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RSS2006 Vol. 30, No. 3
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2006, 30(3): 225-227,231.
[Abstract]
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Abstract:
For the purpose of choosing correct parameter in future experiments,numerical analysis of the transient-state of the Yb3+-doped double clad fiber laser used in the master-oscillator power amplifier(MOPA) system has been preformed.The pump power density distribution and reverse population density distribution,the effect of the fiber length and input light pulse energy on the output power have been analyzed.These results are benefit for the design of MOPA's parameters such as fiber length,pump power and master-oscillator's power in experiment.
For the purpose of choosing correct parameter in future experiments,numerical analysis of the transient-state of the Yb3+-doped double clad fiber laser used in the master-oscillator power amplifier(MOPA) system has been preformed.The pump power density distribution and reverse population density distribution,the effect of the fiber length and input light pulse energy on the output power have been analyzed.These results are benefit for the design of MOPA's parameters such as fiber length,pump power and master-oscillator's power in experiment.
2006, 30(3): 228-231.
Abstract:
The microstructure and properties of laser clad coating are introduced after adding nano particles.Nickel-based alloy powder with different addition of nano-CeO2 is laser cladded onto Q235 steel substrate.The coating is examined to reveal the microstructure,phase composition,microhardness and wear resistance using optical microscope(OP),X-ray diffractometer(XRD),microhardness tester,block-on-ring wear tester and scanning electron microscope(SEM) respectively.The results show that fine dendrite and equiaxed dendrite are observed by adding nano-CeO2.Equiaxed dendrite across the section is obtained when the additive reaches to 1.5%(mass fraction).A new phase(Ce2Ni21B6) is found.The microhardness and wear resistance of the coating are much higher than those of the substrate,and further improved by adding nano-CeO2.But the hardness decreased when the additive amount is much high.The mechanism of these effects is also discussed.
The microstructure and properties of laser clad coating are introduced after adding nano particles.Nickel-based alloy powder with different addition of nano-CeO2 is laser cladded onto Q235 steel substrate.The coating is examined to reveal the microstructure,phase composition,microhardness and wear resistance using optical microscope(OP),X-ray diffractometer(XRD),microhardness tester,block-on-ring wear tester and scanning electron microscope(SEM) respectively.The results show that fine dendrite and equiaxed dendrite are observed by adding nano-CeO2.Equiaxed dendrite across the section is obtained when the additive reaches to 1.5%(mass fraction).A new phase(Ce2Ni21B6) is found.The microhardness and wear resistance of the coating are much higher than those of the substrate,and further improved by adding nano-CeO2.But the hardness decreased when the additive amount is much high.The mechanism of these effects is also discussed.
2006, 30(3): 232-234,240.
Abstract:
Micropulse lidar(MPL) is a new type of lidar system.The error analysis and simulation for backscattering ratio and backscattering coefficients of aerosol detected by MPL are presented.The error source and uncertainty have been analyzed.A methodology is put forward for objective and automatic determination of the uncertainty in MPL aerosol measurements.Effects of probable error on the backscattering ratio and backscattering coefficients of aerosol have been discussed and analyzed in detail.The reliable theory is provided for improving the measurement accuracy of MPL.
Micropulse lidar(MPL) is a new type of lidar system.The error analysis and simulation for backscattering ratio and backscattering coefficients of aerosol detected by MPL are presented.The error source and uncertainty have been analyzed.A methodology is put forward for objective and automatic determination of the uncertainty in MPL aerosol measurements.Effects of probable error on the backscattering ratio and backscattering coefficients of aerosol have been discussed and analyzed in detail.The reliable theory is provided for improving the measurement accuracy of MPL.
2006, 30(3): 235-237.
Abstract:
To solve some problems of silicon etching technique,laser electrochemical etching process,which combines laser direct etching process and electrochemical etching process,is adopted to etch silicon.The characteristic of compound etching technique is investigated.The experiments of micromachining silicon by laser-induced electrochemical etching are carried out with a 248nm KrF excimer laser as light source and KOH solution as electrolyte.Based on the experimental results,basic etching silicon appearances by laser electrochemical etching are researched and the quality problems of transverse effect on etching surface and impacting effect on back surface are analyzed.The quality and verticality of cavities by the techniques are good.At the same time,the etching stop of silicon anisotropic etching in alkaline solution is raveled in the process.As a result,it possesses the ability of machining big aspect ratio microstructure.Besides,this process can transfer pattern without mask.
To solve some problems of silicon etching technique,laser electrochemical etching process,which combines laser direct etching process and electrochemical etching process,is adopted to etch silicon.The characteristic of compound etching technique is investigated.The experiments of micromachining silicon by laser-induced electrochemical etching are carried out with a 248nm KrF excimer laser as light source and KOH solution as electrolyte.Based on the experimental results,basic etching silicon appearances by laser electrochemical etching are researched and the quality problems of transverse effect on etching surface and impacting effect on back surface are analyzed.The quality and verticality of cavities by the techniques are good.At the same time,the etching stop of silicon anisotropic etching in alkaline solution is raveled in the process.As a result,it possesses the ability of machining big aspect ratio microstructure.Besides,this process can transfer pattern without mask.
2006, 30(3): 238-240.
Abstract:
The developing tendency of the electro-optical countering systems are pointed out,which can practise the countermeasure with the multi-administrative levels to feature gaining the initiative by striking first in place of the passive defence.The current developing trends of the integrative technique and some developing programs of the partial techniques which are in demand on the electro-optical countermeasure are also described.
The developing tendency of the electro-optical countering systems are pointed out,which can practise the countermeasure with the multi-administrative levels to feature gaining the initiative by striking first in place of the passive defence.The current developing trends of the integrative technique and some developing programs of the partial techniques which are in demand on the electro-optical countermeasure are also described.
2006, 30(3): 241-243,273.
Abstract:
Free running laser of hydrothermally grown emerald crystal Crdoped Be3Al2Si6O18 is reported.With the use of 670.7nm red laser by intracavity-doubling of Nd∶YAlO3/LBO 1.3414μm wavelength and symmetrical confocal resonator,732nm laser of emerald is produced with 46μW laser output when the incident power was 2.89W.The laser threshold value of emerald crystal is estimated between 0.5W and 0.6W.
Free running laser of hydrothermally grown emerald crystal Crdoped Be3Al2Si6O18 is reported.With the use of 670.7nm red laser by intracavity-doubling of Nd∶YAlO3/LBO 1.3414μm wavelength and symmetrical confocal resonator,732nm laser of emerald is produced with 46μW laser output when the incident power was 2.89W.The laser threshold value of emerald crystal is estimated between 0.5W and 0.6W.
2006, 30(3): 244-247.
Abstract:
In order to improve diamond fine powder sinter's mechanical property,using the present laser technique,high power transverse CO2 laser is used to sinter diamond fine powder compact to study the integrating capability in the sinter between diamond fine powder and metallic powder,microstructure and the forming mechanism of microstructure in the different laser technical parameters.The results show that the fine sintering will be gained in the reasonable laser technical parameter,which can improve densenses and wear resistance,inaugurate a new technique of manufacture diamond tools.
In order to improve diamond fine powder sinter's mechanical property,using the present laser technique,high power transverse CO2 laser is used to sinter diamond fine powder compact to study the integrating capability in the sinter between diamond fine powder and metallic powder,microstructure and the forming mechanism of microstructure in the different laser technical parameters.The results show that the fine sintering will be gained in the reasonable laser technical parameter,which can improve densenses and wear resistance,inaugurate a new technique of manufacture diamond tools.
2006, 30(3): 248-251.
Abstract:
An optical-thermal model in cylindrical coordinate of pulsed laser scribing multi-layer thin film solar cell module is established.Monte Carlo method is employed to obtain the light fluencies rate of multi-layer material.Finite element method(FEM) is used to solve the heat equation in cylindrical coordinate.And the connection of the laser energy density,repeatition frequency,the shape of pulse and facula,scribing rate and scribing quality is obtained.
An optical-thermal model in cylindrical coordinate of pulsed laser scribing multi-layer thin film solar cell module is established.Monte Carlo method is employed to obtain the light fluencies rate of multi-layer material.Finite element method(FEM) is used to solve the heat equation in cylindrical coordinate.And the connection of the laser energy density,repeatition frequency,the shape of pulse and facula,scribing rate and scribing quality is obtained.
2006, 30(3): 252-254.
Abstract:
Based on light-waveguide and matrix theory,the theoretical light transmission model is set up to analyse the hollow-core Bragg fiber.The unequal-period Bragg fiber structure is simulated in order to get the minimum out-flowing flux.The fiber with eight cladding-layers is obtained through optimum design,and its loss characteristic is analyzed.This simple structure is very useful for the fabrication and application of Bragg fiber due to its low loss and small number of cladding layers.
Based on light-waveguide and matrix theory,the theoretical light transmission model is set up to analyse the hollow-core Bragg fiber.The unequal-period Bragg fiber structure is simulated in order to get the minimum out-flowing flux.The fiber with eight cladding-layers is obtained through optimum design,and its loss characteristic is analyzed.This simple structure is very useful for the fabrication and application of Bragg fiber due to its low loss and small number of cladding layers.
2006, 30(3): 255-257,261.
Abstract:
Technology scheme decision is a complex process for a real laser product.Usually,qualitative analysis and logical judgement are used in this process.It's difficult to analyze in quantitive way.With high power crosscurrent CO2 laser as an example,analysis of hiberarchy process(AHP) is used for decision process between physical prototype(PP) and virtual prototype(VP) in a quantitive way.Through analyzing mearusures,criterias and target in hiberarchy,the quantitive comparative relation between PP and VP in criteria layer and target layer are obtained and it is used to make shceme decision.Results show that it's better for laser development with PP than VP.
Technology scheme decision is a complex process for a real laser product.Usually,qualitative analysis and logical judgement are used in this process.It's difficult to analyze in quantitive way.With high power crosscurrent CO2 laser as an example,analysis of hiberarchy process(AHP) is used for decision process between physical prototype(PP) and virtual prototype(VP) in a quantitive way.Through analyzing mearusures,criterias and target in hiberarchy,the quantitive comparative relation between PP and VP in criteria layer and target layer are obtained and it is used to make shceme decision.Results show that it's better for laser development with PP than VP.
2006, 30(3): 258-261.
Abstract:
The breaking surface and dispersing fragments bring some difficulties to the surface restoration of dynamic process including impact or explosion process.Therefore,a novel method of 3-D restoration for the breaking surface of dynamic process based on FTP is proposed.3-D binary masks are built with the information of the cracks of the deformed fringes images,and the 3-D phase maps are unwrapped under the control of the masks.The experiment of the 3-D surface shape restoration of a breaking glass proved the feasibility of this method,and this method provides a new means for thoroughly analyzing the theory of dynamic process such as dispersing fragments,deformation of material,explosion process and deformation in impact.
The breaking surface and dispersing fragments bring some difficulties to the surface restoration of dynamic process including impact or explosion process.Therefore,a novel method of 3-D restoration for the breaking surface of dynamic process based on FTP is proposed.3-D binary masks are built with the information of the cracks of the deformed fringes images,and the 3-D phase maps are unwrapped under the control of the masks.The experiment of the 3-D surface shape restoration of a breaking glass proved the feasibility of this method,and this method provides a new means for thoroughly analyzing the theory of dynamic process such as dispersing fragments,deformation of material,explosion process and deformation in impact.
2006, 30(3): 262-264,270.
Abstract:
In order to study cracking problem in multitrack laser-clad coating,model and method to measure the residual stress distributed along depth of laser-clad coating are established.Residual stress in the upper layer of multitrack overlapping laser-clad WF218 Nickle-based coating presents as tensile stress,while in the transition zone between coating and substrate,the residual stress presents as compressive stress.Test results show that this technique is helpful to characterize the residual stress distribution in laser-clad coating.
In order to study cracking problem in multitrack laser-clad coating,model and method to measure the residual stress distributed along depth of laser-clad coating are established.Residual stress in the upper layer of multitrack overlapping laser-clad WF218 Nickle-based coating presents as tensile stress,while in the transition zone between coating and substrate,the residual stress presents as compressive stress.Test results show that this technique is helpful to characterize the residual stress distribution in laser-clad coating.
2006, 30(3): 265-267,310.
Abstract:
Bulk aluminium material is chosen as targets to prepare pure Al film by the method of pulsed laser deposition(PLD).The thickness uniformity of Al film in coaxial and side-axial deposition modes is also studied comparatively.Besides,the effects of substrate temperature,laser power and repetition rate on deposition rate of Al film in side-axial deposition mode are investigated respectively.The results show that the thickness uniformity of the film gotten in side-axial deposition mode is better than that in coaxial deposition mode.The deposition rate of Al film decreases with the increase of the substrate temperature.However,the deposition rate of Al film increases with increasing laser power.Especially,there is a maximum deposition rate of Al film by varying the laser repetition rate.The above method and results can be used as a theoretical guidance for big area film deposition by PLD in application.
Bulk aluminium material is chosen as targets to prepare pure Al film by the method of pulsed laser deposition(PLD).The thickness uniformity of Al film in coaxial and side-axial deposition modes is also studied comparatively.Besides,the effects of substrate temperature,laser power and repetition rate on deposition rate of Al film in side-axial deposition mode are investigated respectively.The results show that the thickness uniformity of the film gotten in side-axial deposition mode is better than that in coaxial deposition mode.The deposition rate of Al film decreases with the increase of the substrate temperature.However,the deposition rate of Al film increases with increasing laser power.Especially,there is a maximum deposition rate of Al film by varying the laser repetition rate.The above method and results can be used as a theoretical guidance for big area film deposition by PLD in application.
2006, 30(3): 268-270.
Abstract:
In order to study thermal effects of high power double clad fiber laser,the thermal distribution of Yb3+-doped double clad fiber laser is derived and calculated.It is shown that absorption coefficient and clad radius of fiber,heat transfer coefficient and pumping method can affect temperature distribution.Conclusions are useful for designing kW level fiber lasers.
In order to study thermal effects of high power double clad fiber laser,the thermal distribution of Yb3+-doped double clad fiber laser is derived and calculated.It is shown that absorption coefficient and clad radius of fiber,heat transfer coefficient and pumping method can affect temperature distribution.Conclusions are useful for designing kW level fiber lasers.
2006, 30(3): 271-273.
Abstract:
The superiority of the connection of nut with protection by laser welding is expounded.The method of laser welding is used to study the organize and performance of Q235 steel and H62 brass protective nut connected by laser welding respectively.Test results show that the formation of protective nut by laser welding have narrow heat affect zone and minimum organization grow up inclination,gentle hardness gradient,and the protective cover is nearly not out of shape
The superiority of the connection of nut with protection by laser welding is expounded.The method of laser welding is used to study the organize and performance of Q235 steel and H62 brass protective nut connected by laser welding respectively.Test results show that the formation of protective nut by laser welding have narrow heat affect zone and minimum organization grow up inclination,gentle hardness gradient,and the protective cover is nearly not out of shape
2006, 30(3): 274-276.
Abstract:
The method of correcting the retardation deviation of a wave-plate through geometrical optics is studied.By means of exploring the relation of the orientation of incident light and the change of retardation of the crystal device,the formula for calculating the change of retardation of a wave-plate is derived when the incident light is oblique incident.Thus the retardation deviation can be corrected through rotating the wave-plate on the axis direction parallel to the optical axis or the axis direction vertical to the optical axis.The retardation of a λ/2 wave-plate and a λ/4 wave-plate is corrected by means of light extinction method and light minimum method respectively.Thus the deviation of retardation of wave-plate can be corrected by means of rotating.
The method of correcting the retardation deviation of a wave-plate through geometrical optics is studied.By means of exploring the relation of the orientation of incident light and the change of retardation of the crystal device,the formula for calculating the change of retardation of a wave-plate is derived when the incident light is oblique incident.Thus the retardation deviation can be corrected through rotating the wave-plate on the axis direction parallel to the optical axis or the axis direction vertical to the optical axis.The retardation of a λ/2 wave-plate and a λ/4 wave-plate is corrected by means of light extinction method and light minimum method respectively.Thus the deviation of retardation of wave-plate can be corrected by means of rotating.
2006, 30(3): 277-279.
Abstract:
It is necessary to detect the atmospheric scattering laser in some situation.Based on the atmospheric model of cities and suburbs,the distribution of the scattering irradiance of 1.06μm laser in the low atmosphere is analyzed and calculated by using Mie's scattering theory.The characteristics of the scattering irradiance distribution are obtained,which are proofed in part.That is,the maximum intensity of aerial scattering laser decreases slowly with the off-axial distance and is inversely proportional to the distance;visibility only affects scattering intensity,instead of the distribution of scattering intensity.The characteristics can provide the theoretical basis and reference for the signal detection of laser scattering.
It is necessary to detect the atmospheric scattering laser in some situation.Based on the atmospheric model of cities and suburbs,the distribution of the scattering irradiance of 1.06μm laser in the low atmosphere is analyzed and calculated by using Mie's scattering theory.The characteristics of the scattering irradiance distribution are obtained,which are proofed in part.That is,the maximum intensity of aerial scattering laser decreases slowly with the off-axial distance and is inversely proportional to the distance;visibility only affects scattering intensity,instead of the distribution of scattering intensity.The characteristics can provide the theoretical basis and reference for the signal detection of laser scattering.
2006, 30(3): 280-282.
Abstract:
Based on Jones matrix,the property of twisted nematic liquid crystal(TNLC) is studied.It is found that TNLC modulated by voltage is equivalent to λ/2 wave-plate with proper thickness.Furthermore combination TNLC with two λ/4 wave-plate can be equivalent to achromatic λ/4 or λ/2 wave-plate wholly when the voltage is higher than liminal voltage,or it can be used as a common 90° rotationer when the voltage is removed.
Based on Jones matrix,the property of twisted nematic liquid crystal(TNLC) is studied.It is found that TNLC modulated by voltage is equivalent to λ/2 wave-plate with proper thickness.Furthermore combination TNLC with two λ/4 wave-plate can be equivalent to achromatic λ/4 or λ/2 wave-plate wholly when the voltage is higher than liminal voltage,or it can be used as a common 90° rotationer when the voltage is removed.
2006, 30(3): 283-285.
Abstract:
After analyzing the noise in light path,circuit and signal process in the system of optical monitor,the frequency-stabilized chopper,low noise receiving circuit and digital lock-in amplifier with excellent performance of noise restraint are designed.Thereby the precision and stability of the system is improved greatly.Applying the system in optical coating system,the optical monitor shows high precision and stability.
After analyzing the noise in light path,circuit and signal process in the system of optical monitor,the frequency-stabilized chopper,low noise receiving circuit and digital lock-in amplifier with excellent performance of noise restraint are designed.Thereby the precision and stability of the system is improved greatly.Applying the system in optical coating system,the optical monitor shows high precision and stability.
2006, 30(3): 286-288.
Abstract:
In order to exploit the 1.44μm laser with unique merits in medical application,the multi-mirror technology of(Nd∶YAG) laser is adopt.The mirrors with special coating parameters to different wavelength are designed.By the means of adding the mirrors,the loss of 1.06μm,1.32μm as well as the gain parameter of 1.44μm are increased in resonator.Then the difficult problems of coating requests in two-mirror cavity are solved.The laser oscillation of 1.06μm and 1.32μm has been restricted effectually.Eventually,the transition from 4F(3/2) to 4I(15/2) levels is realized,and the 1.44μm laser is achieved.Theoretic analysis and experimental design show that 1.44μm laser oscillates easier in multi-wave resonator than in two-mirror resonator.
In order to exploit the 1.44μm laser with unique merits in medical application,the multi-mirror technology of(Nd∶YAG) laser is adopt.The mirrors with special coating parameters to different wavelength are designed.By the means of adding the mirrors,the loss of 1.06μm,1.32μm as well as the gain parameter of 1.44μm are increased in resonator.Then the difficult problems of coating requests in two-mirror cavity are solved.The laser oscillation of 1.06μm and 1.32μm has been restricted effectually.Eventually,the transition from 4F(3/2) to 4I(15/2) levels is realized,and the 1.44μm laser is achieved.Theoretic analysis and experimental design show that 1.44μm laser oscillates easier in multi-wave resonator than in two-mirror resonator.
2006, 30(3): 289-291.
Abstract:
In order to achieve special center wavelength in mode-locked fiber lasers,the experimental study of wavelength-tunable Yb3+doped fiber lasers using the nonlinear optical loop mirror(NOLM) for mode-locked operating is reported.The fiber laser is self-starting easily and the operating center wavelength can be tuned from 1030nm to 1081nm.The fiber laser can generate 2.05mW average power of 234.375ps pulse duration at a repetition rate of 3.842MHz when the operating center wavelength is 1053nm and spectrum width is about 6nm.The self-starting of the mode-locked fiber laser can be achieved easily,and the mode-locked operation can be hardly influenced by the environment disturbance in days.It can produce the special center wavelength,and is to be applied in science and engineering as a center wavelength-tunable mode-locked fiber laser.
In order to achieve special center wavelength in mode-locked fiber lasers,the experimental study of wavelength-tunable Yb3+doped fiber lasers using the nonlinear optical loop mirror(NOLM) for mode-locked operating is reported.The fiber laser is self-starting easily and the operating center wavelength can be tuned from 1030nm to 1081nm.The fiber laser can generate 2.05mW average power of 234.375ps pulse duration at a repetition rate of 3.842MHz when the operating center wavelength is 1053nm and spectrum width is about 6nm.The self-starting of the mode-locked fiber laser can be achieved easily,and the mode-locked operation can be hardly influenced by the environment disturbance in days.It can produce the special center wavelength,and is to be applied in science and engineering as a center wavelength-tunable mode-locked fiber laser.
2006, 30(3): 292-294.
Abstract:
According to the influence of each laser parameter on processing and the advantage that a laser can achieve high laser quality nearby the last threshold,AOM Q-switched Nd∶YAG pulsed laser is adopted for microdrilling.As a result,the 15μm microhole in 0.7mm-thick zincification plate steel is obtained,and the ratio of depth and width is over 50,100% drilling rate is acquired.This method can achicve high quality laser microdrilling based on experiment.
According to the influence of each laser parameter on processing and the advantage that a laser can achieve high laser quality nearby the last threshold,AOM Q-switched Nd∶YAG pulsed laser is adopted for microdrilling.As a result,the 15μm microhole in 0.7mm-thick zincification plate steel is obtained,and the ratio of depth and width is over 50,100% drilling rate is acquired.This method can achicve high quality laser microdrilling based on experiment.
2006, 30(3): 295-297.
Abstract:
The traditional operating method of LD power driver is that the user preset the parameters of drive current such as the rate,pulse width and amplitude.The LD cannot adjust its working parameters according to the variation of its environment with this method.A new tempreture adaptively adjustable driver for high power laser is proposed,which can detect the tempreture variation of the LD and adjust its drive current according to the detected temperature.With this method the LD can work steadily in broader range of temperature.
The traditional operating method of LD power driver is that the user preset the parameters of drive current such as the rate,pulse width and amplitude.The LD cannot adjust its working parameters according to the variation of its environment with this method.A new tempreture adaptively adjustable driver for high power laser is proposed,which can detect the tempreture variation of the LD and adjust its drive current according to the detected temperature.With this method the LD can work steadily in broader range of temperature.
2006, 30(3): 298-300.
Abstract:
In order to improve the guidance method for torpedoes,based on laser Doppler effect,a theoretical model is established for detecting the ship wake with laser.A differential optical system is designed to produce Doppler shift frequency in scattering signal on sensor,which can improve the signal-to-noise ratio efficiently.The simulation results indicate that the Doppler shift signal can be detected by lock-in amplifier technique,and the noise will be limited.The technique has a broad applicative perspective in under-water weaponry.
In order to improve the guidance method for torpedoes,based on laser Doppler effect,a theoretical model is established for detecting the ship wake with laser.A differential optical system is designed to produce Doppler shift frequency in scattering signal on sensor,which can improve the signal-to-noise ratio efficiently.The simulation results indicate that the Doppler shift signal can be detected by lock-in amplifier technique,and the noise will be limited.The technique has a broad applicative perspective in under-water weaponry.
2006, 30(3): 301-303.
Abstract:
Based on the interference signal in the micro-photoluminescence(μ-PL) spectra,a practical method of getting local optical thickness for GaN-based material is presented.By means of analyzing the sequence energy of interference peaks,the optical thickness of the GaN-based films can be determined.The non-uniformity of the fitted parameter can correspondingly show that of the optical thickness.This can give the important information for optimizing the material growth technique.
Based on the interference signal in the micro-photoluminescence(μ-PL) spectra,a practical method of getting local optical thickness for GaN-based material is presented.By means of analyzing the sequence energy of interference peaks,the optical thickness of the GaN-based films can be determined.The non-uniformity of the fitted parameter can correspondingly show that of the optical thickness.This can give the important information for optimizing the material growth technique.
2006, 30(3): 304-307.
Abstract:
Based on the fact the optical field distribution of the transmitted beams of a multi-mode fiber can be treated as Gaussian distribution,the optical fields of a fiber bundle made up of multi-mode fibers are incoherent.The intensity distribution of a fiber bundle coupling LD output beams transmitting space coupling system is numerically simulated and experimentally studied.The simulation results are in good agreement with the experimental ones.Both of them show that for a thin convex lens,the maximum intensity value and the minimum beam size are obtained in the focal plane,and that with the increase of the focal length,the beam size increase linearly and center intensity decrease dramatically in the focal plane.
Based on the fact the optical field distribution of the transmitted beams of a multi-mode fiber can be treated as Gaussian distribution,the optical fields of a fiber bundle made up of multi-mode fibers are incoherent.The intensity distribution of a fiber bundle coupling LD output beams transmitting space coupling system is numerically simulated and experimentally studied.The simulation results are in good agreement with the experimental ones.Both of them show that for a thin convex lens,the maximum intensity value and the minimum beam size are obtained in the focal plane,and that with the increase of the focal length,the beam size increase linearly and center intensity decrease dramatically in the focal plane.
2006, 30(3): 308-310.
Abstract:
Dynamic laser drilling in the sticking plaster is being applied on the product line so that the traditional means is replaced.The method makes group-drilling into reality by means of gearing and dynamic emending.Dynamic emending includes speed emending and galvanometer scanning emending.The size and shape of the holes and distance between holes can be adjusted under 1m/min~8m/min by the control system.
Dynamic laser drilling in the sticking plaster is being applied on the product line so that the traditional means is replaced.The method makes group-drilling into reality by means of gearing and dynamic emending.Dynamic emending includes speed emending and galvanometer scanning emending.The size and shape of the holes and distance between holes can be adjusted under 1m/min~8m/min by the control system.
2006, 30(3): 311-312,316.
Abstract:
In order to save the rare iceland and increase the shear difference,a new type of parallel beam splitter combined of iceland and glass is designed.The prism is made of ZBaF3 glass,between which is iceland.The glue is C10H7Br with high refractive index.It can be approved by the theory and experiment that the extinction ratio of the parallel beam splitter is better than 10-3,and the shear difference is improved too.
In order to save the rare iceland and increase the shear difference,a new type of parallel beam splitter combined of iceland and glass is designed.The prism is made of ZBaF3 glass,between which is iceland.The glue is C10H7Br with high refractive index.It can be approved by the theory and experiment that the extinction ratio of the parallel beam splitter is better than 10-3,and the shear difference is improved too.
2006, 30(3): 313-316.
Abstract:
To improve the productivity of fabrication of the narrow band DWDM film filter,the monitoring method and error in coating this film is discussed.Monte Carlo method is used to model the tolerance of the layer for the filter,and the results are used to select the easy coating film system.The film thickness error of each layer is obtained by calculating the Macleod maximum sensitivity.The compensation of the film thickness between each layer is obtained by modeling the optical monitoring processes and the film admittance.The strategy of controlling the film thickness is obtained through the above measures,and the experiments have proved that this is crucial to coating the film for the filter and impoving the productivity.
To improve the productivity of fabrication of the narrow band DWDM film filter,the monitoring method and error in coating this film is discussed.Monte Carlo method is used to model the tolerance of the layer for the filter,and the results are used to select the easy coating film system.The film thickness error of each layer is obtained by calculating the Macleod maximum sensitivity.The compensation of the film thickness between each layer is obtained by modeling the optical monitoring processes and the film admittance.The strategy of controlling the film thickness is obtained through the above measures,and the experiments have proved that this is crucial to coating the film for the filter and impoving the productivity.
2006, 30(3): 317-319.
Abstract:
A laser generation and optical difference detection method of surface acoustic waves(SAW) is used to study the influence of laser source on SAW.SAW are excited employing a Nd∶YAG laser on sample aluminum plate and detected with an optical difference detection system based on optical beam deflection technique with a 632nm He-Ne laser.The experimental investigation of the influence of the type of laser source and line source energy on laser generated SAW is carried out.Furthermore,the generation of SAW is discussed from the principles of thermoelasticity and ablation.In these two principles,the amplitude of SAW takes a great change.With the increase of the incident power density,the amplitude of SAW changes from linear to nonlinear.These results provide powerful guidance for the theory research of laser generated SAW.
A laser generation and optical difference detection method of surface acoustic waves(SAW) is used to study the influence of laser source on SAW.SAW are excited employing a Nd∶YAG laser on sample aluminum plate and detected with an optical difference detection system based on optical beam deflection technique with a 632nm He-Ne laser.The experimental investigation of the influence of the type of laser source and line source energy on laser generated SAW is carried out.Furthermore,the generation of SAW is discussed from the principles of thermoelasticity and ablation.In these two principles,the amplitude of SAW takes a great change.With the increase of the incident power density,the amplitude of SAW changes from linear to nonlinear.These results provide powerful guidance for the theory research of laser generated SAW.
2006, 30(3): 320-322,326.
Abstract:
The large-size narrow-band 1064nm filters with high performance are developed with Ta2O5/SiO2 oxide hard film material using some unique techniques in optical communication dense wavelength division multiplex(DWDM).The results of the film design,trial production and the performance are presented.All the results prove that the filters reach,even exceed the requirements of clients.Now the filters are fabricated in a batch production.
The large-size narrow-band 1064nm filters with high performance are developed with Ta2O5/SiO2 oxide hard film material using some unique techniques in optical communication dense wavelength division multiplex(DWDM).The results of the film design,trial production and the performance are presented.All the results prove that the filters reach,even exceed the requirements of clients.Now the filters are fabricated in a batch production.
2006, 30(3): 323-326.
Abstract:
The couple equations with plan wave have been improved to describe focused Gaussian beam under big signal.With the improved equations,the SHG character of LBO has been analyzed under the condition of broad emission spectra of Yb-doped fiber laser.Main results are summarized as follows:in the case of all the emission spectra of Yb-doped,none critical phase match(NCPM) can be reached by temperature tuning.With increasing of wave length of fundamental beam,the SHG efficiency decreases a little,the acceptable temperature and the acceptable wavelength increase greatly,the acceptable angle increases not so obviously.It shows that an ideal SHG result can bring about using none critical phase match and long fundamental wavelength.
The couple equations with plan wave have been improved to describe focused Gaussian beam under big signal.With the improved equations,the SHG character of LBO has been analyzed under the condition of broad emission spectra of Yb-doped fiber laser.Main results are summarized as follows:in the case of all the emission spectra of Yb-doped,none critical phase match(NCPM) can be reached by temperature tuning.With increasing of wave length of fundamental beam,the SHG efficiency decreases a little,the acceptable temperature and the acceptable wavelength increase greatly,the acceptable angle increases not so obviously.It shows that an ideal SHG result can bring about using none critical phase match and long fundamental wavelength.
2006, 30(3): 329-331.
Abstract:
Erbium glass lasers can directly output 1.54μm eye-safe laser and can be used in eye-safe rangefinding applications.LD bar side-pumped Er+3,Yb+3 phosphate glass laser is reported.At free-running mode maximum pulse energy of 60mJ is obtained.At 0.5Hz repetition rate,it can output 50mJ/pulse,at 1.54μm stably.Eexperiments indicate that the key of Er glass laser design is pumping symmetry and uniformity.
Erbium glass lasers can directly output 1.54μm eye-safe laser and can be used in eye-safe rangefinding applications.LD bar side-pumped Er+3,Yb+3 phosphate glass laser is reported.At free-running mode maximum pulse energy of 60mJ is obtained.At 0.5Hz repetition rate,it can output 50mJ/pulse,at 1.54μm stably.Eexperiments indicate that the key of Er glass laser design is pumping symmetry and uniformity.
2006, 30(3): 332-333,336.
Abstract:
Based on the Rayleigh diffraction integral and without use of the usual approximation,R>λ(λ is wavelength),an exact analytical expression for the axial intensity of nonparaxial Gaussian beams diffracted by a small circular aperture is derived.Then the conventional intensity definition and accurate intensity expression is comparatively studied.It is found that the difference between the two definitions depends on the f-parameter,truncation parameter δ and propagation distance z.
Based on the Rayleigh diffraction integral and without use of the usual approximation,R>λ(λ is wavelength),an exact analytical expression for the axial intensity of nonparaxial Gaussian beams diffracted by a small circular aperture is derived.Then the conventional intensity definition and accurate intensity expression is comparatively studied.It is found that the difference between the two definitions depends on the f-parameter,truncation parameter δ and propagation distance z.
2006, 30(3): 334-336.
Abstract:
The groove misalignment of the grating-pair compresor does affect its dispersion characteristics.The diffraction characteristics of grating-pair compressor is analyzed under the condition that the grating surfaces are parallel while the grating grooves are unparallel,and the optical path length of pulse passing through this system is derived.Then the second-order,third-order and fourth-order dispersions are calculated.The resulting relative dispersion errors compared with that the grating grooves are strictly parallel are shown.The vertical spectrum displacement in the output pulse is calculated and shown quantitatively as function of the angle between the grooves.The results show that gratings with low groove density are superior to that of high density ones,if the groove misalignment is unavoidable.
The groove misalignment of the grating-pair compresor does affect its dispersion characteristics.The diffraction characteristics of grating-pair compressor is analyzed under the condition that the grating surfaces are parallel while the grating grooves are unparallel,and the optical path length of pulse passing through this system is derived.Then the second-order,third-order and fourth-order dispersions are calculated.The resulting relative dispersion errors compared with that the grating grooves are strictly parallel are shown.The vertical spectrum displacement in the output pulse is calculated and shown quantitatively as function of the angle between the grooves.The results show that gratings with low groove density are superior to that of high density ones,if the groove misalignment is unavoidable.
