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RSS2005 Vol. 29, No. 5
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2005, 29(5): 449-451,469.
[Abstract]
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Abstract:
In the processing of cladding,the difference of density and character of compositions leads to component segregation,and the cracks in the laser cladding coating are mainly related to the component segregation.In order to decrease the defects,an electromagnetic stirring equipment for laser cladding has been designed and made.Electromagnetic stirring has been used in laser cladding processing.Laser cladding hard alloy with electromagnetic stirring is studied.The results show that electromagnetic stirring affect not only the macro-appearance,but also the micro-structure of the coating.It can refine the WC structure and make them homogeneous,and also refine the branch crystal in transition region of the coating.
In the processing of cladding,the difference of density and character of compositions leads to component segregation,and the cracks in the laser cladding coating are mainly related to the component segregation.In order to decrease the defects,an electromagnetic stirring equipment for laser cladding has been designed and made.Electromagnetic stirring has been used in laser cladding processing.Laser cladding hard alloy with electromagnetic stirring is studied.The results show that electromagnetic stirring affect not only the macro-appearance,but also the micro-structure of the coating.It can refine the WC structure and make them homogeneous,and also refine the branch crystal in transition region of the coating.
2005, 29(5): 452-454,458.
Abstract:
Based on three dimensional transient heat conduction equation and elastic stress-strain equation,the temperature rise,distortion and equivalent stress distribution of white bijou window irradiated by high power annular beam(λ=(1.315)μm) are simulated using a three dimensional finite element model(FEM).The temperature rise,distortion and equivalent stress distribution of fluoride glass window induced by high power hollow rectangular laser beam(λ=3.8μm) are also simulated.Laser intensity spatial gradient and attenuation in window are considered in computational model.
Based on three dimensional transient heat conduction equation and elastic stress-strain equation,the temperature rise,distortion and equivalent stress distribution of white bijou window irradiated by high power annular beam(λ=(1.315)μm) are simulated using a three dimensional finite element model(FEM).The temperature rise,distortion and equivalent stress distribution of fluoride glass window induced by high power hollow rectangular laser beam(λ=3.8μm) are also simulated.Laser intensity spatial gradient and attenuation in window are considered in computational model.
2005, 29(5): 455-458.
Abstract:
The rays'transmitting tracks in the dual-stage wedge type fiber optical isolator was described.Five dimensions coordinates were built at first,then the theories of crystal optics and solid geometry were used to get the right locations of the rays in between interfaces.At the same time the Faraday rotators were simplified in the analysis.The tracks of extraordinary ray were emphasized especially.With the method,the rays'lateral displacements,distance between two output rays and optical path difference can be computed precisely for a certain wedge type fiber optical isolator.
The rays'transmitting tracks in the dual-stage wedge type fiber optical isolator was described.Five dimensions coordinates were built at first,then the theories of crystal optics and solid geometry were used to get the right locations of the rays in between interfaces.At the same time the Faraday rotators were simplified in the analysis.The tracks of extraordinary ray were emphasized especially.With the method,the rays'lateral displacements,distance between two output rays and optical path difference can be computed precisely for a certain wedge type fiber optical isolator.
2005, 29(5): 459-461,487.
Abstract:
589nm radiation generated by the sum frequency generation(SFG) with double-axis crystals KTP and LBO from lasers of 1064nm and 1319nm is analyzed.Nonlinear susceptibility tensor for the sum frequency generation is derived and validated in the second harmonic generation.Phase-matching for SFG is calculated and the optimal phase-matching angle and effective sum frequency coefficient are given.
589nm radiation generated by the sum frequency generation(SFG) with double-axis crystals KTP and LBO from lasers of 1064nm and 1319nm is analyzed.Nonlinear susceptibility tensor for the sum frequency generation is derived and validated in the second harmonic generation.Phase-matching for SFG is calculated and the optimal phase-matching angle and effective sum frequency coefficient are given.
2005, 29(5): 462-465,483.
Abstract:
The two important characteristics of semiconductor optical amplifiers(SOA),gain and polarization,are introduced completely.In the section of gain characteristic,the phenomena of gain modulation and gain saturation are described.The methods to enhance the gain of SOA are presented.In the other section,the reasons resulting in polarization sensitivity of SOA are analyzed and the way to perform SOA with low gain polarization sensitivity is discussed.At last,the phenomenon of the phase polarization sensitivity in SOA paid much attention in recent years is reported.
The two important characteristics of semiconductor optical amplifiers(SOA),gain and polarization,are introduced completely.In the section of gain characteristic,the phenomena of gain modulation and gain saturation are described.The methods to enhance the gain of SOA are presented.In the other section,the reasons resulting in polarization sensitivity of SOA are analyzed and the way to perform SOA with low gain polarization sensitivity is discussed.At last,the phenomenon of the phase polarization sensitivity in SOA paid much attention in recent years is reported.
2005, 29(5): 466-469.
Abstract:
For the laser system performance,the threshold condition is of great significance.The threshold condition of C→A transition low gain,broadband-pulsed excimer laser is closely relative to the pump pulse.Based on the rate equations of four-level laser energy systems,the analytical methods of gain switching and Q-switch are used to study the threshold condition of the(C→A) transition low gain pulsed excimer laser.While the threshold conditions in the different gain duration are given.The analytical results show the threshold condition of the C→A transition low gain excimer laser is fundamentally different from the CW laser in short gain pulse,and depends on time integrated gain coefficient that has to exceed a critical value.
For the laser system performance,the threshold condition is of great significance.The threshold condition of C→A transition low gain,broadband-pulsed excimer laser is closely relative to the pump pulse.Based on the rate equations of four-level laser energy systems,the analytical methods of gain switching and Q-switch are used to study the threshold condition of the(C→A) transition low gain pulsed excimer laser.While the threshold conditions in the different gain duration are given.The analytical results show the threshold condition of the C→A transition low gain excimer laser is fundamentally different from the CW laser in short gain pulse,and depends on time integrated gain coefficient that has to exceed a critical value.
2005, 29(5): 470-472.
Abstract:
Based on the experimental research of the UV-light absorption spectra and the fluorescent spectra of methanol,the spectral characteristics and the physical mechanisms were investigated.The research outcomes indicate that methanol molecules can absorb the exciting light with a maximum wavelength of 260nm and they can emit fluorescence with a peak value of 340nm.And by means of the concentration change,fluorescent intensity had a regular change.Meanwhile the absorbing-emitting mechanism of methanol molecule was also discussed.The results of this research will give the theoretical support to measurement mini-quantity and reference to diagnose technique of methanol molecules.
Based on the experimental research of the UV-light absorption spectra and the fluorescent spectra of methanol,the spectral characteristics and the physical mechanisms were investigated.The research outcomes indicate that methanol molecules can absorb the exciting light with a maximum wavelength of 260nm and they can emit fluorescence with a peak value of 340nm.And by means of the concentration change,fluorescent intensity had a regular change.Meanwhile the absorbing-emitting mechanism of methanol molecule was also discussed.The results of this research will give the theoretical support to measurement mini-quantity and reference to diagnose technique of methanol molecules.
2005, 29(5): 473-475.
Abstract:
In the experiment of laser fusion, broadband lasers, which are weak interference, can effectively restrain high order nonlinear effects and smooth the radiation upon the target. According to the method of different frequency coupling,a model of the second harmonic generation (SHG) of the broadband lasers is set up. The calculation result shows that the bandwidth is compressed,which can be referenced by the third harmonic generation of the broadband lasers.
In the experiment of laser fusion, broadband lasers, which are weak interference, can effectively restrain high order nonlinear effects and smooth the radiation upon the target. According to the method of different frequency coupling,a model of the second harmonic generation (SHG) of the broadband lasers is set up. The calculation result shows that the bandwidth is compressed,which can be referenced by the third harmonic generation of the broadband lasers.
2005, 29(5): 476-477,490.
Abstract:
The development of the dense wavelength division multiplexing(DWDM) technology requires that the lasing wavelength of the light source have high accuracy and stability.The lasing wavelength stability of the fiber grating external cavity semiconductor lasers(FGESLs) is focused on.After taking into account the joint contribution of semiconductor laser,external cavity and fiber grating(FG) to the phase condition,the mode distribution of the FGESLs can be determined.As a result,the effect of the FG external cavity length on the lasing wavelength of the FGESL is investigated theoretically.Numerical simulations show that for a relative short external cavity,a slight change of the external cavity length will result in an obvious variation of the lasing wavelength;and for a long external cavity(>10cm),the change of the external cavity length gives almost no effect on the lasing wavelength.
The development of the dense wavelength division multiplexing(DWDM) technology requires that the lasing wavelength of the light source have high accuracy and stability.The lasing wavelength stability of the fiber grating external cavity semiconductor lasers(FGESLs) is focused on.After taking into account the joint contribution of semiconductor laser,external cavity and fiber grating(FG) to the phase condition,the mode distribution of the FGESLs can be determined.As a result,the effect of the FG external cavity length on the lasing wavelength of the FGESL is investigated theoretically.Numerical simulations show that for a relative short external cavity,a slight change of the external cavity length will result in an obvious variation of the lasing wavelength;and for a long external cavity(>10cm),the change of the external cavity length gives almost no effect on the lasing wavelength.
2005, 29(5): 478-480.
Abstract:
The Yb:ZnWO4 crystal is grown with Czochralski method.The polarized absorption spectra and polarized emission spectra are observed.The absorption cross section is 3.0×10-20cm2,fluorescence life time is 1.15ms and emission cross section is 2.0×10-20cm2.The Stark energy levels of Yb3+ in ZnWO4 crystal are analyzed.As a result of strong absorption at 972nm and broad fluorescence band from 914nm to 1055nm,Yb:ZnWO4 can be used as a new type of tunable laser crystal pumped by LD.
The Yb:ZnWO4 crystal is grown with Czochralski method.The polarized absorption spectra and polarized emission spectra are observed.The absorption cross section is 3.0×10-20cm2,fluorescence life time is 1.15ms and emission cross section is 2.0×10-20cm2.The Stark energy levels of Yb3+ in ZnWO4 crystal are analyzed.As a result of strong absorption at 972nm and broad fluorescence band from 914nm to 1055nm,Yb:ZnWO4 can be used as a new type of tunable laser crystal pumped by LD.
2005, 29(5): 481-483.
Abstract:
According to the theory of Fraunhofer diffraction,the MATLAB software is applied to proceed the emulation and the standard ellipsoid model of the different body factors is dissussed.Calculation results are compared with the experiment results.So that the ellipsoid model is comfirmed superior to the ball model in the particle measure,the particle size distribution of nonspherical particles can be obtained more accurately.Finally,the body factors of the particles are achined from the inversion to the diffraction pattern of ellipsoid model.
According to the theory of Fraunhofer diffraction,the MATLAB software is applied to proceed the emulation and the standard ellipsoid model of the different body factors is dissussed.Calculation results are compared with the experiment results.So that the ellipsoid model is comfirmed superior to the ball model in the particle measure,the particle size distribution of nonspherical particles can be obtained more accurately.Finally,the body factors of the particles are achined from the inversion to the diffraction pattern of ellipsoid model.
2005, 29(5): 484-487.
Abstract:
The reason,the condition and the degree of modal coupling and aliasing in wavefront reconstruction are pointed by simulating the measure and Zernike modal wavefront reconstruction course of 19-element Hartmann-Shack wavefront sensor.Considering the maximum distinguished modal and stability of calculation,the principle of selecting optimal value of Zernike reconstruction is found.The analysis of the accuracy of reconstruction shows that modal coupling is main error for 19-element Hartmann-Shack sensor's wavefront reconstruction.The condition and the accuracy of the wavefront measured with 19element Hartmann-Shack wavefront sensor is received.
The reason,the condition and the degree of modal coupling and aliasing in wavefront reconstruction are pointed by simulating the measure and Zernike modal wavefront reconstruction course of 19-element Hartmann-Shack wavefront sensor.Considering the maximum distinguished modal and stability of calculation,the principle of selecting optimal value of Zernike reconstruction is found.The analysis of the accuracy of reconstruction shows that modal coupling is main error for 19-element Hartmann-Shack sensor's wavefront reconstruction.The condition and the accuracy of the wavefront measured with 19element Hartmann-Shack wavefront sensor is received.
2005, 29(5): 488-490.
Abstract:
A fiber-coupled laser diode pumped Nd:YVO4 crystal,typeⅠ critical phase matching LBO crystal intra-cavity sum frequency mixing by 1064nm and 1342nm,orange-yellow laser at 593.5nm was reported.By using a two lenses-cavity resonator,with injection pump power of 1.6W,TEM00 mode orange-yellow,low noise laser at 593.5nm of 84mW was obtained at last,and the optical conversion efficiency was 5.3%,its M2 factor was less than 1.2.The experiments and analyses show that typeⅠ critical phase matching LBO crystal intra-cavity sum frequency mixing is an available technique for orange-yellow laser and it can be applied to other transition wavelengths in Nd:YVO4 or other laser with different laser gain crystals to obtain more all-solid-state lasers with different single wavelength.
A fiber-coupled laser diode pumped Nd:YVO4 crystal,typeⅠ critical phase matching LBO crystal intra-cavity sum frequency mixing by 1064nm and 1342nm,orange-yellow laser at 593.5nm was reported.By using a two lenses-cavity resonator,with injection pump power of 1.6W,TEM00 mode orange-yellow,low noise laser at 593.5nm of 84mW was obtained at last,and the optical conversion efficiency was 5.3%,its M2 factor was less than 1.2.The experiments and analyses show that typeⅠ critical phase matching LBO crystal intra-cavity sum frequency mixing is an available technique for orange-yellow laser and it can be applied to other transition wavelengths in Nd:YVO4 or other laser with different laser gain crystals to obtain more all-solid-state lasers with different single wavelength.
2005, 29(5): 491-493.
Abstract:
Several developed methods are described in detail.The principle,the status of development and the application situations of each method are displayed.The advantages and disadvantages are compared.Some ideas about its trend are given in the end.
Several developed methods are described in detail.The principle,the status of development and the application situations of each method are displayed.The advantages and disadvantages are compared.Some ideas about its trend are given in the end.
2005, 29(5): 494-496,500.
Abstract:
The geometric characteristics and optical properties of ship wake are studied.It is analyzed that the scattering idiosyncrasy of laser by small bubbles in wake which are difficult to diffuse and dissolve in short time.Based on the changes of the forward or backward laser scattering characteristics in time domain,frequency domain and space domain when torpedo comes in and goes out of the ship wake,a new torpedo-wake-homing scheme to shadow the target is proposed.Some laser-wake-homing ways are discussed and compared.It is confirmed that ascending laser-wake-homing means is the advanced non-acoustic wake homing method which not only does not injure the exterior structure of torpedo,but also can fix on the borderline of ship wake by laser scan.
The geometric characteristics and optical properties of ship wake are studied.It is analyzed that the scattering idiosyncrasy of laser by small bubbles in wake which are difficult to diffuse and dissolve in short time.Based on the changes of the forward or backward laser scattering characteristics in time domain,frequency domain and space domain when torpedo comes in and goes out of the ship wake,a new torpedo-wake-homing scheme to shadow the target is proposed.Some laser-wake-homing ways are discussed and compared.It is confirmed that ascending laser-wake-homing means is the advanced non-acoustic wake homing method which not only does not injure the exterior structure of torpedo,but also can fix on the borderline of ship wake by laser scan.
2005, 29(5): 497-500.
Abstract:
The performance of multiwavelength Yb-doped double-clad fiber lasers(DCFL) is analyzed based on a Fabry-Perot(F-P) flter,and the wavelength dependence of reflectivity of dichroic mirror in the filter has been taken into account.It is found that the reflectivity of DCF facets and dirchroic mirror can obviously influence the performance,and there is an optimal value of the reflectivity of DCF facets.Using this optimal value,satisfying output power and extinction-ratio can be achieved.And high pump power will improve the output power and extinction-ratio.By controlling the length of F-P filter,the multiwavelength number can be adjusted.
The performance of multiwavelength Yb-doped double-clad fiber lasers(DCFL) is analyzed based on a Fabry-Perot(F-P) flter,and the wavelength dependence of reflectivity of dichroic mirror in the filter has been taken into account.It is found that the reflectivity of DCF facets and dirchroic mirror can obviously influence the performance,and there is an optimal value of the reflectivity of DCF facets.Using this optimal value,satisfying output power and extinction-ratio can be achieved.And high pump power will improve the output power and extinction-ratio.By controlling the length of F-P filter,the multiwavelength number can be adjusted.
2005, 29(5): 501-503,506.
Abstract:
Through discussing physical mechanism of optical breakdown in air caused by high power laser and ionization,the formula of free electron density in laser focus regime was attained.In addition,the breakdown threshold formula was also obtained after considering the energy loss of electron elastic collision and recombination.The calculated results are consistent with the experimental data.
Through discussing physical mechanism of optical breakdown in air caused by high power laser and ionization,the formula of free electron density in laser focus regime was attained.In addition,the breakdown threshold formula was also obtained after considering the energy loss of electron elastic collision and recombination.The calculated results are consistent with the experimental data.
2005, 29(5): 504-506.
Abstract:
In order to improve the precision,a new system is presented to measure the optical activity based on the theory of polarization interference.The measurement result for a quartz crystal optical activity shows that the relative error is less than one percent and the precision and effeet is improved a lot than the traditional one.
In order to improve the precision,a new system is presented to measure the optical activity based on the theory of polarization interference.The measurement result for a quartz crystal optical activity shows that the relative error is less than one percent and the precision and effeet is improved a lot than the traditional one.
2005, 29(5): 507-510.
Abstract:
A theoretical model based on solid state energy band theory and energy conservation is developed which can describe temporal and spatial distribution of carriers in nonmetal materials during laser-induced damage.The relation between damage threshold,ablation depth and laser pulse duration,wavelength,energy fluence is studied with the model.The effects of the electronic properties of material on damage threshold and ablation depth are also discussed.The respective roles of multi-photon ionization,tunnel ionization,and avalanche ionization in laser induced damage are examined,and it is found that photo-ionization is always the most important role in the nonmetal materials during ultra-short laser induced damage.
A theoretical model based on solid state energy band theory and energy conservation is developed which can describe temporal and spatial distribution of carriers in nonmetal materials during laser-induced damage.The relation between damage threshold,ablation depth and laser pulse duration,wavelength,energy fluence is studied with the model.The effects of the electronic properties of material on damage threshold and ablation depth are also discussed.The respective roles of multi-photon ionization,tunnel ionization,and avalanche ionization in laser induced damage are examined,and it is found that photo-ionization is always the most important role in the nonmetal materials during ultra-short laser induced damage.
2005, 29(5): 511-513,521.
Abstract:
The laser and optics properties of several kinds of laser glass have been discussed.A new method is pointed out to increase the output energy of power-limited laser that is high gain glass and low nonlinear refractive index coefficient n2 glass used in an amplifier together.The simulated calculation by light propagation procedure shows that the configuration,using phosphate glass in the forepart of amplifier and fluorophosphate glass in the rear-end,can reduce the restriction on the output capability from B integral.The largest output energy has a increase of 10~20 percent.
The laser and optics properties of several kinds of laser glass have been discussed.A new method is pointed out to increase the output energy of power-limited laser that is high gain glass and low nonlinear refractive index coefficient n2 glass used in an amplifier together.The simulated calculation by light propagation procedure shows that the configuration,using phosphate glass in the forepart of amplifier and fluorophosphate glass in the rear-end,can reduce the restriction on the output capability from B integral.The largest output energy has a increase of 10~20 percent.
2005, 29(5): 514-515,560.
Abstract:
The CW LD end-pumped quasi-CW ultraviolet laser with Cr+4:YAG,KTP and LBO is described.When the power of the laser diode is 12W,the pulse repeated frequency is 10kHz,the power of the quasi-CW ultraviolet laser with similar single transverse mode is approximately 50mW.
The CW LD end-pumped quasi-CW ultraviolet laser with Cr+4:YAG,KTP and LBO is described.When the power of the laser diode is 12W,the pulse repeated frequency is 10kHz,the power of the quasi-CW ultraviolet laser with similar single transverse mode is approximately 50mW.
2005, 29(5): 516-518,532.
Abstract:
The recent progress of coherent combining of fiber lasers is briefly introduced.Then some typical coherent combination methods are analyzed.Finally,the best one is presented among many actual coherent combination techniques.
The recent progress of coherent combining of fiber lasers is briefly introduced.Then some typical coherent combination methods are analyzed.Finally,the best one is presented among many actual coherent combination techniques.
2005, 29(5): 519-521.
Abstract:
A model of the nonlinear function was established based on the general model of the self-mixing effects.The model was used to estimate the parameters in the model of the self-mixing effects in semiconductor lasers based on the curve fitting of nonlinear least squares method.The simulation shows that this algorithm has strong astringency,less iterative number and a high accuracy.This method is feasible for measuring the parameters in the model of the self-mixing effects.
A model of the nonlinear function was established based on the general model of the self-mixing effects.The model was used to estimate the parameters in the model of the self-mixing effects in semiconductor lasers based on the curve fitting of nonlinear least squares method.The simulation shows that this algorithm has strong astringency,less iterative number and a high accuracy.This method is feasible for measuring the parameters in the model of the self-mixing effects.
2005, 29(5): 522-524,527.
Abstract:
Theoretical model of single photon acquisition probability is established for free-space quantum key distribution.The expression of single photon acquisition probability is deduced from the fundamental-mode Gaussian beam.The parameters that influence the single photon acquisition probability are the transmitter's tracking-pointing error,the far-field divergence angle,the link distance between transmitter and receiver and the receiver's antenna aperture.The single photon acquisition probability is analyzed in numerical simulation for the link between a ground station and a satellite in a low earth orbit and it is normally on the order of 10-3~10-5.
Theoretical model of single photon acquisition probability is established for free-space quantum key distribution.The expression of single photon acquisition probability is deduced from the fundamental-mode Gaussian beam.The parameters that influence the single photon acquisition probability are the transmitter's tracking-pointing error,the far-field divergence angle,the link distance between transmitter and receiver and the receiver's antenna aperture.The single photon acquisition probability is analyzed in numerical simulation for the link between a ground station and a satellite in a low earth orbit and it is normally on the order of 10-3~10-5.
2005, 29(5): 525-527.
Abstract:
Both object wave and reference wave should be uniform in rainbow holograph,especially in mould pressing hologram master plate of prevent falsifier label.Binary optical element(BOE) can be used to obtain the uniform wave and BOE may be made by using of spatial light modulator in laboratory condition.
Both object wave and reference wave should be uniform in rainbow holograph,especially in mould pressing hologram master plate of prevent falsifier label.Binary optical element(BOE) can be used to obtain the uniform wave and BOE may be made by using of spatial light modulator in laboratory condition.
2005, 29(5): 528-532.
Abstract:
The potential damage of optical elements induced by the pencil beam in high power laser system is analyzed based on augmented matrix optics.The numerical results of positioning the ghost points in spatial filter of high power laser system are presented.It is shown that tilting one of lenses in the spatial filter can reduce(or eliminate) the potential damage of pencil beam.The result shows that using the misaligned optical lens system and tilting the lens can avoid the damage caused by pencil beams in high power laser system.
The potential damage of optical elements induced by the pencil beam in high power laser system is analyzed based on augmented matrix optics.The numerical results of positioning the ghost points in spatial filter of high power laser system are presented.It is shown that tilting one of lenses in the spatial filter can reduce(or eliminate) the potential damage of pencil beam.The result shows that using the misaligned optical lens system and tilting the lens can avoid the damage caused by pencil beams in high power laser system.
2005, 29(5): 533-534,545.
Abstract:
The side-coupling technology of micro-prism and double-cladding fiber was studied.A right-angle prism of(1mm×)1mm×1mm dimension was glued on the side surface of the double-cladding fiber whose dimension was 330μm×170μm.The tested laser was coupled into the inner cladding of double-cladding fiber through the micro-prism.The coupling efficiency was measured to be 86% or so.This method can be applied in the side-pumping of double-cladding fiber.
The side-coupling technology of micro-prism and double-cladding fiber was studied.A right-angle prism of(1mm×)1mm×1mm dimension was glued on the side surface of the double-cladding fiber whose dimension was 330μm×170μm.The tested laser was coupled into the inner cladding of double-cladding fiber through the micro-prism.The coupling efficiency was measured to be 86% or so.This method can be applied in the side-pumping of double-cladding fiber.
2005, 29(5): 535-537,554.
Abstract:
The relationship between the net gain of two kinds of glass with high dopant concentrations and pumping power,thread lengths is measured at room temperature.The results show that,under 100mW pumping power,the net gain of Er-doped glass thread with 0.19g/cm3 concentration is 1.96dB/cm,its threshold pumping power is 36mW and optimum length is 4.5cm.The net gain of Yb:Er-codoped glass thread with 1.1g/cm3 Yb-concentration and 0.12g/cm3 Er-concentration is 3.07dB/cm,its threshold pumping power is 28mW and optimum length is 2.5cm.That is,10dB total net gain can be obtained within 10cm length.The net gain of Yb:Er-codoped glass threads don't take on the trend of saturation when pumping power becomes stronger.It means that more sensitive ytterbium improves the net gain characteristics of the Er-doped fiber amplifiers.
The relationship between the net gain of two kinds of glass with high dopant concentrations and pumping power,thread lengths is measured at room temperature.The results show that,under 100mW pumping power,the net gain of Er-doped glass thread with 0.19g/cm3 concentration is 1.96dB/cm,its threshold pumping power is 36mW and optimum length is 4.5cm.The net gain of Yb:Er-codoped glass thread with 1.1g/cm3 Yb-concentration and 0.12g/cm3 Er-concentration is 3.07dB/cm,its threshold pumping power is 28mW and optimum length is 2.5cm.That is,10dB total net gain can be obtained within 10cm length.The net gain of Yb:Er-codoped glass threads don't take on the trend of saturation when pumping power becomes stronger.It means that more sensitive ytterbium improves the net gain characteristics of the Er-doped fiber amplifiers.
2005, 29(5): 538-540.
Abstract:
Based on the analysis of interference stripes of equal thickness generated by the parallel laser on optical wedge,a new scheme for laser orientation detection system is presented.The mathematic model of the scheme is introduced in detail,and its realization is provided.The system is composed of six optical wedges for orientation detection and the corresponding detection circuits.The orientation and wavelength of the incident laser are determined by measuring the space between interference stripes on optical wedges.The experimental data are given,which indicate that the system has some advantages such as high location precision and fast response.
Based on the analysis of interference stripes of equal thickness generated by the parallel laser on optical wedge,a new scheme for laser orientation detection system is presented.The mathematic model of the scheme is introduced in detail,and its realization is provided.The system is composed of six optical wedges for orientation detection and the corresponding detection circuits.The orientation and wavelength of the incident laser are determined by measuring the space between interference stripes on optical wedges.The experimental data are given,which indicate that the system has some advantages such as high location precision and fast response.
2005, 29(5): 541-542,557.
Abstract:
It's an important task to reduce the produce of the diacetyl during the beer's fermentation and prevent the reforming of diacetyl in ended beer.It is an effective method to the question of diacetyl to breed the diacetyl-less saccharomyces cereveseae by using the technology of laser induced mutation.In proper time and dosage,irradiating saccharomyces cereveseae with He-Ne laser as an induced mutation illuminant,can obtain a strain of diacetyl-less saccharomyces cereveseae.When the beer is made with this strain,the amount of diacetyl is 0.1253 mg/L,30% less than before.
It's an important task to reduce the produce of the diacetyl during the beer's fermentation and prevent the reforming of diacetyl in ended beer.It is an effective method to the question of diacetyl to breed the diacetyl-less saccharomyces cereveseae by using the technology of laser induced mutation.In proper time and dosage,irradiating saccharomyces cereveseae with He-Ne laser as an induced mutation illuminant,can obtain a strain of diacetyl-less saccharomyces cereveseae.When the beer is made with this strain,the amount of diacetyl is 0.1253 mg/L,30% less than before.
2005, 29(5): 543-545.
Abstract:
For the case of square end faces of the medium,focused Gaussian beam pumping,temperature field of laser medium end-pumped by laser diode(LD) has been studied by using finite element methods.The temperature and its distribution in the medium,such as Nd:YAG,are determined.At last the temperature field at the condition of improving the convective heat coefficient of medium's surface,reducing the coolant temperature or cooling the pumped face of rod is simulated.The results indicate thatit hardly fall the thermal effects by imoroving the convective heat coefficient of medium's surface and reducing the coolant temperature,but it can reduce the thermal effects virtually by cooling the pumped face of rod.
For the case of square end faces of the medium,focused Gaussian beam pumping,temperature field of laser medium end-pumped by laser diode(LD) has been studied by using finite element methods.The temperature and its distribution in the medium,such as Nd:YAG,are determined.At last the temperature field at the condition of improving the convective heat coefficient of medium's surface,reducing the coolant temperature or cooling the pumped face of rod is simulated.The results indicate thatit hardly fall the thermal effects by imoroving the convective heat coefficient of medium's surface and reducing the coolant temperature,but it can reduce the thermal effects virtually by cooling the pumped face of rod.
2005, 29(5): 546-548.
Abstract:
The simulation of the temperature field associated w ith laser surface quenching is discussed using finite element analysis software ANSYS.Based on the experiment data,a mathematic model is set up to describe the variation rules of the energy transfer coefficien.tOn the other hand,the model can be used to p redict the layer thickness of a material surface as a result of laser surface quenching accurately,which is a new researching idea for how to control the technical parameter and the layer thickness accurately.
The simulation of the temperature field associated w ith laser surface quenching is discussed using finite element analysis software ANSYS.Based on the experiment data,a mathematic model is set up to describe the variation rules of the energy transfer coefficien.tOn the other hand,the model can be used to p redict the layer thickness of a material surface as a result of laser surface quenching accurately,which is a new researching idea for how to control the technical parameter and the layer thickness accurately.
2005, 29(5): 549-551.
Abstract:
The principle and experimental technique of hiding optical instruments detection based on "Cat's eye" effect were described.The factors that influence the intensity of the reflection wave were analyzed both quantitatively and qualitatively with the method of ray tracing.Research results show that the incline and defocusing of reflection plane in optical instrument(such as telescope and camera) reduce the intensity of the "Cat's eye" reflection.For example,the ratio of the reflection energy of optical instrument and the pulse energy of scanning laser decreases from 3.3%(under the ideal reflection condition) to(0.03%)(for the defocusing) and 0.016%(for the incline) respectively,while the distance between the laser scanning setup and infrared camera is 1000m and the incidence angle of scanning laser is 0.3rad.
The principle and experimental technique of hiding optical instruments detection based on "Cat's eye" effect were described.The factors that influence the intensity of the reflection wave were analyzed both quantitatively and qualitatively with the method of ray tracing.Research results show that the incline and defocusing of reflection plane in optical instrument(such as telescope and camera) reduce the intensity of the "Cat's eye" reflection.For example,the ratio of the reflection energy of optical instrument and the pulse energy of scanning laser decreases from 3.3%(under the ideal reflection condition) to(0.03%)(for the defocusing) and 0.016%(for the incline) respectively,while the distance between the laser scanning setup and infrared camera is 1000m and the incidence angle of scanning laser is 0.3rad.
2005, 29(5): 552-554.
Abstract:
The influence of the three parameters,namely the beam size of Gaussian source,the source size and the detector size,on the three-dimensional optical transfer function(3-D OTF) of an incident light fluorescent confocal microscope is investigated,and the 3-D OTF of such a set-up is derived.The calculated results show that the beam size has an effect on choosing both the source size and the detector size by means of a gaussian beam with the smaller beam size,both the source size and the detector size can be increased,and better optical resolution and higher signal-noise-ratio can be reached,compared with those by means of a parallel beam.
The influence of the three parameters,namely the beam size of Gaussian source,the source size and the detector size,on the three-dimensional optical transfer function(3-D OTF) of an incident light fluorescent confocal microscope is investigated,and the 3-D OTF of such a set-up is derived.The calculated results show that the beam size has an effect on choosing both the source size and the detector size by means of a gaussian beam with the smaller beam size,both the source size and the detector size can be increased,and better optical resolution and higher signal-noise-ratio can be reached,compared with those by means of a parallel beam.
2005, 29(5): 555-557.
Abstract:
The development of the color seperating gratings(CSGs),used in the field of ICF,is introduced.The CSG's area is 80mm×80mm.The change of beam near field percentage modulation is tested when the CSG is put in the optics system on the XGⅡ laser facility.Experimental results show that no increase of beam near field percentage modulation is found when the CSG is put in the system under the low power density of 0.005GW/cm2.
The development of the color seperating gratings(CSGs),used in the field of ICF,is introduced.The CSG's area is 80mm×80mm.The change of beam near field percentage modulation is tested when the CSG is put in the optics system on the XGⅡ laser facility.Experimental results show that no increase of beam near field percentage modulation is found when the CSG is put in the system under the low power density of 0.005GW/cm2.
2005, 29(5): 558-560.
Abstract:
To improve a scanning microscope,a new optoelectronic scanning method and device is proposed.The device is based on a liquid crystal display(LCD),to form a phase-most spatial light modulator.The electronic addressed liquid crystal display forms different diffractive optical elements.The phase shift introduced by these elements makes it possible to control the position and focus of the scanning beam.With a LCD used in a scanning microscope,good result is achived,which indicates that the liquid crystal display can be used as the key element of the scanning system of the scanning microscope.
To improve a scanning microscope,a new optoelectronic scanning method and device is proposed.The device is based on a liquid crystal display(LCD),to form a phase-most spatial light modulator.The electronic addressed liquid crystal display forms different diffractive optical elements.The phase shift introduced by these elements makes it possible to control the position and focus of the scanning beam.With a LCD used in a scanning microscope,good result is achived,which indicates that the liquid crystal display can be used as the key element of the scanning system of the scanning microscope.
