively.The bandwidth of the SPFS are calculated both in the full width at half maximum and 0.707 bandwidth in intensity.The SPFS from the abnormal are always wider than those from the healthy.However,the difference in the serum fluorescence spectra(SFS) is not obvious.This above result is a valuable reference in the future liver hypohepatia diagnosis.
2005, 29(6): 582-584,588.
Abstract:
In order to reduce the parasitic inductance and resistance of Blumlein circuit,the transmission line capacitor and stored capacitor are designed and manufactured by ourselves,which are substituted by the plate capacitors instead of the old non-inductance capacitor and transmission line.The parasitic inductance of Blumlein circuit decreases once,the pulsed fast discharge power supply works steadily,it is important for diatomic sulfur laser.
In order to reduce the parasitic inductance and resistance of Blumlein circuit,the transmission line capacitor and stored capacitor are designed and manufactured by ourselves,which are substituted by the plate capacitors instead of the old non-inductance capacitor and transmission line.The parasitic inductance of Blumlein circuit decreases once,the pulsed fast discharge power supply works steadily,it is important for diatomic sulfur laser.
2005, 29(6): 585-588.
Abstract:
Based on the Fresnel-Kirchhoff diffraction theory,the focusing property of the one-dimension super-Gaussian beam transmitted through the thin Kerr medium is studied.The simulation for the phase-delay ranging-2rad~2rad is made,and the results show that,for the medium with positive nonlinear refraction index,the Kerr effect of the beam improves the focused intensity,broadens the relative focal shift and reduces the peak intensity on the geometry focal plane;but for negative index medium,it will reduce the focused intensity,however,the other focusing properties remain the same as the positive one.Both conditions can be discussed together,and the influence of the Kerr effect on the focusing property can be reduced by enlarging the beam Fresnel number.
Based on the Fresnel-Kirchhoff diffraction theory,the focusing property of the one-dimension super-Gaussian beam transmitted through the thin Kerr medium is studied.The simulation for the phase-delay ranging-2rad~2rad is made,and the results show that,for the medium with positive nonlinear refraction index,the Kerr effect of the beam improves the focused intensity,broadens the relative focal shift and reduces the peak intensity on the geometry focal plane;but for negative index medium,it will reduce the focused intensity,however,the other focusing properties remain the same as the positive one.Both conditions can be discussed together,and the influence of the Kerr effect on the focusing property can be reduced by enlarging the beam Fresnel number.
2005, 29(6): 589-593.
Abstract:
The characteristics of the Cr4+:YAG laser and single resonant optical parametric oscillator(SRO) pumped intracavity by a passively Q-switched Nd3+:YAG laser are analyzed using Cr4+:YAG as the saturable absorber and laser gain medium.The rate equations describing the dynamic characteristics of this kind of laser and intracavity SRO(ICSRO) are set up.Under suitable conditions,the Cr4+:YAG laser gain medium can amplify the SRO signal wave generated in the second-order nonlinear interacting process if the wavelength of this wave is in the range of the gain spectra of Cr4+:YAG.The influence of intermediate level on the Cr4+:YAG saturable absorber and laser as well as ICSRO are considered in the analysis.This intermediate level between the higher excited state and the upper laser level has a relaxing time constant of approximate 100ns.
The characteristics of the Cr4+:YAG laser and single resonant optical parametric oscillator(SRO) pumped intracavity by a passively Q-switched Nd3+:YAG laser are analyzed using Cr4+:YAG as the saturable absorber and laser gain medium.The rate equations describing the dynamic characteristics of this kind of laser and intracavity SRO(ICSRO) are set up.Under suitable conditions,the Cr4+:YAG laser gain medium can amplify the SRO signal wave generated in the second-order nonlinear interacting process if the wavelength of this wave is in the range of the gain spectra of Cr4+:YAG.The influence of intermediate level on the Cr4+:YAG saturable absorber and laser as well as ICSRO are considered in the analysis.This intermediate level between the higher excited state and the upper laser level has a relaxing time constant of approximate 100ns.
2005, 29(6): 594-595,614.
Abstract:
After quickly remelting Fe73.5Cu1Nb3Si13.5B9 amorphous ribbons by laser,nanocrystalline bulk is gained when tiny melted pools solidified rapidly.The size of nanocrystalline bulk depends on the laser-remelting.When the input laser facula diameter is 20mm~40mm,the output facula diameter is about 2mm and!the scanning speed is 5mm/s,the nanocrystalline bulk can reach up to 2mm and the length and width are not limited.Analysis of its configuration indicates that the main phase in nanocrystalline bulk is α-Fe,the crystal constant of α-FeSi is about 25nm.At the same time,a lot of spherical Nb-rich areas appear.
After quickly remelting Fe73.5Cu1Nb3Si13.5B9 amorphous ribbons by laser,nanocrystalline bulk is gained when tiny melted pools solidified rapidly.The size of nanocrystalline bulk depends on the laser-remelting.When the input laser facula diameter is 20mm~40mm,the output facula diameter is about 2mm and!the scanning speed is 5mm/s,the nanocrystalline bulk can reach up to 2mm and the length and width are not limited.Analysis of its configuration indicates that the main phase in nanocrystalline bulk is α-Fe,the crystal constant of α-FeSi is about 25nm.At the same time,a lot of spherical Nb-rich areas appear.
2005, 29(6): 596-598,651.
Abstract:
The air-clad large-mode-area photonic crystal fibers have more advantages than conventional fibers for application in high power fiber lasers.The research progress of high power PCF lasers is briefly introduced,then the drawbacks existed in the design of coupling system and resonant cavity are analyzed.Finally it is pointed out that PCFs splicing with low loss is the key issue in the further research of higher power fiber lasers.
The air-clad large-mode-area photonic crystal fibers have more advantages than conventional fibers for application in high power fiber lasers.The research progress of high power PCF lasers is briefly introduced,then the drawbacks existed in the design of coupling system and resonant cavity are analyzed.Finally it is pointed out that PCFs splicing with low loss is the key issue in the further research of higher power fiber lasers.
2005, 29(6): 599-600,625.
Abstract:
Growth of Nd:CNGG crystal is reported and its structure,transmission spectrum and laser oscillation properties are described.Employing a 1W laser diode as a pump source,when the pump power is 670mW,the output power of 123.1mW at 1.062μm is obtained with slope efficiency of 22.3%.Nd:CNGG crystal is expected to be a prospective LD-pumping solid-state laser material.
Growth of Nd:CNGG crystal is reported and its structure,transmission spectrum and laser oscillation properties are described.Employing a 1W laser diode as a pump source,when the pump power is 670mW,the output power of 123.1mW at 1.062μm is obtained with slope efficiency of 22.3%.Nd:CNGG crystal is expected to be a prospective LD-pumping solid-state laser material.
2005, 29(6): 601-603,607.
Abstract:
The transmission,reflection and phase properties of anisotropic thin films with columnar microstructures are derived from EM theory.Standard boundary conditions are imposed on resultant electric-field and magnetic-field vectors at interfaces.These matricial relations include multiple reflections while dealing with total fields.Calculation example is presented for a special case of isotropic-biaxial-isotropic system,which should be the foundation of further research and the design of birefringent thin-film device.
The transmission,reflection and phase properties of anisotropic thin films with columnar microstructures are derived from EM theory.Standard boundary conditions are imposed on resultant electric-field and magnetic-field vectors at interfaces.These matricial relations include multiple reflections while dealing with total fields.Calculation example is presented for a special case of isotropic-biaxial-isotropic system,which should be the foundation of further research and the design of birefringent thin-film device.
2005, 29(6): 604-607.
Abstract:
Current fiber-optic pulse replication techniques for generating high-speed optical pulse patterns are studied.The characteristics of different implementation of the fiber-optic pulse replicators based on different techniques are compared according to the different performance requirements of insertion loss,periodicity and power stability of the output pulses in various applications.Through the theoretical analyses of the key parameters of the replicated pulse output from these devices and their limiting factors,the feasibility and methods for further optimization of the output are presented.The optical pulse activecirculating replicator using optical amplifier is suitable for generating a sequence of pulse trains with precise periodicity and high output power.
Current fiber-optic pulse replication techniques for generating high-speed optical pulse patterns are studied.The characteristics of different implementation of the fiber-optic pulse replicators based on different techniques are compared according to the different performance requirements of insertion loss,periodicity and power stability of the output pulses in various applications.Through the theoretical analyses of the key parameters of the replicated pulse output from these devices and their limiting factors,the feasibility and methods for further optimization of the output are presented.The optical pulse activecirculating replicator using optical amplifier is suitable for generating a sequence of pulse trains with precise periodicity and high output power.
2005, 29(6): 608-610.
Abstract:
In order to overcome the limited bandwidth and the weak power of the laser and enlarge the range of the multi-point detection effectively,a tunable fiber laser is designed and used as the source of optical sensor system with WDM and TDM technique.Based on the mode couple theory,using a stepper motor to tune the wavelength of FBG to scan the fiber laser demodulation is analyzed theoretically and studied experimentally.Strain resolution of about 2.9με/step is obtained.The system has high signal-to-noise ratio and can multiplex a large number of FBGs,which is economical and practical in sensor array system.
In order to overcome the limited bandwidth and the weak power of the laser and enlarge the range of the multi-point detection effectively,a tunable fiber laser is designed and used as the source of optical sensor system with WDM and TDM technique.Based on the mode couple theory,using a stepper motor to tune the wavelength of FBG to scan the fiber laser demodulation is analyzed theoretically and studied experimentally.Strain resolution of about 2.9με/step is obtained.The system has high signal-to-noise ratio and can multiplex a large number of FBGs,which is economical and practical in sensor array system.
2005, 29(6): 611-614.
Abstract:
The pressure sensitive characteristic of fiber Bragg gratings is analyzed,the pressure experiments are carried out on different diaphragms.The experimental results indicate that the pressure sensitivity coefficient of fiber Bragg gratings in the FBC20WB2 type diaphragm is much bigger than that in the ZXYC01 type diaphragm.The values are about 376pm/MPa and 45pm/MPa,with measurement precision of 1%(full scale) and 0.5%(full scale) respectively.At the same time there is a very good linearity and repetition between the center wavelength of fiber Bragg grating and pressure change in two diaphragms,and there is scarcely hysteresis effect,their pertinence coefficient is more than 0.9998.The study indicates that the different diaphragm has a great impact on the pressure sensitivity coefficient.
The pressure sensitive characteristic of fiber Bragg gratings is analyzed,the pressure experiments are carried out on different diaphragms.The experimental results indicate that the pressure sensitivity coefficient of fiber Bragg gratings in the FBC20WB2 type diaphragm is much bigger than that in the ZXYC01 type diaphragm.The values are about 376pm/MPa and 45pm/MPa,with measurement precision of 1%(full scale) and 0.5%(full scale) respectively.At the same time there is a very good linearity and repetition between the center wavelength of fiber Bragg grating and pressure change in two diaphragms,and there is scarcely hysteresis effect,their pertinence coefficient is more than 0.9998.The study indicates that the different diaphragm has a great impact on the pressure sensitivity coefficient.
2005, 29(6): 615-616,635.
Abstract:
Dispersion characteristics of fused quartz prism are discribed in detail.The very important conclusion is attained that angle of wavelength span Δθ reduced vie stretching of incidence wavelength λ and increased vie incidence span Δλ,angle A.According to above characteristics,applications of light splitting,computation and identification wavelength,and producing multiple-wavelength laser in LD pump all-solid-state laser are also discussed.
Dispersion characteristics of fused quartz prism are discribed in detail.The very important conclusion is attained that angle of wavelength span Δθ reduced vie stretching of incidence wavelength λ and increased vie incidence span Δλ,angle A.According to above characteristics,applications of light splitting,computation and identification wavelength,and producing multiple-wavelength laser in LD pump all-solid-state laser are also discussed.
2005, 29(6): 617-619,638.
Abstract:
In the view of the particles holography,the resolution and the size of holography film is discussed.The image principle of sensitization about holography film is analyzed.The effect of Gaussian beam distribution and the exposure amount on the recording and reconstruction is studied and the experimental results are obtained.The characteristic curves of three kinds of selected holography film are measured in the same process flow of bathe film.The most suitable exposure of SY-2 film is(180μJ/cm2) for in-line particles holography.
In the view of the particles holography,the resolution and the size of holography film is discussed.The image principle of sensitization about holography film is analyzed.The effect of Gaussian beam distribution and the exposure amount on the recording and reconstruction is studied and the experimental results are obtained.The characteristic curves of three kinds of selected holography film are measured in the same process flow of bathe film.The most suitable exposure of SY-2 film is(180μJ/cm2) for in-line particles holography.
2005, 29(6): 620-622.
Abstract:
A new optical encryption technique based on double random phase computer-generated hologram of asymmetry fractional Fourier transform is presented.In this method,two phase functions are introduced into the input image and its fractional domain spectrum before the fractional Fourier transform hologram of original object of different order in the x and y directions.The transformed result is coded and fabricated into computer-generated hologram.In order to reconstruct the encoded image,two random functions and two orders must be matched.Because the decoding keys are added to four from two,anti-counterfeiting intensity can be improved greatly when it is used to encrypt image or anti-counterfeit.
A new optical encryption technique based on double random phase computer-generated hologram of asymmetry fractional Fourier transform is presented.In this method,two phase functions are introduced into the input image and its fractional domain spectrum before the fractional Fourier transform hologram of original object of different order in the x and y directions.The transformed result is coded and fabricated into computer-generated hologram.In order to reconstruct the encoded image,two random functions and two orders must be matched.Because the decoding keys are added to four from two,anti-counterfeiting intensity can be improved greatly when it is used to encrypt image or anti-counterfeit.
2005, 29(6): 623-625.
Abstract:
A seeded single-cell SBS generator is suggested to achieve high pulse-shape fidelity of SBS to that of the pump.Dependences of SBS pulse shapes on Stokes seed intensity pumped by static field and transient field are experimentally investigated.Pulse-shape fidelity of 90% is obtained.Experimental results show that output Stokes pulses from this SBS geometry are of high pulse-shape fidelity to the pump,which provides the foundation for its further potential application to ICF driver.
A seeded single-cell SBS generator is suggested to achieve high pulse-shape fidelity of SBS to that of the pump.Dependences of SBS pulse shapes on Stokes seed intensity pumped by static field and transient field are experimentally investigated.Pulse-shape fidelity of 90% is obtained.Experimental results show that output Stokes pulses from this SBS geometry are of high pulse-shape fidelity to the pump,which provides the foundation for its further potential application to ICF driver.
2005, 29(6): 626-628,644.
Abstract:
The propeties of overlay in laser shock forming is summarized.Then the impact of its thickness,along with density,light transmittance,impedance,stiffness,content of hydroxide radicalm,anisortropy or isotropy on laser shock forming is analyzed.On the above basis,the ideal property of overlay in laser shock forming is put forward,and a new concept,manufacturing technology of overlay is set forth.In the view of making laser shocking process applicable,more attention showld be paid to the study of manufacturing technology of overlay.
The propeties of overlay in laser shock forming is summarized.Then the impact of its thickness,along with density,light transmittance,impedance,stiffness,content of hydroxide radicalm,anisortropy or isotropy on laser shock forming is analyzed.On the above basis,the ideal property of overlay in laser shock forming is put forward,and a new concept,manufacturing technology of overlay is set forth.In the view of making laser shocking process applicable,more attention showld be paid to the study of manufacturing technology of overlay.
2005, 29(6): 636-638.
Abstract:
Siegman rate equations for passive Q-switch lasers are deeply discussed.In order to fit the emulational application exactly,the original rate equations are improved and applied in the optimal design of such a passive Q-switch laser.
Siegman rate equations for passive Q-switch lasers are deeply discussed.In order to fit the emulational application exactly,the original rate equations are improved and applied in the optimal design of such a passive Q-switch laser.
2005, 29(6): 639-640,648.
Abstract:
Because of the retardation of wave-plate sensitive to the incident angle,a new kind of tunable Lyot filter is designed.The method of tuning is rotating the wave-plate by the axial direction parallel to the optical axis.It is proved that this kind of tunable Lyot filter has the properties of favorable tunability,wide tunable range and so on.
Because of the retardation of wave-plate sensitive to the incident angle,a new kind of tunable Lyot filter is designed.The method of tuning is rotating the wave-plate by the axial direction parallel to the optical axis.It is proved that this kind of tunable Lyot filter has the properties of favorable tunability,wide tunable range and so on.
2005, 29(6): 641-644.
Abstract:
Based on Collins formula,an analytical propagation expression for Hermite-Laguerre-Gaussian(HLG) beams through a paraxial optical ABCD system is derived and used to study their propagation properties in free-space and through a thin lens.The results show that,apart from the mode indices m,n,it is necessary for HLG beams to introduce a new parameter α,which affects their intensity distribution and symmetry property.HLG beams preserve their shape upon propagation.There is a focal shift in HLG beams which is independent of the parameters m,n,and α,which means that HLG beams with different values of m,n,α are focused at the same place.The M2 factor of HLG beams is also given.
Based on Collins formula,an analytical propagation expression for Hermite-Laguerre-Gaussian(HLG) beams through a paraxial optical ABCD system is derived and used to study their propagation properties in free-space and through a thin lens.The results show that,apart from the mode indices m,n,it is necessary for HLG beams to introduce a new parameter α,which affects their intensity distribution and symmetry property.HLG beams preserve their shape upon propagation.There is a focal shift in HLG beams which is independent of the parameters m,n,and α,which means that HLG beams with different values of m,n,α are focused at the same place.The M2 factor of HLG beams is also given.
2005, 29(6): 649-651.
Abstract:
The stress of the Nd:YVO4 and how it affecting the non-linear output of the laser is studied.Experimental results show that the stress birefringence of the crystal can affect the non-linear output of the laser though thestress is very little.How to select high quality laser crystal in order to get steady output is found.
The stress of the Nd:YVO4 and how it affecting the non-linear output of the laser is studied.Experimental results show that the stress birefringence of the crystal can affect the non-linear output of the laser though thestress is very little.How to select high quality laser crystal in order to get steady output is found.
2005, 29(6): 652-653,656.
Abstract:
Through laser damage experiment,the damage threshold of GaN thin film at 10.6μm is reported,i.e.64J/cm2.To improve the quality of GaN thin film,laser treating experiment is investigated by 10.6μm CO2 laser.The results show that the defect density is decreased great after treatment.Finally,treating mechanism is analyzed.
Through laser damage experiment,the damage threshold of GaN thin film at 10.6μm is reported,i.e.64J/cm2.To improve the quality of GaN thin film,laser treating experiment is investigated by 10.6μm CO2 laser.The results show that the defect density is decreased great after treatment.Finally,treating mechanism is analyzed.
2005, 29(6): 654-656.
Abstract:
The focal switch of cosine-Gaussian beams focused by a thin lens without aperture is studied in detail.The third-order equation governing the position of axial maximum intensity and the formula of the relative transition height is derived.A large number of numerical calculation results are presented.It is shown that the focal switch of focused cosine-Gaussian beams can take place as the beam parameter β is larger than 1.
The focal switch of cosine-Gaussian beams focused by a thin lens without aperture is studied in detail.The third-order equation governing the position of axial maximum intensity and the formula of the relative transition height is derived.A large number of numerical calculation results are presented.It is shown that the focal switch of focused cosine-Gaussian beams can take place as the beam parameter β is larger than 1.
2005, 29(6): 657-661.
Abstract:
Several mainstream laser beam combination methods,including stimulated Brillouin scattering,diffraction optics units and all fiber beam combination,are introduced.Comparison and analyses of these methods are presented.Finally an overview about the application of laser beam combination is made.
Several mainstream laser beam combination methods,including stimulated Brillouin scattering,diffraction optics units and all fiber beam combination,are introduced.Comparison and analyses of these methods are presented.Finally an overview about the application of laser beam combination is made.
2005, 29(6): 662-666.
Abstract:
Based on mean field approximation a new method is proposed to solve noisy ICA model,which can fairly well solve over-complete case,and estimate the independent source by restrict the non-negative mixing matrix and the non-negative sources.The experiments have been done for several different cases,such as digital images,simulated face graphics and ORL face database.The digital images and simulated face graphics experiments show the extraction features by the RMFA-ICA are more independent than that of using tradition ICA and unrestrictive MFA-ICA,the ORL face recognition experiments show the recognition ratio by the proposed method is greater than that of using the others methods.
Based on mean field approximation a new method is proposed to solve noisy ICA model,which can fairly well solve over-complete case,and estimate the independent source by restrict the non-negative mixing matrix and the non-negative sources.The experiments have been done for several different cases,such as digital images,simulated face graphics and ORL face database.The digital images and simulated face graphics experiments show the extraction features by the RMFA-ICA are more independent than that of using tradition ICA and unrestrictive MFA-ICA,the ORL face recognition experiments show the recognition ratio by the proposed method is greater than that of using the others methods.
2005, 29(6): 667-669.
Abstract:
The effects of laser mode on the quality of Fe-based alloy laser cladding layers are studied using a multimode CO2 laser and a low order mode CO2 laser respectively.Results show that the appearances of different zones of the multimode laser cladding layers are flatter than those of the low order mode laser cladding layers,especially in the melted zone.The difference of the laser mode also influences the microstructure and the hardness of the cladding layers to some extent.
The effects of laser mode on the quality of Fe-based alloy laser cladding layers are studied using a multimode CO2 laser and a low order mode CO2 laser respectively.Results show that the appearances of different zones of the multimode laser cladding layers are flatter than those of the low order mode laser cladding layers,especially in the melted zone.The difference of the laser mode also influences the microstructure and the hardness of the cladding layers to some extent.
2005, 29(6): 670-672.
Abstract:
TEA CO2 laser pulses,whose wavelength is 10.6μm,are used to remove coatings from SMF28 optical fiber.The relationships between laser fluence,the number of pulses and the ablation depth of optical fiber coatings are investigated.It is shown that the ablation depth of fiber coatings increases with laser fluence in logarithm way and there exists an optimum value in some range to obtain a naked fiber.
TEA CO2 laser pulses,whose wavelength is 10.6μm,are used to remove coatings from SMF28 optical fiber.The relationships between laser fluence,the number of pulses and the ablation depth of optical fiber coatings are investigated.It is shown that the ablation depth of fiber coatings increases with laser fluence in logarithm way and there exists an optimum value in some range to obtain a naked fiber.
2005, 29(6): 629-631.
Abstract:
The factors attributed to the efficiency of the extra-cavity third-harmonic generation are analyzied.The maxium output power of 355nm UV laser is 330mW with the incident pumped power 17W after optimizing the small singal transmittance of the Cr4+:YAG,the transmittance of the output coupler at 1064nm,the focal length of the focusing lens,the nonlinear crystal and aligning the optical elements reasonably.The repetition rates,pusle width,single pulse energy of the pulsed 355nm laser is 28kHz,12ns,12J respectively.The overall light to light efficiency is 2%.
The factors attributed to the efficiency of the extra-cavity third-harmonic generation are analyzied.The maxium output power of 355nm UV laser is 330mW with the incident pumped power 17W after optimizing the small singal transmittance of the Cr4+:YAG,the transmittance of the output coupler at 1064nm,the focal length of the focusing lens,the nonlinear crystal and aligning the optical elements reasonably.The repetition rates,pusle width,single pulse energy of the pulsed 355nm laser is 28kHz,12ns,12J respectively.The overall light to light efficiency is 2%.
2005, 29(6): 632-635.
Abstract:
The MEMS CPW is analyzed,and a novel MEMS designed based on the CPW.The electromagnetism and thermal stress are studied.The parameters of the microscale filter are analyzed,and significant data is obtained for actual MEMS filter.If the design parameters are changed,the different performance of MEMS resonators and filters are obtained.The partial theory and practicality experience of material choice and components design study of wireless communications MEMS devices are provided.
The MEMS CPW is analyzed,and a novel MEMS designed based on the CPW.The electromagnetism and thermal stress are studied.The parameters of the microscale filter are analyzed,and significant data is obtained for actual MEMS filter.If the design parameters are changed,the different performance of MEMS resonators and filters are obtained.The partial theory and practicality experience of material choice and components design study of wireless communications MEMS devices are provided.
2005, 29(6): 645-648.
Abstract:
In order to get the optimal wavelength pairs for twocolor satellite laser ranging,with the factors including atmosphere effect,the response of the receiver and the laser considered,beginning with the precision of atmosphere correction,based on the lidar equation,the wavelength figure of merit,which can determine whether the pair is selected properly,is obtained.Various figure of merits of the wavelength pairs induced by the technology of harmony and Raman scattering is calculated,the possible wavelength pairs are discussed.Finally the standard and basis for the selection of optimal wavelengths is set up.
In order to get the optimal wavelength pairs for twocolor satellite laser ranging,with the factors including atmosphere effect,the response of the receiver and the laser considered,beginning with the precision of atmosphere correction,based on the lidar equation,the wavelength figure of merit,which can determine whether the pair is selected properly,is obtained.Various figure of merits of the wavelength pairs induced by the technology of harmony and Raman scattering is calculated,the possible wavelength pairs are discussed.Finally the standard and basis for the selection of optimal wavelengths is set up.
