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RSS2009 Vol. 33, No. 3
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2009, 33(3): 225-227.
[Abstract]
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Abstract:
In order to solve the serious thermal effect in high power end-pumped fiber lasers,the water-jet guided pump(WJGP) was proposed.In this pumping scheme,the pumping light is coupled into a high-speed water-jet similar to an opticalfiber.The light is guided by the jet and pumped into a following fiber.The thermal effects in the double-clad fiber laser underWJGP and traditional end-pump were analyzed and calculated respectively.With 800W pumping power,the maximum temperature of the pumped end face of fiber declined from 250℃ under traditional end-pump to 30℃ under WJGP,and the temperature of the fiber surface reduced greatly too.It is proved that the cooling effect of WJGP is significant,especially on the fiber's pumped end and the thermal damage on the pump end in a high power fiber laser can be effectively solved.
In order to solve the serious thermal effect in high power end-pumped fiber lasers,the water-jet guided pump(WJGP) was proposed.In this pumping scheme,the pumping light is coupled into a high-speed water-jet similar to an opticalfiber.The light is guided by the jet and pumped into a following fiber.The thermal effects in the double-clad fiber laser underWJGP and traditional end-pump were analyzed and calculated respectively.With 800W pumping power,the maximum temperature of the pumped end face of fiber declined from 250℃ under traditional end-pump to 30℃ under WJGP,and the temperature of the fiber surface reduced greatly too.It is proved that the cooling effect of WJGP is significant,especially on the fiber's pumped end and the thermal damage on the pump end in a high power fiber laser can be effectively solved.
2009, 33(3): 228-231.
Abstract:
In order to pump a solid disk laser effectively,edge-pumped scheme forYb:YAGthin disk solid-state laser wasadopted.More than 80% absorption efficiency and homogenous absorption distribution were obtained with an asymmetric composite crystal.The heat sink with its thermal conduction efficiency over 12W/(cm2·K) satisfied the system requirement forcooling well.In the experiment,maximum output power of over 123W was achieved with slope efficiency of 34.8%.The results show that it is prospective to adopt edge-pumped scheme for thin disk solid-state lasers.
In order to pump a solid disk laser effectively,edge-pumped scheme forYb:YAGthin disk solid-state laser wasadopted.More than 80% absorption efficiency and homogenous absorption distribution were obtained with an asymmetric composite crystal.The heat sink with its thermal conduction efficiency over 12W/(cm2·K) satisfied the system requirement forcooling well.In the experiment,maximum output power of over 123W was achieved with slope efficiency of 34.8%.The results show that it is prospective to adopt edge-pumped scheme for thin disk solid-state lasers.
2009, 33(3): 232-235.
Abstract:
The spectral phase shift of broadband pulse caused by transient random disturbance was investigated,based on the combination of the characteristics of linear chirped pulse and the spectral interferometry of two pulses.When the same component of both the pulse spectra meet on the frequency domain,the spectral interference is generated.Extracting spectral phase difference between both the linear chirped pulses from the spectral interferogram,it was simulated based on Fourier transform spectral interferometry(FTSI).The results show that reconstructed phase shift of chirped pulses is characteristic of spectral change,and this reconstruction algorithm is effective.This method is helpful to transient measurement of some physical quantity in ultrafast optics.
The spectral phase shift of broadband pulse caused by transient random disturbance was investigated,based on the combination of the characteristics of linear chirped pulse and the spectral interferometry of two pulses.When the same component of both the pulse spectra meet on the frequency domain,the spectral interference is generated.Extracting spectral phase difference between both the linear chirped pulses from the spectral interferogram,it was simulated based on Fourier transform spectral interferometry(FTSI).The results show that reconstructed phase shift of chirped pulses is characteristic of spectral change,and this reconstruction algorithm is effective.This method is helpful to transient measurement of some physical quantity in ultrafast optics.
2009, 33(3): 236-238,242.
Abstract:
In order to monitor and test the setting up angle of the parabolic mirror of the infrared tracking system of the missile seeker in the assembly process,a new approach was brought up,in which a CCD(charge coupled device) was used to receive the focusing spot of the parabolic mirror of the infrared tracking system of the focusing spot while rotating the parabolic mirror.The track of the center of gravity of the spot was fitted with the least square method,so the eccentric angle between the optical axis of the parabolic mirror and the structural central axis could be found.The method was analyzed in theory and proved in experiments.Different from the traditional transparent focusing system,the eccentric angle of the ring parabolic mirror was proportional to the radius R of the track circle of the center of gravity of the focusing spot with a coefficient of 1.13.The experimental results indicate that the system meets the need to monitor and test the setting up angle of the parabolic mirror.
In order to monitor and test the setting up angle of the parabolic mirror of the infrared tracking system of the missile seeker in the assembly process,a new approach was brought up,in which a CCD(charge coupled device) was used to receive the focusing spot of the parabolic mirror of the infrared tracking system of the focusing spot while rotating the parabolic mirror.The track of the center of gravity of the spot was fitted with the least square method,so the eccentric angle between the optical axis of the parabolic mirror and the structural central axis could be found.The method was analyzed in theory and proved in experiments.Different from the traditional transparent focusing system,the eccentric angle of the ring parabolic mirror was proportional to the radius R of the track circle of the center of gravity of the focusing spot with a coefficient of 1.13.The experimental results indicate that the system meets the need to monitor and test the setting up angle of the parabolic mirror.
2009, 33(3): 239-242.
Abstract:
Mach-Zehnder heterodyne interferometric polarimeter can precisely measure the polarization state of light in real time.In order to improve the measurement precision and reduce the nonlinear erzor,which arises from the elliptical polarization of the laser,polarization leakage of the polarized beam sputter(PBS) and misalignment of the PBS were analyzed.The erzor formula was deduced.The simulation results showed that different amplitude ratio and phase difference of the measured beam had different nonlinear error output.The erzor was quite similar to the nonlinear erzor calculated in the Michelson heterodyne interferometer.
Mach-Zehnder heterodyne interferometric polarimeter can precisely measure the polarization state of light in real time.In order to improve the measurement precision and reduce the nonlinear erzor,which arises from the elliptical polarization of the laser,polarization leakage of the polarized beam sputter(PBS) and misalignment of the PBS were analyzed.The erzor formula was deduced.The simulation results showed that different amplitude ratio and phase difference of the measured beam had different nonlinear error output.The erzor was quite similar to the nonlinear erzor calculated in the Michelson heterodyne interferometer.
2009, 33(3): 243-245,255.
Abstract:
In order to study the effect of the fog particles scattering on laser guidance and improve the guidance precision of guided weapons,based on Mie theory,considering the particle size distribution function,the scattering model of the group particles was obtained.With the help of the model,the relationship between the target position deviation angle and the scattering intensity was obtained and the effect of scattered light on the signal was analyzed from the view of scattering.The calculation showed that the echo signal was influenced obviously by the backscattered light from the atmospheric particles at a certain scale distribution.The results are valuable for the study on the effect of back scattering of atmospheric particles on the laser-guided precision.
In order to study the effect of the fog particles scattering on laser guidance and improve the guidance precision of guided weapons,based on Mie theory,considering the particle size distribution function,the scattering model of the group particles was obtained.With the help of the model,the relationship between the target position deviation angle and the scattering intensity was obtained and the effect of scattered light on the signal was analyzed from the view of scattering.The calculation showed that the echo signal was influenced obviously by the backscattered light from the atmospheric particles at a certain scale distribution.The results are valuable for the study on the effect of back scattering of atmospheric particles on the laser-guided precision.
2009, 33(3): 246-248,272.
Abstract:
In order to study the influence of additive on laser transmission welding thermoplastic material,the experimental scheme of laser transmission welding thermoplastic material was designed.Laser transmission welding transparent polystyrene and polyvinyl chloride was successful with this method.The welding process was analysized with orthogonal method.The shear strength was tested on the workpiece.The influence of two kinds of additive;black lacquer and clearweld on welding strengnh and appearance quality was discussed.Finally,the phenomenon of black and brown welding line,welding line heave,jointing rapture was analyzed.Experiment results showed that clearweld additive was better than black lacquer additive.
In order to study the influence of additive on laser transmission welding thermoplastic material,the experimental scheme of laser transmission welding thermoplastic material was designed.Laser transmission welding transparent polystyrene and polyvinyl chloride was successful with this method.The welding process was analysized with orthogonal method.The shear strength was tested on the workpiece.The influence of two kinds of additive;black lacquer and clearweld on welding strengnh and appearance quality was discussed.Finally,the phenomenon of black and brown welding line,welding line heave,jointing rapture was analyzed.Experiment results showed that clearweld additive was better than black lacquer additive.
2009, 33(3): 249-251.
Abstract:
By redesigning the film with substituting SiO2 instead of MgF2 as the outer layer film,the frequency doubling anti-reflection coating on the KTP crystal is improved.After the KTP crystal with 1064nm and 532nm antireflection coating is applied in high power Q-switched Nd:YAG laser,any surface damage have not been observed even at intensity as high as 450MW/cm2 at a pulse repetition rate of 1kHz and 25ns of pulse duration.The experimental results show that both the surface quality and the optical property of the film have been improved.
By redesigning the film with substituting SiO2 instead of MgF2 as the outer layer film,the frequency doubling anti-reflection coating on the KTP crystal is improved.After the KTP crystal with 1064nm and 532nm antireflection coating is applied in high power Q-switched Nd:YAG laser,any surface damage have not been observed even at intensity as high as 450MW/cm2 at a pulse repetition rate of 1kHz and 25ns of pulse duration.The experimental results show that both the surface quality and the optical property of the film have been improved.
2009, 33(3): 252-255.
Abstract:
In order to obtain better Fe-C alloy film,a knife-pen was used to eliminate the coating and cladding of fibers effectively instead of conventional HF acid method.The fiber core was metallized by means of ion sputtering Au or Fe-C,vacuum evaporating Fe-C,electroless plating Cu respectively.Then Fe-C film in different thickness was electroplated on the Cu film and Au film.After testing the sensing properties of the different thickness of Fe-C film a new way was proposed to monitor corrosion quantitatively,a conclusion was drawn that the ion sputtering Au was the best way to metallize the fiber core,which should be helpful for the future research of the optical fiber corrosion sensor with Fe-C alloy film.
In order to obtain better Fe-C alloy film,a knife-pen was used to eliminate the coating and cladding of fibers effectively instead of conventional HF acid method.The fiber core was metallized by means of ion sputtering Au or Fe-C,vacuum evaporating Fe-C,electroless plating Cu respectively.Then Fe-C film in different thickness was electroplated on the Cu film and Au film.After testing the sensing properties of the different thickness of Fe-C film a new way was proposed to monitor corrosion quantitatively,a conclusion was drawn that the ion sputtering Au was the best way to metallize the fiber core,which should be helpful for the future research of the optical fiber corrosion sensor with Fe-C alloy film.
2009, 33(3): 256-258.
Abstract:
In order to study the photonic band gap and dispersion property of a dual-core photonic crystal fiber(PCF),the photonic band gap was calculated with the plane-wave expansion method.The calculation results show that when the relative aperture(d/Λ)is larger than 0.2,the normalized propagation constant(β/Λ)increases,so the prohibited band and the range of wavelength propagating in the air-core increase.Secondly,the dispersion property of a dual-core was analyzed with a full vector model.The results show that the dispersion property can be adjusted with different structure parameters of fibers.Results show about 480nm of super flat dispersion area near 1.55μm can be obtained with Λ=2μm,d/Λ=0.4; with the relative aperture and aperture distance increasing,zero dispersion point will move to shorter-wave.The results of this study provide an effective way to produce efficient transmission optical fibers and high-performance polarization fibers.
In order to study the photonic band gap and dispersion property of a dual-core photonic crystal fiber(PCF),the photonic band gap was calculated with the plane-wave expansion method.The calculation results show that when the relative aperture(d/Λ)is larger than 0.2,the normalized propagation constant(β/Λ)increases,so the prohibited band and the range of wavelength propagating in the air-core increase.Secondly,the dispersion property of a dual-core was analyzed with a full vector model.The results show that the dispersion property can be adjusted with different structure parameters of fibers.Results show about 480nm of super flat dispersion area near 1.55μm can be obtained with Λ=2μm,d/Λ=0.4; with the relative aperture and aperture distance increasing,zero dispersion point will move to shorter-wave.The results of this study provide an effective way to produce efficient transmission optical fibers and high-performance polarization fibers.
2009, 33(3): 259-261,265.
Abstract:
In order to improve coupling character of dual-core photonic crystal fiber coupler,optimum models of dual-core photonic crystal fiber coupler were obtained by changing the structure and the refractive index of the air hole between both cores.Based on beam propagation method,the effect of the dimension of air hole between the cores and the refractive index of the injected material on the coupling property of the dual-core photonic crystal fiber coupler was analyzed by numerical calculation.Results of numerical calculation showed that the loss coefficient of the fiber maintained constant because the whole stmcture of the fiber kept unchanged.No matter the air hole between both cores decreased or the refractive index increased,the coupling length became shorter,the difference between coupling length for both polarized light became smaller and the loss became lower.Furthermore,it was easy to modulate the coupling character for the refractive index in the air hole between both cores was easy to adjusted.This method provides theoretical support for the optimum design of the models of dual-core photonic crystal fiber coupler.
In order to improve coupling character of dual-core photonic crystal fiber coupler,optimum models of dual-core photonic crystal fiber coupler were obtained by changing the structure and the refractive index of the air hole between both cores.Based on beam propagation method,the effect of the dimension of air hole between the cores and the refractive index of the injected material on the coupling property of the dual-core photonic crystal fiber coupler was analyzed by numerical calculation.Results of numerical calculation showed that the loss coefficient of the fiber maintained constant because the whole stmcture of the fiber kept unchanged.No matter the air hole between both cores decreased or the refractive index increased,the coupling length became shorter,the difference between coupling length for both polarized light became smaller and the loss became lower.Furthermore,it was easy to modulate the coupling character for the refractive index in the air hole between both cores was easy to adjusted.This method provides theoretical support for the optimum design of the models of dual-core photonic crystal fiber coupler.
2009, 33(3): 262-265.
Abstract:
In order to improve tracking precision,and solve the control problem of uncertainty of beacon vibration,creep resistance and nonlinearity long lagging of fast steering mirror(FSM),the fine tracking servo system was designed based on the proportion-integral-differential(PID) like neural network algorithm in free spatial optic(FSO) communication.With three layers of back propagation(BP) neural networks,the weights of neural network and the parameters could be adjusted to reduce beacon vibration by means of the function of self-learning and adaptability in real time,finally the system was optimally controlled with the mirror drived by piezoelectric ceramic(PZT) actuator on line.Experimental results demonstrate that the system effectively restrains 40Hz and less than 40Hz facular trembles,and can satisfy the tracking bandwidth in free space optic communication.Furthermore,the robust performance and real time are improved in the fine tracking servo system.
In order to improve tracking precision,and solve the control problem of uncertainty of beacon vibration,creep resistance and nonlinearity long lagging of fast steering mirror(FSM),the fine tracking servo system was designed based on the proportion-integral-differential(PID) like neural network algorithm in free spatial optic(FSO) communication.With three layers of back propagation(BP) neural networks,the weights of neural network and the parameters could be adjusted to reduce beacon vibration by means of the function of self-learning and adaptability in real time,finally the system was optimally controlled with the mirror drived by piezoelectric ceramic(PZT) actuator on line.Experimental results demonstrate that the system effectively restrains 40Hz and less than 40Hz facular trembles,and can satisfy the tracking bandwidth in free space optic communication.Furthermore,the robust performance and real time are improved in the fine tracking servo system.
2009, 33(3): 266-268,286.
Abstract:
The property of dual defect modes,induced by one-dimension photonic crystals containing absorbing defect layer with zero average refractivity,was studied based on the eigen matrix.The results show the transmissivity of dual defect modes varied with the extinction coefficient,and the transmissivity at high or low frequency defect mode became maximum as the extinction coefficient reached a certain value.However,the transmissivity at high or low defect frequency mode could not reached maximum value at the same time.In addition,the position of absorbing material might affect the response curve of dual defect modes.The conclusion will play an important impact on the application of photonic crystals.
The property of dual defect modes,induced by one-dimension photonic crystals containing absorbing defect layer with zero average refractivity,was studied based on the eigen matrix.The results show the transmissivity of dual defect modes varied with the extinction coefficient,and the transmissivity at high or low frequency defect mode became maximum as the extinction coefficient reached a certain value.However,the transmissivity at high or low defect frequency mode could not reached maximum value at the same time.In addition,the position of absorbing material might affect the response curve of dual defect modes.The conclusion will play an important impact on the application of photonic crystals.
2009, 33(3): 269-272.
Abstract:
Because of the interaction between the laser and water,the laser-induced signal is much different at different focusing position.In order to study the effect of focusing position on the acoustic wave,a setup was built to test the laser-induced acoustic wave.Experimental results show that the pulse width of the acoustic wave is related to that of laser pulse,and isindependent of laser focusing position.The focusing position only affects the time-domain profile and intensity of the acoustic wave.Furthermore,laser-induced plasma in air should be avoided.The results are helpful for further study on laser-induced acoustic wave.
Because of the interaction between the laser and water,the laser-induced signal is much different at different focusing position.In order to study the effect of focusing position on the acoustic wave,a setup was built to test the laser-induced acoustic wave.Experimental results show that the pulse width of the acoustic wave is related to that of laser pulse,and isindependent of laser focusing position.The focusing position only affects the time-domain profile and intensity of the acoustic wave.Furthermore,laser-induced plasma in air should be avoided.The results are helpful for further study on laser-induced acoustic wave.
2009, 33(3): 273-275,290.
Abstract:
In order to obtain 589nm yellow laser with high beam quality and high stability,double acousto-optic Q-switches and T-shaped composite cavity were adopted.Diode-side-pumped Nd:YAG and KTP intracavity sum-frequency converter with Ⅱ-type critical phase-matching were used.On the basis of theoretical analysis and experimental verification,the maximum power of 589nm laser reached 3.8W with pulse width of 135ns when the total pumping current was 36A and the repetition frequency was 10kHz.The result showed that high beam quality and high stable 589nm laser could be obtained by means of T-shaped composite cavity.This result is quite helpful for the realization of yellow laser application in the medical field.
In order to obtain 589nm yellow laser with high beam quality and high stability,double acousto-optic Q-switches and T-shaped composite cavity were adopted.Diode-side-pumped Nd:YAG and KTP intracavity sum-frequency converter with Ⅱ-type critical phase-matching were used.On the basis of theoretical analysis and experimental verification,the maximum power of 589nm laser reached 3.8W with pulse width of 135ns when the total pumping current was 36A and the repetition frequency was 10kHz.The result showed that high beam quality and high stable 589nm laser could be obtained by means of T-shaped composite cavity.This result is quite helpful for the realization of yellow laser application in the medical field.
2009, 33(3): 276-278,282.
Abstract:
In order to study the problem of aperture synthesizing in digital holography,the method of theoretical analysis and experimental verification was adopted.The fundamental principle of recording and numerical reconstruction of the synthetic aperture digital holography was introduced.It was proved that the most important factor was synthesizing all the sub-holograms precisely to get the high resolution.A new method based on gray correlation algorithm for solving the problem on how to synthesize sub-holograms precisely was proposed.The principle of the algorithm was introduced and the precision was analyzed.The experiment results show the feasibility of the algorithm.
In order to study the problem of aperture synthesizing in digital holography,the method of theoretical analysis and experimental verification was adopted.The fundamental principle of recording and numerical reconstruction of the synthetic aperture digital holography was introduced.It was proved that the most important factor was synthesizing all the sub-holograms precisely to get the high resolution.A new method based on gray correlation algorithm for solving the problem on how to synthesize sub-holograms precisely was proposed.The principle of the algorithm was introduced and the precision was analyzed.The experiment results show the feasibility of the algorithm.
2009, 33(3): 279-282.
Abstract:
In order that numerical simulation of the bidirectional pumped,erbium and ytterbium co-doped phosphate glass waveguide laser fabricated by femtosecond laser pulses was performed,based on the transition rate equations and propagation equations of the erbium and ytterbium co-doped system,the optimal parameters such as the size of the waveguide,output coupler reflectivity,the ratio of Er3+/Yb3+ were obtained.The results indicated that with the parameters of 10mm long waveguide,0.6 of the mirror reflectivity and 3.6 of the ratio of Er3+/Yb3+,the laser at 1535nm output up to 57mW with the pump power of 400mW at 975nm.The theoretical analysis agreed well with the experimental results reported so far.The simulation results provide a rigid theoretical Ease for the fabrication of active glass waveguide and the design of femtosecond laser.
In order that numerical simulation of the bidirectional pumped,erbium and ytterbium co-doped phosphate glass waveguide laser fabricated by femtosecond laser pulses was performed,based on the transition rate equations and propagation equations of the erbium and ytterbium co-doped system,the optimal parameters such as the size of the waveguide,output coupler reflectivity,the ratio of Er3+/Yb3+ were obtained.The results indicated that with the parameters of 10mm long waveguide,0.6 of the mirror reflectivity and 3.6 of the ratio of Er3+/Yb3+,the laser at 1535nm output up to 57mW with the pump power of 400mW at 975nm.The theoretical analysis agreed well with the experimental results reported so far.The simulation results provide a rigid theoretical Ease for the fabrication of active glass waveguide and the design of femtosecond laser.
2009, 33(3): 283-286.
Abstract:
In order to improve the efficiency of short pulse laser drilling,a double-pulse technique is put forward.The double-pulse herein represents two neighboring nanosecond pulses with several tens of nanoseconds interpulse separation,acquired by temporal pulse shaping.In the experiments,laser beams from a Q-switched Nd: YLF laser was focused on steel workpieces 0.4mm~1.0mm thick.The influence of energy density,repetition rate and the ambient gas pressure on ablation rate was studied. Che experimental results show a significant enhancement of ablation rates using double-pulse instead of conventional single-pulse under the same condition of energy density and pulse repetition frequency.The ablation mechanism of the double-pulse drilling,intauding material preheating,melt flow accelerating and quasi-vacuum environment,was discussed respectively.These results are important for practical efficient laser drilling.
In order to improve the efficiency of short pulse laser drilling,a double-pulse technique is put forward.The double-pulse herein represents two neighboring nanosecond pulses with several tens of nanoseconds interpulse separation,acquired by temporal pulse shaping.In the experiments,laser beams from a Q-switched Nd: YLF laser was focused on steel workpieces 0.4mm~1.0mm thick.The influence of energy density,repetition rate and the ambient gas pressure on ablation rate was studied. Che experimental results show a significant enhancement of ablation rates using double-pulse instead of conventional single-pulse under the same condition of energy density and pulse repetition frequency.The ablation mechanism of the double-pulse drilling,intauding material preheating,melt flow accelerating and quasi-vacuum environment,was discussed respectively.These results are important for practical efficient laser drilling.
2009, 33(3): 287-290.
Abstract:
In order to study nonvolatile holographic storage of near-stoichiometric Ce: Fe: LiNbO3 crystal,the spectrum of near-stoichiometric Ce: Fe: LiNbO3 crystal was tested.The results indicated that the infrared transmission spectra of the near-stoichiometric Ce: Fe:LiNbO3 crystal was narrower than that of congruent Ce:Fe:LiNbO3 crystal.the peak was located at 3466cm-1,and its ultraviolet spectrum shifted forward to violet.With single-photon and two-photon storage methods,nonvolatile holographic storage of near-stoichiometric Ce:Fe:LiNbO3 crystal was realized in theory and experiment.The results showed that in the single-photon storage experiments,the diffraction efficiency with the presence of mercury lamp became higher than that without mercury lamp.The performance in two-photon storage scheme was better than that in single-photon storage scheme.
In order to study nonvolatile holographic storage of near-stoichiometric Ce: Fe: LiNbO3 crystal,the spectrum of near-stoichiometric Ce: Fe: LiNbO3 crystal was tested.The results indicated that the infrared transmission spectra of the near-stoichiometric Ce: Fe:LiNbO3 crystal was narrower than that of congruent Ce:Fe:LiNbO3 crystal.the peak was located at 3466cm-1,and its ultraviolet spectrum shifted forward to violet.With single-photon and two-photon storage methods,nonvolatile holographic storage of near-stoichiometric Ce:Fe:LiNbO3 crystal was realized in theory and experiment.The results showed that in the single-photon storage experiments,the diffraction efficiency with the presence of mercury lamp became higher than that without mercury lamp.The performance in two-photon storage scheme was better than that in single-photon storage scheme.
2009, 33(3): 291-293,296.
Abstract:
In order to investigate more than one hundred Watt green laser,two serial rods pumped by laser diodes and two Q-switched V-shaped resonators were used.Based on the transmission matrixes,when single and double rods were placed in the cavity respectively,the stable condition of cavity,the light distribution in the folded arm,along with the sagittal and tangential spot size on the nonlinear crystal influenced by the thermal lens effect were analyzed and compared.A high gray tracking resistivity (HGTR)-KTP crystal with type Ⅱ critical phase-matching was adopted as intracavity frequency doubler.When the pump power of two diode lasers was 1200W and the repetition rate was 27.2kHz,164W green laser with the pulse width of 130ns was obtained.The optical-optical conversion efficiency was 13.7%.The beam quality factor was M32=10.46,M32=10.59.The result shows that one hundred Watt green laser could be obtained in the two-rod and two Q-switched V-shaped resonator configuration.
In order to investigate more than one hundred Watt green laser,two serial rods pumped by laser diodes and two Q-switched V-shaped resonators were used.Based on the transmission matrixes,when single and double rods were placed in the cavity respectively,the stable condition of cavity,the light distribution in the folded arm,along with the sagittal and tangential spot size on the nonlinear crystal influenced by the thermal lens effect were analyzed and compared.A high gray tracking resistivity (HGTR)-KTP crystal with type Ⅱ critical phase-matching was adopted as intracavity frequency doubler.When the pump power of two diode lasers was 1200W and the repetition rate was 27.2kHz,164W green laser with the pulse width of 130ns was obtained.The optical-optical conversion efficiency was 13.7%.The beam quality factor was M32=10.46,M32=10.59.The result shows that one hundred Watt green laser could be obtained in the two-rod and two Q-switched V-shaped resonator configuration.
2009, 33(3): 294-296.
Abstract:
In order to obtain a broadband tunable coherent sottrce,based on Mg0-doped periodically-poled lithium niobate,an optical parametric oscillator(OPO)was pumped by a 1064nm acousto-optically q-witched Nd: YAG laser,which can be conveniently tuned by means of changing its temperature.When the crystal temperature was adjusted from 40℃ to 200℃,the tunable mid-infrared output wavelength shifted from 1.565μN,m to 1.670μm.When the average pump power was 1.61w with about 70ns pulse duration operating at a repetition rate of 10kHz,the maximum signal output power of the OPO was about 211mW at 1631nm.It was shown from the results that temperature tunable optical parametric oscillator was a candidate of broadband tunable coherent sources.
In order to obtain a broadband tunable coherent sottrce,based on Mg0-doped periodically-poled lithium niobate,an optical parametric oscillator(OPO)was pumped by a 1064nm acousto-optically q-witched Nd: YAG laser,which can be conveniently tuned by means of changing its temperature.When the crystal temperature was adjusted from 40℃ to 200℃,the tunable mid-infrared output wavelength shifted from 1.565μN,m to 1.670μm.When the average pump power was 1.61w with about 70ns pulse duration operating at a repetition rate of 10kHz,the maximum signal output power of the OPO was about 211mW at 1631nm.It was shown from the results that temperature tunable optical parametric oscillator was a candidate of broadband tunable coherent sources.
2009, 33(3): 297-299,313.
Abstract:
In order to study the influence of UV pulse laser pre-treatment on surface image of fused silica and validate its upgrade effect on anti UV laser damage ability of fused silica,using 355nm YAG laser raster to scan fused silica optics by means of power increase 6y degrees periodically,the change of surface image was studied and its anti-laser damage threshold at 355nm was measured.Test results showed that surface impurity was cleaned out and it was found that the zero probability damage-threshold increased 24% and 50% probability damage-threshold increased 19%.The result proves UV laser pre-treatment is an effective method to increase anti UV laser damage ability and break through the bottleneck of high power laser output at 355nm,laser pre-treatment have practical value in engineering.
In order to study the influence of UV pulse laser pre-treatment on surface image of fused silica and validate its upgrade effect on anti UV laser damage ability of fused silica,using 355nm YAG laser raster to scan fused silica optics by means of power increase 6y degrees periodically,the change of surface image was studied and its anti-laser damage threshold at 355nm was measured.Test results showed that surface impurity was cleaned out and it was found that the zero probability damage-threshold increased 24% and 50% probability damage-threshold increased 19%.The result proves UV laser pre-treatment is an effective method to increase anti UV laser damage ability and break through the bottleneck of high power laser output at 355nm,laser pre-treatment have practical value in engineering.
2009, 33(3): 300-302.
Abstract:
Fast photoacoustic imaging systems,based on rotating multi-element linear transducer array,can improve the effect of asymmetric projection and reconstruct the photoacoustic image of complex absorbers.The simulation and experiments of photoacoustic images of rotating multi-element linear transducer array demonstrated that this kind of system could reconstruct images indicating the optical absorption distribution of absorbers.It will provides a novel and effective photoacoustic imaging approach for clinic diagnosis of neoplasm and tissue functional imaging in vivo,and has potential to be developed into a practical apparatus.
Fast photoacoustic imaging systems,based on rotating multi-element linear transducer array,can improve the effect of asymmetric projection and reconstruct the photoacoustic image of complex absorbers.The simulation and experiments of photoacoustic images of rotating multi-element linear transducer array demonstrated that this kind of system could reconstruct images indicating the optical absorption distribution of absorbers.It will provides a novel and effective photoacoustic imaging approach for clinic diagnosis of neoplasm and tissue functional imaging in vivo,and has potential to be developed into a practical apparatus.
2009, 33(3): 303-306,325.
Abstract:
Monitoring the vertical distribution of the aerosol with lidar is one of the focuses in the environment monitoring field.In order to study the vertical distribution of the air aerosol,a model to retrieve aerosol mass concentration was analyzed theoretic;aHy and proved experimentally.A modified model was presented based on exponent model and analysis of influence of the meteorological factors upon aerosol mass concentration.With the method of nonlinear least squares and some experience,some key parameters of the model and the vertical distribution of mass concentration can be retrieved.Conclusions are drawn as follows; the modified model can satisfactorily reflect the influence of meteorological factors upon aerosol mass concentration;the retrieved results consist with measured values.The results may be regarded as a reference to the research in this field.
Monitoring the vertical distribution of the aerosol with lidar is one of the focuses in the environment monitoring field.In order to study the vertical distribution of the air aerosol,a model to retrieve aerosol mass concentration was analyzed theoretic;aHy and proved experimentally.A modified model was presented based on exponent model and analysis of influence of the meteorological factors upon aerosol mass concentration.With the method of nonlinear least squares and some experience,some key parameters of the model and the vertical distribution of mass concentration can be retrieved.Conclusions are drawn as follows; the modified model can satisfactorily reflect the influence of meteorological factors upon aerosol mass concentration;the retrieved results consist with measured values.The results may be regarded as a reference to the research in this field.
2009, 33(3): 307-309,332.
Abstract:
In order to get the quantitative relationship between the decay time constant(DTC)of the laser-induced thermoelectric voltage(LITV)signals and the physical parameters of the thin films,YBa2Cu3O7-x,La0.67Ca0.33 MnO3, La0.67Ca0.33 MnO3 thin films were prepared by means of pulsed laser deposition.The corresponding LITV signals were detected with these films illuminated by 248nm pulsed laser.An exact function of DTC was deduced based on the interaction between the laser pulses and the films.The measured LITV signals were observed decaying exponentially,which is in agreement with the model of LITV effect.The DTC is just limited by the thermal transition properties of the films,and is the function of the thermal diffusion constant.According to the measured decay time,the thermal diffusion constants of the thin films can be calculated.Thus the measurement of DTC of LITV signals is a new way to investigate the thermal diffusion constant of thin films.
In order to get the quantitative relationship between the decay time constant(DTC)of the laser-induced thermoelectric voltage(LITV)signals and the physical parameters of the thin films,YBa2Cu3O7-x,La0.67Ca0.33 MnO3, La0.67Ca0.33 MnO3 thin films were prepared by means of pulsed laser deposition.The corresponding LITV signals were detected with these films illuminated by 248nm pulsed laser.An exact function of DTC was deduced based on the interaction between the laser pulses and the films.The measured LITV signals were observed decaying exponentially,which is in agreement with the model of LITV effect.The DTC is just limited by the thermal transition properties of the films,and is the function of the thermal diffusion constant.According to the measured decay time,the thermal diffusion constants of the thin films can be calculated.Thus the measurement of DTC of LITV signals is a new way to investigate the thermal diffusion constant of thin films.
2009, 33(3): 310-313.
Abstract:
In order to study the effect of Rochon prism on single-mode Gaussian beam,the interference in the cementing layer was analyzed in detail.The results reveal that for a given incident single-mode Gaussian beam,the intensity of transmitted polarizing light oscillates periodically with one of the three parameters,i.e.the incident angle at the interface of the cementing layer,the thickness and the refractive index of the cementing layer,and the shape of transmitted beam will be changed.Comparatively,the effect of prism on o light is less than a light.But in general,the effect on the transmitted Gaussian beam is lessthan 1%.
In order to study the effect of Rochon prism on single-mode Gaussian beam,the interference in the cementing layer was analyzed in detail.The results reveal that for a given incident single-mode Gaussian beam,the intensity of transmitted polarizing light oscillates periodically with one of the three parameters,i.e.the incident angle at the interface of the cementing layer,the thickness and the refractive index of the cementing layer,and the shape of transmitted beam will be changed.Comparatively,the effect of prism on o light is less than a light.But in general,the effect on the transmitted Gaussian beam is lessthan 1%.
2009, 33(3): 314-318,336.
Abstract:
With the aid of external optical injection,a novel all-optical logic gate based on Mach-Zehnder interferometer composed of semiconductor optical amplifier(SOA-M-ZI) was proposed.Meanwhile,by means of rate equations of the SOA,the logic AND gat was simulated and analyzed.As a result,the logic AND gate process signals with transmission speed of 10Gbit/s or below,and the external optical injection can effectively enhance the signal processing speed of SOA.It is useful to design all-optical logic gates based on SOA.
With the aid of external optical injection,a novel all-optical logic gate based on Mach-Zehnder interferometer composed of semiconductor optical amplifier(SOA-M-ZI) was proposed.Meanwhile,by means of rate equations of the SOA,the logic AND gat was simulated and analyzed.As a result,the logic AND gate process signals with transmission speed of 10Gbit/s or below,and the external optical injection can effectively enhance the signal processing speed of SOA.It is useful to design all-optical logic gates based on SOA.
2009, 33(3): 319-322.
Abstract:
The effect of misalignment of grating grooves on the output pulse width and temporal profiles was numerically simulated with ray-tracing method and Runge-Kutta method.When the angle of grating grooves is within the range of士4°,the pulse width induced by the original chirp becomes narrower if only considering group delay dispersion(GDD).However,the pulse width becomes broader than that of seed pulse when considering third order dispersion (TOD) or fourth order dispersion (FOD),even higher order dispersion.When the input pulse is with positive chirp,the pule width increases with the angle a continuously.However,when the input pulse is with negative chirp,the pulse width increases with the angle a first,and then decreases.The change of the pulse width is the same with grating G2 revolving clockwise or anti-clockwise.Furthermore,the original chirp makes the pre-pulse and post-pulse weaker.The effect of the negative chirp on pulse width and distortion is much weaker than that of the positive chirn.
The effect of misalignment of grating grooves on the output pulse width and temporal profiles was numerically simulated with ray-tracing method and Runge-Kutta method.When the angle of grating grooves is within the range of士4°,the pulse width induced by the original chirp becomes narrower if only considering group delay dispersion(GDD).However,the pulse width becomes broader than that of seed pulse when considering third order dispersion (TOD) or fourth order dispersion (FOD),even higher order dispersion.When the input pulse is with positive chirp,the pule width increases with the angle a continuously.However,when the input pulse is with negative chirp,the pulse width increases with the angle a first,and then decreases.The change of the pulse width is the same with grating G2 revolving clockwise or anti-clockwise.Furthermore,the original chirp makes the pre-pulse and post-pulse weaker.The effect of the negative chirp on pulse width and distortion is much weaker than that of the positive chirn.
2009, 33(3): 323-325.
Abstract:
The measurement precision of the fiber Bragg grating demodulator with a Fabry-Perot filter is not high enough because of noise.This light noise always leads to about lOpm of wavelength measurement error.Gaussian fitting of the reflected spectrum was proposed to eliminate the noise and improve the demodulation precision.Experiments proved that the wavelength error was less than 2.5 pm by means of Gaussian fitting when the standard deviation of the temperature was 0.3℃.It is proved by experiments that Gaussian fitting can be used to improve the wavelength measurement precision if there is not high noise in the system.
The measurement precision of the fiber Bragg grating demodulator with a Fabry-Perot filter is not high enough because of noise.This light noise always leads to about lOpm of wavelength measurement error.Gaussian fitting of the reflected spectrum was proposed to eliminate the noise and improve the demodulation precision.Experiments proved that the wavelength error was less than 2.5 pm by means of Gaussian fitting when the standard deviation of the temperature was 0.3℃.It is proved by experiments that Gaussian fitting can be used to improve the wavelength measurement precision if there is not high noise in the system.
2009, 33(3): 326-328.
Abstract:
In order to obtain the energy spectrum of high power ions in the interaction between laser and plasma,the Fokker-Planck equation,describing the isotropic electric particles,was solved.Then the effect of Langmuir plasmons in laser plasma and Langmuir turbulence spectrum on the ion acceleration was analyzed.The analytical results conformed to the experimental one and the energy spectrum attenuated exponentially.The results show that the realization of ion acceleration exist a great dependence on the style of Langmuir spectrum and only the Kolmogorov-type power-law spectrum is effective for ion acceleration.
In order to obtain the energy spectrum of high power ions in the interaction between laser and plasma,the Fokker-Planck equation,describing the isotropic electric particles,was solved.Then the effect of Langmuir plasmons in laser plasma and Langmuir turbulence spectrum on the ion acceleration was analyzed.The analytical results conformed to the experimental one and the energy spectrum attenuated exponentially.The results show that the realization of ion acceleration exist a great dependence on the style of Langmuir spectrum and only the Kolmogorov-type power-law spectrum is effective for ion acceleration.
2009, 33(3): 333-336.
Abstract:
In order to find a symmetrical dual-ridged waveguide with optimal transmission characteristics,two novel dual-ridged waveguides with circle and ellipse ridges respectively were put forward.The influence of both the deformed dual-ridged waveguides on the transmission characteristics of the waveguide was analyzed by means of finite element method.The cut off wavelength and single-mode bandwidth were calculated for different ridge dimensions.The field patterns of dominant mode and the curve for the effect of deformation on the cutoff wavelength and brand width were drawn.Finally,the relationship between the transmission characteristics and the dimension of the ridges was analyzed.It is shown that these results can provide valuable reference of application and study of the deformed dual-ridge waveguides and provide instructions for miniaturization of ridged waveguide apparatus.
In order to find a symmetrical dual-ridged waveguide with optimal transmission characteristics,two novel dual-ridged waveguides with circle and ellipse ridges respectively were put forward.The influence of both the deformed dual-ridged waveguides on the transmission characteristics of the waveguide was analyzed by means of finite element method.The cut off wavelength and single-mode bandwidth were calculated for different ridge dimensions.The field patterns of dominant mode and the curve for the effect of deformation on the cutoff wavelength and brand width were drawn.Finally,the relationship between the transmission characteristics and the dimension of the ridges was analyzed.It is shown that these results can provide valuable reference of application and study of the deformed dual-ridge waveguides and provide instructions for miniaturization of ridged waveguide apparatus.
2009, 33(3): 329-332.
Abstract:
In order to show the best information of monochromatic remote sensing images,it was processed with the algorithms of wavelet transform,advanced mufti-scale Retinex,and homomorphic filter respectively.The criterions of brightness,contrast degree,production of brightness multiplying with contrast degree,information entropy,fidelity were applied to evaluate the quality for the images enhanced by 7 methods and original images.The results showed 3 points.Firstly,the values of brightness,contrast,and production of brightness multiplying with contrast were largest and their image quality was best when the images handled by mufti-scale Retinex and stretched the range of k=1 time standard deviation near the mean brightness.Secondly,the values of contrast and information entropy were biggest and their image quality was well when the images handled by wavelet transform with a high-pass filter.Finally,the value of fidelity was largest in all algorithms and their image quality was common when the images handled by homomorphic filter with n=1.The algorithms of advanced mufti-scale Retinex and wavelet transform were best for removing black cloud and white cloud in remote sensing images respectively.
In order to show the best information of monochromatic remote sensing images,it was processed with the algorithms of wavelet transform,advanced mufti-scale Retinex,and homomorphic filter respectively.The criterions of brightness,contrast degree,production of brightness multiplying with contrast degree,information entropy,fidelity were applied to evaluate the quality for the images enhanced by 7 methods and original images.The results showed 3 points.Firstly,the values of brightness,contrast,and production of brightness multiplying with contrast were largest and their image quality was best when the images handled by mufti-scale Retinex and stretched the range of k=1 time standard deviation near the mean brightness.Secondly,the values of contrast and information entropy were biggest and their image quality was well when the images handled by wavelet transform with a high-pass filter.Finally,the value of fidelity was largest in all algorithms and their image quality was common when the images handled by homomorphic filter with n=1.The algorithms of advanced mufti-scale Retinex and wavelet transform were best for removing black cloud and white cloud in remote sensing images respectively.
