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RSS2002 Vol. 26, No. 6
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2002, 26(6): 401-402,406.
[Abstract]
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Abstract:
On the basis of Siegman's criterion for good passive Q-switched,it is difficult to operate a diode-pumped,passive Q-switched Nd:YVO4 laser with Cr4+:YAG as the saturable absorber.The main difficulties arise from the fact that a Nd:YVO4 crystal has a high stimulated emission cross section.With a fiber coupled laser diode end pumping Nd:YVO4 laser,1.4W of CW output power has obtained under a pump level of 3.5W with optical conversion efficiency of 40%.The Q-switching operation of Nd:YVO4 laser with Cr4+:YAG as the saturable absorber was demonstrated.Q-switched pulses duration is 11.7ns with pulse repetition rate of 22kHz.
On the basis of Siegman's criterion for good passive Q-switched,it is difficult to operate a diode-pumped,passive Q-switched Nd:YVO4 laser with Cr4+:YAG as the saturable absorber.The main difficulties arise from the fact that a Nd:YVO4 crystal has a high stimulated emission cross section.With a fiber coupled laser diode end pumping Nd:YVO4 laser,1.4W of CW output power has obtained under a pump level of 3.5W with optical conversion efficiency of 40%.The Q-switching operation of Nd:YVO4 laser with Cr4+:YAG as the saturable absorber was demonstrated.Q-switched pulses duration is 11.7ns with pulse repetition rate of 22kHz.
2002, 26(6): 403-406.
Abstract:
The characteristic,mechanism and equipment machinery of laser induced chemical vapour deposition and laser ablation methods on nanopowders preparation are analyzed,the effects on laser nanopowders preparation are clarified,the present application and study situation of laser technique on the preparation of nanopowders are reviewed,the comments on the prospect of the technique are given.
The characteristic,mechanism and equipment machinery of laser induced chemical vapour deposition and laser ablation methods on nanopowders preparation are analyzed,the effects on laser nanopowders preparation are clarified,the present application and study situation of laser technique on the preparation of nanopowders are reviewed,the comments on the prospect of the technique are given.
2002, 26(6): 407-408.
Abstract:
The continuous 2μm laser of 90mW is got with Ti sapphire laser to pumping Tm,Ho:YLF microchip.Both the relation of output power with pump power and the conversion effciency relation of output power with pump power are obtained.At the same time,the influence of temperature on laser output power is put forward.
The continuous 2μm laser of 90mW is got with Ti sapphire laser to pumping Tm,Ho:YLF microchip.Both the relation of output power with pump power and the conversion effciency relation of output power with pump power are obtained.At the same time,the influence of temperature on laser output power is put forward.
2002, 26(6): 409-410,424.
Abstract:
Temperature characteristics of a mini-TEA CO2 laser are tested experimentally and analyzed theoretically.The results show that under the temperature range considered,the laser output pulse energy decreases almost linearly as the gas temperature increases.
Temperature characteristics of a mini-TEA CO2 laser are tested experimentally and analyzed theoretically.The results show that under the temperature range considered,the laser output pulse energy decreases almost linearly as the gas temperature increases.
2002, 26(6): 411-412,427.
Abstract:
Dependence of energy of single cycle pulses on the carrier phase has been studied for Gaussina,Lorentzian,hyperbolic secant and sinc pulses.For the above mentioned symmetric profiles,analytical functions termed F's,varying with the ratio of the envelop width Tp to cycle period T0,have been introduced and deduced to quantify the effect of the carrier phase on the pulse energy.Based on the derived analytical expressions of F's,detailed descriptions of the pulse energy variations have been presented.
Dependence of energy of single cycle pulses on the carrier phase has been studied for Gaussina,Lorentzian,hyperbolic secant and sinc pulses.For the above mentioned symmetric profiles,analytical functions termed F's,varying with the ratio of the envelop width Tp to cycle period T0,have been introduced and deduced to quantify the effect of the carrier phase on the pulse energy.Based on the derived analytical expressions of F's,detailed descriptions of the pulse energy variations have been presented.
2002, 26(6): 413-415,418.
Abstract:
The surface densification of the ceramic-matrix refractory materials could be readily achieved by laser surface modification technique with little damage to the substrate,and thus to enhance their erosion resistance owing to the significant advantages of this technique,such as high power density,rapid heating and cooling rate,reliable controllability and simplicity of the process.In present report,the status of this new technique is reviewed from the following aspects,namely the compositions of the refractory materials for laser surface treatment,the laser parameters,the macrostructure and microstructure of the laser treated zones and the erosion resistance.Finally the existing problems and prospect are put forward.
The surface densification of the ceramic-matrix refractory materials could be readily achieved by laser surface modification technique with little damage to the substrate,and thus to enhance their erosion resistance owing to the significant advantages of this technique,such as high power density,rapid heating and cooling rate,reliable controllability and simplicity of the process.In present report,the status of this new technique is reviewed from the following aspects,namely the compositions of the refractory materials for laser surface treatment,the laser parameters,the macrostructure and microstructure of the laser treated zones and the erosion resistance.Finally the existing problems and prospect are put forward.
2002, 26(6): 416-418.
Abstract:
Based on single mode rate equations of fiber ring semiconductor lasers and small signal method,the dependence of relaxation oscillation on the length of ring cavity is discussed.The results show that there is critical value of the length of ring cavity with certain parameters.Relaxation oscillation exists only when the length of ring cavity is below the value.Modulation response and bandwidth under direct-current modulation are also studied.
Based on single mode rate equations of fiber ring semiconductor lasers and small signal method,the dependence of relaxation oscillation on the length of ring cavity is discussed.The results show that there is critical value of the length of ring cavity with certain parameters.Relaxation oscillation exists only when the length of ring cavity is below the value.Modulation response and bandwidth under direct-current modulation are also studied.
2002, 26(6): 419-420,431.
Abstract:
Laser confocal scanning microscope is used successfully in the biological and medical research range,the three-dimension reconstruction of information is an important part of laser confocal scanning microscope system using a series of two-dimensional section image collected by LCSM. The paper researches the volume rendering for data sets from LCSM. According to the property of its data sets,we propose the maximum algorithm. The experimental results show that this method is the same with LCSM system and can produce vivid 3D image.
Laser confocal scanning microscope is used successfully in the biological and medical research range,the three-dimension reconstruction of information is an important part of laser confocal scanning microscope system using a series of two-dimensional section image collected by LCSM. The paper researches the volume rendering for data sets from LCSM. According to the property of its data sets,we propose the maximum algorithm. The experimental results show that this method is the same with LCSM system and can produce vivid 3D image.
2002, 26(6): 421-424.
Abstract:
The developing procedure of laser polishing technology is presented in this paper. The current situation of laser polishing and future perspective is also clarified. The emphasis is focused on the characteristics of laser polishing process and its interacting mechanism. The comparisons of laser polishing with other polishing techniques are performed roundly and deeply. The advantages of laser polishing are summed up and its problems are put forward.
The developing procedure of laser polishing technology is presented in this paper. The current situation of laser polishing and future perspective is also clarified. The emphasis is focused on the characteristics of laser polishing process and its interacting mechanism. The comparisons of laser polishing with other polishing techniques are performed roundly and deeply. The advantages of laser polishing are summed up and its problems are put forward.
2002, 26(6): 425-427.
Abstract:
LiYF4 crystal with high quality was successfully grown in CF4 atmosphere.The difference between the crystals grown in Ar and CF4 atmosphere is reported.X-ray indicates that the impurity formed in Ar growth atmosphere is mainly oxyfluoride,the impurity can be effectively eliminated in CF4 atmosphere.
LiYF4 crystal with high quality was successfully grown in CF4 atmosphere.The difference between the crystals grown in Ar and CF4 atmosphere is reported.X-ray indicates that the impurity formed in Ar growth atmosphere is mainly oxyfluoride,the impurity can be effectively eliminated in CF4 atmosphere.
2002, 26(6): 428-431.
Abstract:
Within the framework of the paraxial approximation the matrix decomposition and equivalent transformation of misaligned optical systems are studied in detail based on matrix method in optics.It has been shown that any 3×3 ABCDEF augmented matrix,which describes a misalighed optical system,can be represented by an ordered product of basic matrices of ^α,^β and ^δ types.
Within the framework of the paraxial approximation the matrix decomposition and equivalent transformation of misaligned optical systems are studied in detail based on matrix method in optics.It has been shown that any 3×3 ABCDEF augmented matrix,which describes a misalighed optical system,can be represented by an ordered product of basic matrices of ^α,^β and ^δ types.
2002, 26(6): 432-434,438.
Abstract:
According to principle of IR processing circuit and time constant of RC,the output signal of processing circuit is analyzed when laser irradiates IR system. At first,the output signal of processing circuit is disappear,then it becomes normal gradually. By theoretical analysis and experiment research,the disappearance of output signal in IR system is not only related with power and time of laser,but also related with the time constant of RC. The bigger of RC time constant,the longer the time which output signal of processing circuit is disappear and becomes normal. When laser irradiates IR system,the disturbance time of output signal is not only related with thermal effects generated by absorbed power of detector and filter,but also related with the time constant of RC in IR system. The experiment proves that the theoretical analysis is advisable.
According to principle of IR processing circuit and time constant of RC,the output signal of processing circuit is analyzed when laser irradiates IR system. At first,the output signal of processing circuit is disappear,then it becomes normal gradually. By theoretical analysis and experiment research,the disappearance of output signal in IR system is not only related with power and time of laser,but also related with the time constant of RC. The bigger of RC time constant,the longer the time which output signal of processing circuit is disappear and becomes normal. When laser irradiates IR system,the disturbance time of output signal is not only related with thermal effects generated by absorbed power of detector and filter,but also related with the time constant of RC in IR system. The experiment proves that the theoretical analysis is advisable.
2002, 26(6): 435-438.
Abstract:
The fluorescence spectra for whole blood,erythrocyte and hemoglobin from healthy and fresh experimental mice under the wavelength of 407nm (Δλ1/2≈18nm) excitation are measured by a grating spectrometer,and their emitting mechanism and spectral characteristic are investigated. The experimental results and theoretic analization about it are presented in this paper. It shows that the blood or erythrocyte emitting fluorescence quantum yield efficiency under 407nm-LED excitation may reach above 90%,the blood fluorescence mainly result from fluorophores of the erythrocyte,but fluorescence spectra of hemoglobin by 407nm-LED excitation are obviously different from that of erythrocyte,and the fluorescence quantum yield of cracked erythrocyte remarkably declines and its spectral profiles are being distorted with the consistency of the cracked erythrocyte increasing.
The fluorescence spectra for whole blood,erythrocyte and hemoglobin from healthy and fresh experimental mice under the wavelength of 407nm (Δλ1/2≈18nm) excitation are measured by a grating spectrometer,and their emitting mechanism and spectral characteristic are investigated. The experimental results and theoretic analization about it are presented in this paper. It shows that the blood or erythrocyte emitting fluorescence quantum yield efficiency under 407nm-LED excitation may reach above 90%,the blood fluorescence mainly result from fluorophores of the erythrocyte,but fluorescence spectra of hemoglobin by 407nm-LED excitation are obviously different from that of erythrocyte,and the fluorescence quantum yield of cracked erythrocyte remarkably declines and its spectral profiles are being distorted with the consistency of the cracked erythrocyte increasing.
2002, 26(6): 439-440,443.
Abstract:
This paper introduces a new method to stabilize output intensity of a laser with digital PID control. When the output intensity of a laser is changed,a feedback control signal processed by a digital PID regulator is used to control the current of a laser tube.The method obtains higher intensity stability.With the process of a single chip microcomputer,the control circuit is simplified. The laser is shown to be high precision for control and well stability for operation.
This paper introduces a new method to stabilize output intensity of a laser with digital PID control. When the output intensity of a laser is changed,a feedback control signal processed by a digital PID regulator is used to control the current of a laser tube.The method obtains higher intensity stability.With the process of a single chip microcomputer,the control circuit is simplified. The laser is shown to be high precision for control and well stability for operation.
2002, 26(6): 441-443.
Abstract:
The higher-order coherence function theory has been applied to study the fifth-order nonlinear effect on polarization beats of a cascade three-level system(FPBCTMS) in Markovian field.Based on analysis of the cases that pump beams are chaos fields,phase-diffusing field and real Gaussian field,compassed of beat signal in FPBCTMS are obtained.The effects of amplitude fluctuation and phase diffusing in the measurement of the energy-level difference are discussed.
The higher-order coherence function theory has been applied to study the fifth-order nonlinear effect on polarization beats of a cascade three-level system(FPBCTMS) in Markovian field.Based on analysis of the cases that pump beams are chaos fields,phase-diffusing field and real Gaussian field,compassed of beat signal in FPBCTMS are obtained.The effects of amplitude fluctuation and phase diffusing in the measurement of the energy-level difference are discussed.
2002, 26(6): 444-445.
Abstract:
This paper introduces a method of using 1079.5nm laser to irradiate or cauterize the pericoronitis of wisdom tooth.In 360 treatment cases,the cure rate is high up to 100%.Therefore the method are better than any others.
This paper introduces a method of using 1079.5nm laser to irradiate or cauterize the pericoronitis of wisdom tooth.In 360 treatment cases,the cure rate is high up to 100%.Therefore the method are better than any others.
2002, 26(6): 446-449.
Abstract:
The process of solid boronizing and laser surface treatment is applied to get boron eutectic layer to lower sample's crisp property and improve its wearing quality.To further discuss the technological feasibility,an abrasive wear experiment has been launched to prove it.Results show that this kind of compound processing technique can greatly prolong the life-span of the workpiece.
The process of solid boronizing and laser surface treatment is applied to get boron eutectic layer to lower sample's crisp property and improve its wearing quality.To further discuss the technological feasibility,an abrasive wear experiment has been launched to prove it.Results show that this kind of compound processing technique can greatly prolong the life-span of the workpiece.
2002, 26(6): 450-452,457.
Abstract:
The phase matching angle of Nd:GdCOB is calculated.Using Datachroom-5000 pulsed dye laser as pump source,we have realized the self-frequency-doubling laser from 1331.0nm to 665.5nm in Nd:GdCOB crystal. The experiment results show that the threshold energy for the crystal is 14.2mJ;when the pump energy is 25mJ,the output 665.5nm laser energy is 0.62mJ and the corresponding conversion efficiency is 2.5%.
The phase matching angle of Nd:GdCOB is calculated.Using Datachroom-5000 pulsed dye laser as pump source,we have realized the self-frequency-doubling laser from 1331.0nm to 665.5nm in Nd:GdCOB crystal. The experiment results show that the threshold energy for the crystal is 14.2mJ;when the pump energy is 25mJ,the output 665.5nm laser energy is 0.62mJ and the corresponding conversion efficiency is 2.5%.
2002, 26(6): 453-457.
Abstract:
The main factors affecting the measuring accuracy and stability of intensity modulated fiber optic sensor are put forward. In order to improve the performance of this kind sensor,compensation technique should be adopted to eliminate the influence induced by the external disturbance. More than ten kinds of compensation methods are described and compared in detail.
The main factors affecting the measuring accuracy and stability of intensity modulated fiber optic sensor are put forward. In order to improve the performance of this kind sensor,compensation technique should be adopted to eliminate the influence induced by the external disturbance. More than ten kinds of compensation methods are described and compared in detail.
2002, 26(6): 458-460.
Abstract:
LDV provides a non-intrusive useful tool to measure the local flow velocity within a relatively small measurement volume. Since it was developed in 1969,the dual-scatter or fringe type laser velocimeter have become the universally accepted standard. But it can not easily expanded to a three-component system. The nonorthogonal velocity is measured by LDV,from which the orthogonal three-dimensional components are computed through transformation equation. In this paper,the presented measurement techniques of nonorthogonal velocity with LDV gives useful help for application of LDV.
LDV provides a non-intrusive useful tool to measure the local flow velocity within a relatively small measurement volume. Since it was developed in 1969,the dual-scatter or fringe type laser velocimeter have become the universally accepted standard. But it can not easily expanded to a three-component system. The nonorthogonal velocity is measured by LDV,from which the orthogonal three-dimensional components are computed through transformation equation. In this paper,the presented measurement techniques of nonorthogonal velocity with LDV gives useful help for application of LDV.
2002, 26(6): 461-462,465.
Abstract:
The large aperture KDP electro-optical switch is a key unit for the new high-power laser multi-pass amplification system.In the article,the influence of orientation error on the switch performance is discussed,the manufacture,orientation,performance testing system are introduced.The testing results for a 240mm×240mm×14mm large aperture KDP switching crystal,developed by us for the first time,are reported.
The large aperture KDP electro-optical switch is a key unit for the new high-power laser multi-pass amplification system.In the article,the influence of orientation error on the switch performance is discussed,the manufacture,orientation,performance testing system are introduced.The testing results for a 240mm×240mm×14mm large aperture KDP switching crystal,developed by us for the first time,are reported.
2002, 26(6): 463-465.
Abstract:
The large aperture KDP electro-optical switch is a key unit for the new high-power laser multi-pass amplification system.In the article,the influence of orientation error on the switch performance is discussed,the manufacture,orientation,performance testing system are introduced.The testing results for a 240mm×240mm×14mm large aperture KDP switching crystal,developed by us for the first time,are reported.
The large aperture KDP electro-optical switch is a key unit for the new high-power laser multi-pass amplification system.In the article,the influence of orientation error on the switch performance is discussed,the manufacture,orientation,performance testing system are introduced.The testing results for a 240mm×240mm×14mm large aperture KDP switching crystal,developed by us for the first time,are reported.
Power gain of perturbation traveling inside amplifying nonlinear medium in terms of Breakup-integral
2002, 26(6): 466-467,470.
Abstract:
Numerical calculations have been used to solve wave equations coupling amplitude and phase of the light,applicable to the amplifying Kerr medium,studies have been made on the power gain of the perturbation varying with the break-up integral (i.e. B-integral).
Numerical calculations have been used to solve wave equations coupling amplitude and phase of the light,applicable to the amplifying Kerr medium,studies have been made on the power gain of the perturbation varying with the break-up integral (i.e. B-integral).
2002, 26(6): 468-470.
Abstract:
This paper describes a numerical study on the thawing of biological tissue induced by laser irradiation. The calculating results show that,although the laser beam heats the biological tissue in a volumetric manner,the thawing process of biological tissue induced by laser heating is similar to that induced by ordinary heating source. The absorption coefficient of biological tissue has a great influence on the thawing process. When the absorption coefficient increases,the thawing process induced by laser heating approaches that induced by ordinary heating source.
This paper describes a numerical study on the thawing of biological tissue induced by laser irradiation. The calculating results show that,although the laser beam heats the biological tissue in a volumetric manner,the thawing process of biological tissue induced by laser heating is similar to that induced by ordinary heating source. The absorption coefficient of biological tissue has a great influence on the thawing process. When the absorption coefficient increases,the thawing process induced by laser heating approaches that induced by ordinary heating source.
2002, 26(6): 471-473,477.
Abstract:
As the error probability is inherently high in optical storage,proper error correction coding methods must be adopted to ensure the validity of recorded data Reed-Solomon(RS) code is one of such codes that meet the requirements.In this paper,two different algorithms which implement RS code,Berlekamp-Massey(BM) algorithm and Peterson-Gorentstein-Zierler(PGZ) algorithm are analyzed and compared under specific application conditions with respect to different error occurrence case.And finally PGZ algorithm is implemented with VHDL and the simulation result shows it is practical to be implemented in FPGA.
As the error probability is inherently high in optical storage,proper error correction coding methods must be adopted to ensure the validity of recorded data Reed-Solomon(RS) code is one of such codes that meet the requirements.In this paper,two different algorithms which implement RS code,Berlekamp-Massey(BM) algorithm and Peterson-Gorentstein-Zierler(PGZ) algorithm are analyzed and compared under specific application conditions with respect to different error occurrence case.And finally PGZ algorithm is implemented with VHDL and the simulation result shows it is practical to be implemented in FPGA.
2002, 26(6): 474-477.
Abstract:
The paper deals with the results on processing parameters of laser transformation hardening and laser surface melting for HT300 camshaft of motorcycle by using(L934) orthogonal experiment.The results show that the two processing methods provide different characteristics respectively,which adopt to different practical technology requirement of camshaft surface.The analysis of structure with/without laser strength treatment and comparative tests of abrasive resistance measurement for sample HT300 prove that the surface hardness and wearability by laser strength treatment are better than chilling treatment.The experimental results provide a basis to improve the surface properties of components.
The paper deals with the results on processing parameters of laser transformation hardening and laser surface melting for HT300 camshaft of motorcycle by using(L934) orthogonal experiment.The results show that the two processing methods provide different characteristics respectively,which adopt to different practical technology requirement of camshaft surface.The analysis of structure with/without laser strength treatment and comparative tests of abrasive resistance measurement for sample HT300 prove that the surface hardness and wearability by laser strength treatment are better than chilling treatment.The experimental results provide a basis to improve the surface properties of components.
2002, 26(6): 478-480.
Abstract:
This paper introduces a new sheet metal forming technology using laser-induced shock waves,and analyzes its forming mechanisms,features,principle process factors and potential application fields. Finally some key techniques are pointed to be studied for industrial application of laser shock forming of metal sheet.
This paper introduces a new sheet metal forming technology using laser-induced shock waves,and analyzes its forming mechanisms,features,principle process factors and potential application fields. Finally some key techniques are pointed to be studied for industrial application of laser shock forming of metal sheet.
