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RSS2006 Vol. 30, No. 2
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2006, 30(2): 113-115,122.
[Abstract]
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Abstract:
To make the CuBr vapour lasers work efficiently and stably,the orthonormal design of experiments is used to test the optimization of the parameters of the discharge circuit in the laser power supply.The optimum set of parameters is found.
To make the CuBr vapour lasers work efficiently and stably,the orthonormal design of experiments is used to test the optimization of the parameters of the discharge circuit in the laser power supply.The optimum set of parameters is found.
2006, 30(2): 116-118.
Abstract:
A new flexible solidstate laser power supply based on CUK converter with high performance is presented.The principle of the power supply system is analysed and the schematic diagram of the circuit is provided.Experiments prove the power system has good electrical character,flexibility and reliability.
A new flexible solidstate laser power supply based on CUK converter with high performance is presented.The principle of the power supply system is analysed and the schematic diagram of the circuit is provided.Experiments prove the power system has good electrical character,flexibility and reliability.
2006, 30(2): 119-122.
Abstract:
Based on considering kinetic evolution of the emissions of both ions,the basic processes of energy transfer between thulium(Tm) and holmium(Ho) was analyzed,the quasi-four-level rate equation of thulium(Tm)/holmium(Ho) doped gadolinium vanadate(Tm/Ho:GdVO4) are given.The expression about threshold pump power and slope efficiency are concluded.At liquid nitrogen cooled temperature the operation of 2μm Tm/Ho:GdVO4 laser end-pumped by fiber-coupled laser diode(LD) is achieved experimentally.At 14W pump power the maximum 3.5W output power,optical-optical conversion efficiency of 25%,slope efficiency of 26.6% and pumping threshold of 838mW were obtained,theoretical results with experiment results are good agreement.The observed green fluorescence duo to result of up-conversion effect is also analyzed.
Based on considering kinetic evolution of the emissions of both ions,the basic processes of energy transfer between thulium(Tm) and holmium(Ho) was analyzed,the quasi-four-level rate equation of thulium(Tm)/holmium(Ho) doped gadolinium vanadate(Tm/Ho:GdVO4) are given.The expression about threshold pump power and slope efficiency are concluded.At liquid nitrogen cooled temperature the operation of 2μm Tm/Ho:GdVO4 laser end-pumped by fiber-coupled laser diode(LD) is achieved experimentally.At 14W pump power the maximum 3.5W output power,optical-optical conversion efficiency of 25%,slope efficiency of 26.6% and pumping threshold of 838mW were obtained,theoretical results with experiment results are good agreement.The observed green fluorescence duo to result of up-conversion effect is also analyzed.
2006, 30(2): 123-125.
Abstract:
The quantity value of signal and background light of fluorescence imaging system of nasopharyngeal carcinoma is calculated when photosensitizer is excited by the light at the wavelength of 488nm.In order to distinguish the signal from the background light,the light-transmission coefficient of a narrow-band filter must be as great as possible and noise must be reduced by a factor of 4.3×10-5.According to the absorption characteristic of colored glass,the ratio of signal transmission coefficient to background light transmission becomes large with optical-path increased suitably.If the thickness of the colored glass and the band width of the narrow-band filter now on hand is encreased properly,fine signal-to-noise ratio and resolving capability of fluorescence imaging can be obtained.
The quantity value of signal and background light of fluorescence imaging system of nasopharyngeal carcinoma is calculated when photosensitizer is excited by the light at the wavelength of 488nm.In order to distinguish the signal from the background light,the light-transmission coefficient of a narrow-band filter must be as great as possible and noise must be reduced by a factor of 4.3×10-5.According to the absorption characteristic of colored glass,the ratio of signal transmission coefficient to background light transmission becomes large with optical-path increased suitably.If the thickness of the colored glass and the band width of the narrow-band filter now on hand is encreased properly,fine signal-to-noise ratio and resolving capability of fluorescence imaging can be obtained.
2006, 30(2): 126-129.
Abstract:
Demodulated by fiber optic Mach-Zehnder interferometer which has longer unbalance length,the sensing signal of DFB laser experiences the polarization induced fading.The feedback control scheme of interferometer input light polarization is introduced,which can be used to overcome the polarization induced fading.The interferometer signal demodulation system is discussed in detail,which has feedback control function.The relation between control signal and interferometer stripe visibility is deduced.The working process is analysed at different signal input condition.Theoretically the interference stripe visibility can be stabilized nearby 1 under a certain condition.The feedback control scheme can be used to eliminate the polarization induced fading.
Demodulated by fiber optic Mach-Zehnder interferometer which has longer unbalance length,the sensing signal of DFB laser experiences the polarization induced fading.The feedback control scheme of interferometer input light polarization is introduced,which can be used to overcome the polarization induced fading.The interferometer signal demodulation system is discussed in detail,which has feedback control function.The relation between control signal and interferometer stripe visibility is deduced.The working process is analysed at different signal input condition.Theoretically the interference stripe visibility can be stabilized nearby 1 under a certain condition.The feedback control scheme can be used to eliminate the polarization induced fading.
2006, 30(2): 130-132,160.
Abstract:
Some tensile samples of stainless steel have been fabricated directly by laser cladding with three path-filling models.The results show that the fracture character of tensile samples with high bond strength is ductile rupture,and the yielded strength and rupture strength are higher than the corresponding values of samples with the conventional processing methods.The orientation of laser scanning has no significant influence on tensile performance.Microstructure analyses of tensile samples by SEM show that crystalline grains are very fine and have the orientated solidification structures.
Some tensile samples of stainless steel have been fabricated directly by laser cladding with three path-filling models.The results show that the fracture character of tensile samples with high bond strength is ductile rupture,and the yielded strength and rupture strength are higher than the corresponding values of samples with the conventional processing methods.The orientation of laser scanning has no significant influence on tensile performance.Microstructure analyses of tensile samples by SEM show that crystalline grains are very fine and have the orientated solidification structures.
2006, 30(2): 133-135,167.
Abstract:
Laser cavity stability is a conventional and concerning subject from the birth of laser.With a "cat's eye" reflector as the reflecting mirror,the problems of laser adjustment and power stability can be solved.Comprehensive experiments are carried out in a half-external cavity He-Ne laser and the "cat's eye" reflector cavity,plane-concave mirror cavity and concave-concave mirror cavity.The results show that the use of the half-external "cat's eye" cavity can improve the laser stability and lower the power drift significantly.The adjustment problem is also considered and solved.A stable and adjustment-free He-Ne laser is finally realized,which exhibits remarkable advantages than the current He-Ne lasers.
Laser cavity stability is a conventional and concerning subject from the birth of laser.With a "cat's eye" reflector as the reflecting mirror,the problems of laser adjustment and power stability can be solved.Comprehensive experiments are carried out in a half-external cavity He-Ne laser and the "cat's eye" reflector cavity,plane-concave mirror cavity and concave-concave mirror cavity.The results show that the use of the half-external "cat's eye" cavity can improve the laser stability and lower the power drift significantly.The adjustment problem is also considered and solved.A stable and adjustment-free He-Ne laser is finally realized,which exhibits remarkable advantages than the current He-Ne lasers.
2006, 30(2): 136-137,141.
Abstract:
Adopting noise-initiation mode of stimulated Brillouin scattering(SBS),the transient SBS equations are numerically solved,and the intensity distribution of transmission beam when the Gaussian beam passes Brillouin medium is simulated.The results indicate that the peak intensity of transmission beam is limited,and the cross-section intensity distribution is approximately flat-topped super Gaussian,which shows the optical limiting effect of SBS.When the interaction length or gain coefficient is changed,the SBS threshold is changed,and the intensity value of optical limiting is altered.
Adopting noise-initiation mode of stimulated Brillouin scattering(SBS),the transient SBS equations are numerically solved,and the intensity distribution of transmission beam when the Gaussian beam passes Brillouin medium is simulated.The results indicate that the peak intensity of transmission beam is limited,and the cross-section intensity distribution is approximately flat-topped super Gaussian,which shows the optical limiting effect of SBS.When the interaction length or gain coefficient is changed,the SBS threshold is changed,and the intensity value of optical limiting is altered.
2006, 30(2): 138-141.
Abstract:
Theoretical model of Tm3+,Ho3+ co-doped silica fiber laser pumped at 1200nm band is established,then its performance is studied by numerical simulation,and the theoretical and experimental results are compared,in order to seek the space to optimize the performance of this fiber laser.The computated output power of 1.14W and 733mW are slightly higher than the experimental values of 930mW and 650mW,respectively,whether radiation occurs only Tm3+ between the 3H4 and 3H6 level(with a fiber length of 1m) or energy transfer takes place between Tm3+ and Ho3+(with a fiber length of 3m),with a maximum launched pump power of 3.1W.The computed value is more consistent with the experimental one when energy transfer takes place between Tm3+ and Ho3+.
Theoretical model of Tm3+,Ho3+ co-doped silica fiber laser pumped at 1200nm band is established,then its performance is studied by numerical simulation,and the theoretical and experimental results are compared,in order to seek the space to optimize the performance of this fiber laser.The computated output power of 1.14W and 733mW are slightly higher than the experimental values of 930mW and 650mW,respectively,whether radiation occurs only Tm3+ between the 3H4 and 3H6 level(with a fiber length of 1m) or energy transfer takes place between Tm3+ and Ho3+(with a fiber length of 3m),with a maximum launched pump power of 3.1W.The computed value is more consistent with the experimental one when energy transfer takes place between Tm3+ and Ho3+.
2006, 30(2): 142-144,147.
Abstract:
Starting from the polarization matrix and propagation equation of the cross-spectral density matrix,a detailed study of the influence of hard-edge aperture on the spectral switch of polychromatic vector Gaussian-Schell model beams is performed.It is shown that before inserting a polarizer the transition height Δ of the spectral switch decreases,the minimum Smin and the critical position zc/z0 increase as the truncation parameter δ increases.After inserting the polarizer,the spectral switch varies with the truncation parameter δ in a similar way as the case without the polarizer.However,the polarization angle θ affects the range of the truncation parameter δ at which the spectral switch appears.
Starting from the polarization matrix and propagation equation of the cross-spectral density matrix,a detailed study of the influence of hard-edge aperture on the spectral switch of polychromatic vector Gaussian-Schell model beams is performed.It is shown that before inserting a polarizer the transition height Δ of the spectral switch decreases,the minimum Smin and the critical position zc/z0 increase as the truncation parameter δ increases.After inserting the polarizer,the spectral switch varies with the truncation parameter δ in a similar way as the case without the polarizer.However,the polarization angle θ affects the range of the truncation parameter δ at which the spectral switch appears.
2006, 30(2): 145-147.
Abstract:
In laser beam welding,an appropriate crossjet nozzle should be mounted under the welding head in order to protect the optics from the welding spatter and smoke.An ultrasonic crossjet with a non-symmetric Laval cavity is designed based on the aerodynamic theory.Schlieren trial show that a rigid flow with a small divergence is obtained,and no disturbing near the flow can be observed.Welding experiments prove that focusing mirror is well protected when such a crossjet is used.
In laser beam welding,an appropriate crossjet nozzle should be mounted under the welding head in order to protect the optics from the welding spatter and smoke.An ultrasonic crossjet with a non-symmetric Laval cavity is designed based on the aerodynamic theory.Schlieren trial show that a rigid flow with a small divergence is obtained,and no disturbing near the flow can be observed.Welding experiments prove that focusing mirror is well protected when such a crossjet is used.
2006, 30(2): 148-151,154.
Abstract:
A double-pass forward pumping(DPFP) broadband Er3+/Yb3+ co-doped superfluorescent fiber source at(1.55μm) is demonstrated and experimentally investigated.The output power,mean wavelength and bandwidth of the source are studied on three different length fibers when pumped near 976nm and operated in their optimal pump power.The experimental results show that the fiber source of a 60cm Er3+/Yb3+ co-doped fiber behaves better than the others.A maximum output power of 9.18mW and a bandwidth of only 34nm are achieved simultaneously with mean wavelength stability of 7.16×10-6m/mW.If decreasing the output power to about 3.78mW,a maximum bandwidth of more than 80nm can be acquired.
A double-pass forward pumping(DPFP) broadband Er3+/Yb3+ co-doped superfluorescent fiber source at(1.55μm) is demonstrated and experimentally investigated.The output power,mean wavelength and bandwidth of the source are studied on three different length fibers when pumped near 976nm and operated in their optimal pump power.The experimental results show that the fiber source of a 60cm Er3+/Yb3+ co-doped fiber behaves better than the others.A maximum output power of 9.18mW and a bandwidth of only 34nm are achieved simultaneously with mean wavelength stability of 7.16×10-6m/mW.If decreasing the output power to about 3.78mW,a maximum bandwidth of more than 80nm can be acquired.
2006, 30(2): 152-154.
Abstract:
Using the relations between Hermite and Laguerre-Gaussian(LG) modes and expanding the window function of two-dimensional rectangular hard-edged apertures into a finite sum of complex Gaussian functions,the propagation of complex-argument Laguerre-Gaussian beams through a paraxial optical ABCD system with a rectangular hard-edged aperture is studied.An analytical propagation equation is derived and used to study the diffraction at the rectangular hard-edged aperture and the focusing properties of complex-argument LG beams.The method proposed is useful for studying the beam transformation through an apertured optical system with different geometrical symmetry.
Using the relations between Hermite and Laguerre-Gaussian(LG) modes and expanding the window function of two-dimensional rectangular hard-edged apertures into a finite sum of complex Gaussian functions,the propagation of complex-argument Laguerre-Gaussian beams through a paraxial optical ABCD system with a rectangular hard-edged aperture is studied.An analytical propagation equation is derived and used to study the diffraction at the rectangular hard-edged aperture and the focusing properties of complex-argument LG beams.The method proposed is useful for studying the beam transformation through an apertured optical system with different geometrical symmetry.
2006, 30(2): 155-157.
Abstract:
A new heterocycle compound is studied with z-scan technique.The compound is a conjugate with metal atom in the center with π electronic structure.Under the CW 488nm laser excitation,the compound shows the selfdefocus property,and its third-order optical nonlinear polarization index in dichloro-methane solution is measured-1.33×10-4 esu.Besides,the optical limiting property of the compound is also investigated preliminarily based on the above experiment result.For 488nm wavelength light source,its optical limiting threshold is 25W/cm2,and the limiting mechanism should be the reverse saturable absorption effect of the excited states.All the results show that this compound have a bright future in nonlinear optical application field.
A new heterocycle compound is studied with z-scan technique.The compound is a conjugate with metal atom in the center with π electronic structure.Under the CW 488nm laser excitation,the compound shows the selfdefocus property,and its third-order optical nonlinear polarization index in dichloro-methane solution is measured-1.33×10-4 esu.Besides,the optical limiting property of the compound is also investigated preliminarily based on the above experiment result.For 488nm wavelength light source,its optical limiting threshold is 25W/cm2,and the limiting mechanism should be the reverse saturable absorption effect of the excited states.All the results show that this compound have a bright future in nonlinear optical application field.
2006, 30(2): 158-160.
Abstract:
A novel scheme for generating dual-wavelength low timing jitter tunable ultra-short pulses is demonstrated.Injecting the external seeding source to the gain-switched F-P laser diode,a reduction of timing jitter and a tunable dual-wavelength spectrum is achieved.Two multiple quantum-well DFB laser diodes are used as the external-injection seeding source.Adjusting the temperature of the laser diodes and the polarization of the seeding source,the injection seeding source is coupled with the F-P laser diode effectively.A reduction of timing jitter(root-mean-square) from 2.57ps to 1.06ps is achieved,and the output side-mode-suppression-ratio is larger than 25dB.Changing the temperature of the laser diodes,a tunable range from 1540nm to 1560nm is achieved.
A novel scheme for generating dual-wavelength low timing jitter tunable ultra-short pulses is demonstrated.Injecting the external seeding source to the gain-switched F-P laser diode,a reduction of timing jitter and a tunable dual-wavelength spectrum is achieved.Two multiple quantum-well DFB laser diodes are used as the external-injection seeding source.Adjusting the temperature of the laser diodes and the polarization of the seeding source,the injection seeding source is coupled with the F-P laser diode effectively.A reduction of timing jitter(root-mean-square) from 2.57ps to 1.06ps is achieved,and the output side-mode-suppression-ratio is larger than 25dB.Changing the temperature of the laser diodes,a tunable range from 1540nm to 1560nm is achieved.
2006, 30(2): 165-167.
Abstract:
Because the isolation performance of Raman filter is not high,a new demodulation method is proposed to suppress the system background noise,heat excursion accumulation and anti-Stokes backward scattering intermingled with Rayleigh backward scattering.The new method can improve the temperature precision,stability and sensitivity of system and reduce the system cost with the constant temperature groove abrogated.The experimental results show its measurement precision is better than 0.05℃.
Because the isolation performance of Raman filter is not high,a new demodulation method is proposed to suppress the system background noise,heat excursion accumulation and anti-Stokes backward scattering intermingled with Rayleigh backward scattering.The new method can improve the temperature precision,stability and sensitivity of system and reduce the system cost with the constant temperature groove abrogated.The experimental results show its measurement precision is better than 0.05℃.
2006, 30(2): 168-169,180.
Abstract:
There exist a series of complicated physicochemical changes in the composite reinforced by polyaryl amide fibers irradiated by laser.The damage configuration and physicochemical process of different laser parameters are obtained through the micro-analysis of the recovery samples after experiments.Thermal damage relies on the chemical changes critically.
There exist a series of complicated physicochemical changes in the composite reinforced by polyaryl amide fibers irradiated by laser.The damage configuration and physicochemical process of different laser parameters are obtained through the micro-analysis of the recovery samples after experiments.Thermal damage relies on the chemical changes critically.
2006, 30(2): 170-173.
Abstract:
The system structure,the theory and the technical parameters for a 1064nm Mie-scattering micropulse lidar are presented.Based on the experimental results,the overlap factor of the system and retrieve the profile of the atmosphere aerosol extinction coefficient can be deduced.Signals can be detected by the lidar system about 5km far away at night.The 3-D profile of the extinction varied with altitude and time can be received by lidar's day and night surveying,which helps to study the thickness,distribution,scatter and absoption of the atmospheric aerosol.
The system structure,the theory and the technical parameters for a 1064nm Mie-scattering micropulse lidar are presented.Based on the experimental results,the overlap factor of the system and retrieve the profile of the atmosphere aerosol extinction coefficient can be deduced.Signals can be detected by the lidar system about 5km far away at night.The 3-D profile of the extinction varied with altitude and time can be received by lidar's day and night surveying,which helps to study the thickness,distribution,scatter and absoption of the atmospheric aerosol.
2006, 30(2): 174-176.
Abstract:
The vertical distribution of aerosol scattering ratios and extinction coefficients over the observation site at Beijing and Naqu are shown,the correlation of extinction coefficient and wind speed are also discussed,and the conclusions are drawn: the distributions and concentrations of aerosol at Beijing are more sophisticated than that at Naqu,the ambient air quality at Naqu is purer than that at Beijing,and the layer is lower than that at Beijing,etc.
The vertical distribution of aerosol scattering ratios and extinction coefficients over the observation site at Beijing and Naqu are shown,the correlation of extinction coefficient and wind speed are also discussed,and the conclusions are drawn: the distributions and concentrations of aerosol at Beijing are more sophisticated than that at Naqu,the ambient air quality at Naqu is purer than that at Beijing,and the layer is lower than that at Beijing,etc.
2006, 30(2): 177-180.
Abstract:
The finite element model of the thermal conductive equation and the thermo-elastic equation in the system consisting of a transparent coating and a opaque substrate is established based on the analysis of the stability of solution and two important parameters,meshing size and time step.Taking into account the temperature dependence of material properties,the transient temperature is obtained.The near-axis normal waveforms at the epicenter generated by thermo-elastic effect are obtained.The influence of the coating thickness on the waveform is analyzed.
The finite element model of the thermal conductive equation and the thermo-elastic equation in the system consisting of a transparent coating and a opaque substrate is established based on the analysis of the stability of solution and two important parameters,meshing size and time step.Taking into account the temperature dependence of material properties,the transient temperature is obtained.The near-axis normal waveforms at the epicenter generated by thermo-elastic effect are obtained.The influence of the coating thickness on the waveform is analyzed.
2006, 30(2): 181-182,185.
Abstract:
Based on the second-order moment of the power density,the far-field divergence angle of nonparaxial rotationally symmetric Laguerre-Gaussian(LG) beams is derived and expressed in a sum of the series of the Gamma function.It is shown that the far-field divergence angle of nonparaxial rotationally LG beams approaches to an asymptotic value of 63.435° as the initial waist-width to wavelength ratio w0/λ approaches zero,which is independent of the order.For the special case of p=0 our result reduces to that of nonparaxial Gaussian beams.
Based on the second-order moment of the power density,the far-field divergence angle of nonparaxial rotationally symmetric Laguerre-Gaussian(LG) beams is derived and expressed in a sum of the series of the Gamma function.It is shown that the far-field divergence angle of nonparaxial rotationally LG beams approaches to an asymptotic value of 63.435° as the initial waist-width to wavelength ratio w0/λ approaches zero,which is independent of the order.For the special case of p=0 our result reduces to that of nonparaxial Gaussian beams.
2006, 30(2): 183-185.
Abstract:
An experiment set-up is constructed to measure the transverse velocity of a moving target by using dual beam mode of CW CO2 laser in the laboratory.The experiment is conducted in the laboratory using dual-beam mode and clear Doppler frequency signals are recorded,and signal data filtering is performed leading to an enhanced SNR.The calculated velocity of the moving target is compared with the actual velocity.The result shows that the measured velocity corresponds with the actual velocity very well.
An experiment set-up is constructed to measure the transverse velocity of a moving target by using dual beam mode of CW CO2 laser in the laboratory.The experiment is conducted in the laboratory using dual-beam mode and clear Doppler frequency signals are recorded,and signal data filtering is performed leading to an enhanced SNR.The calculated velocity of the moving target is compared with the actual velocity.The result shows that the measured velocity corresponds with the actual velocity very well.
2006, 30(2): 186-188,191.
Abstract:
Based on some numerical techniques such as split-step Fourier transformation,fourth-order Runge-Kutta and iteration method,the method for solving the inverse problem of monochromatic third-harmonic generation,i.e.the fundamental field is calculated from the given third-harmonic field,is proposed.The numerical calculation is performed and analyzed.The effects of the initial fields on the time and the precision of the iterative calculation are also discussed.It can be shown that our method is available and efficient.
Based on some numerical techniques such as split-step Fourier transformation,fourth-order Runge-Kutta and iteration method,the method for solving the inverse problem of monochromatic third-harmonic generation,i.e.the fundamental field is calculated from the given third-harmonic field,is proposed.The numerical calculation is performed and analyzed.The effects of the initial fields on the time and the precision of the iterative calculation are also discussed.It can be shown that our method is available and efficient.
2006, 30(2): 189-191.
Abstract:
Planar optical waveguides in glass have been fabricated with field-assisted ion exchange and thermal ion exchange technology.The results show that the refractive profiles of the waveguids are different with the abve two methods.A waveguide with step-index profile has been got using field-assisted ion exchange technology while a variable index profile waveguide has been obtained with the latter method.The numerical results show that the optical waveguide with step-index profile fabricated by electric field-assisted ion exchange technology confines the optical field better.It has more advantages to fabricate active optical devices and integrated optical devices.
Planar optical waveguides in glass have been fabricated with field-assisted ion exchange and thermal ion exchange technology.The results show that the refractive profiles of the waveguids are different with the abve two methods.A waveguide with step-index profile has been got using field-assisted ion exchange technology while a variable index profile waveguide has been obtained with the latter method.The numerical results show that the optical waveguide with step-index profile fabricated by electric field-assisted ion exchange technology confines the optical field better.It has more advantages to fabricate active optical devices and integrated optical devices.
2006, 30(2): 192-194.
Abstract:
1.57μm OPO laser is designed to meet project needs.OPO lasers are realized with Cr4+:YAG passive Q-switch for two different unstable cavities.Under the power supply of 7J,laser output at 1.57μm is attained with high beam quality.For one of the cavities,the laser output energy and divergence are 6mJ and 3.0mard respectively.For the other cavity,4mJ and(3.0mrad.)The difficulty of poor beam quality of OPO is overcome with the simple and compact structure.
1.57μm OPO laser is designed to meet project needs.OPO lasers are realized with Cr4+:YAG passive Q-switch for two different unstable cavities.Under the power supply of 7J,laser output at 1.57μm is attained with high beam quality.For one of the cavities,the laser output energy and divergence are 6mJ and 3.0mard respectively.For the other cavity,4mJ and(3.0mrad.)The difficulty of poor beam quality of OPO is overcome with the simple and compact structure.
2006, 30(2): 198-201.
Abstract:
The operation principal of Er3+,Tm3+ co-doped silica fiber amplifier is presented when pumped at 980nm.Depending on the principal,the mathematical model of energy transfer process between Er3+ and Tm3+ ions is established.Based on the rate and propagation equations,numerical simulation of its steady state operation properties is performed and the simulation of output power spectrum of several channel signals as a function of different factors,(such as different fiber length,different pump power,and different Tm3+ ions concentration) is also given.The simulation results show that the amplifying bandwidth of this fiber is up to 90nm(twice larger than the traditional Er-doped fiber amplifier) and the average gain is up to 10dB when the pump power is just 400mW.Its characteristic of ultra-wide band amplifying is useful for DWDM in the near future.
The operation principal of Er3+,Tm3+ co-doped silica fiber amplifier is presented when pumped at 980nm.Depending on the principal,the mathematical model of energy transfer process between Er3+ and Tm3+ ions is established.Based on the rate and propagation equations,numerical simulation of its steady state operation properties is performed and the simulation of output power spectrum of several channel signals as a function of different factors,(such as different fiber length,different pump power,and different Tm3+ ions concentration) is also given.The simulation results show that the amplifying bandwidth of this fiber is up to 90nm(twice larger than the traditional Er-doped fiber amplifier) and the average gain is up to 10dB when the pump power is just 400mW.Its characteristic of ultra-wide band amplifying is useful for DWDM in the near future.
2006, 30(2): 202-205.
Abstract:
Starting from the nonlinear Schrdinger equation describing the pulse propagation in erbium-doped fiber amplifier(EDFA),the compression and amplification of fundamental soliton pulse using EDFA are investigated numerically,and the optimum schemes for soliton pulse compression are proposed.The results show that:for the fundamental soliton pulse without the chirp,the pulse can be compressed and amplified adiabatically by selecting appropriate parameters of erbium-doped fibers;for the chirped fundamental soliton pulse,the process of the compression and amplification is not satisfied adiabatical condition;the effective compression and amplification can be obtained for the positive chirped fundamental soliton pulse,but the compression effect for the negative chirped fundamental soliton pulse is poor.
Starting from the nonlinear Schrdinger equation describing the pulse propagation in erbium-doped fiber amplifier(EDFA),the compression and amplification of fundamental soliton pulse using EDFA are investigated numerically,and the optimum schemes for soliton pulse compression are proposed.The results show that:for the fundamental soliton pulse without the chirp,the pulse can be compressed and amplified adiabatically by selecting appropriate parameters of erbium-doped fibers;for the chirped fundamental soliton pulse,the process of the compression and amplification is not satisfied adiabatical condition;the effective compression and amplification can be obtained for the positive chirped fundamental soliton pulse,but the compression effect for the negative chirped fundamental soliton pulse is poor.
2006, 30(2): 206-208.
Abstract:
Actively mode-locked fiber lasers based on the semiconductor optical amplifier(SOA),which are capable of generating ultra-short pulse train with high quality and high repetition rates,have received considerable attention.After considering the facet reflectively of the SOA,a theoretical model of the harmonic mode-locked fiber ring laser based on SOA is established.Based on this model,the influence of the facet residual reflectivity on the shape,peak power,and pulse width of the pulse output from the harmonic mode-locked fiber ring laser is studied.The results show the residual facet reflectivity of the SOA affects seriously the shape of the mode-locked pulse.With the increase of the facet reflectively of the SOA,the peak power of the mode-locked pulse will be increased and the mode-locked pulse will be broaden.
Actively mode-locked fiber lasers based on the semiconductor optical amplifier(SOA),which are capable of generating ultra-short pulse train with high quality and high repetition rates,have received considerable attention.After considering the facet reflectively of the SOA,a theoretical model of the harmonic mode-locked fiber ring laser based on SOA is established.Based on this model,the influence of the facet residual reflectivity on the shape,peak power,and pulse width of the pulse output from the harmonic mode-locked fiber ring laser is studied.The results show the residual facet reflectivity of the SOA affects seriously the shape of the mode-locked pulse.With the increase of the facet reflectively of the SOA,the peak power of the mode-locked pulse will be increased and the mode-locked pulse will be broaden.
2006, 30(2): 209-211,220.
Abstract:
Based on the nonlinear Schrdinger equation used to describe the normalized amplitude evolution in the fiber,the influence of the third-order dispersion on the transmission characteristics of super-Gaussian optical pulse with different chirps in the fiber is studied numerically.The results show that the peak intensity of super-Gaussian optical pulse becomes higher at the beginning,and the tail experiences a process of strengthening,and then weakening,which are different from Gaussian optical pulse.The results also show that the initial chirps will strengthen the influence of the third-order dispersion,so the method to compensate the influence of dispersion by adjusting the initial chirps should be used carefully in the case that the influence of the third-order dispersion can't be ignored.
Based on the nonlinear Schrdinger equation used to describe the normalized amplitude evolution in the fiber,the influence of the third-order dispersion on the transmission characteristics of super-Gaussian optical pulse with different chirps in the fiber is studied numerically.The results show that the peak intensity of super-Gaussian optical pulse becomes higher at the beginning,and the tail experiences a process of strengthening,and then weakening,which are different from Gaussian optical pulse.The results also show that the initial chirps will strengthen the influence of the third-order dispersion,so the method to compensate the influence of dispersion by adjusting the initial chirps should be used carefully in the case that the influence of the third-order dispersion can't be ignored.
2006, 30(2): 212-214,224.
Abstract:
Based on the optical systems' "cat' s eye" effect,a new technique working with single frequency modulated CW laser against IR scanning imaging systems is provided.The retrodirective reflection of the optical systems against the incident laser is discussed and based on the analysis of echo signals' characteristics.A digital quadrature coherent detector is used to detect such signals with low S/N ratio and the expected results is obtained in experiments.
Based on the optical systems' "cat' s eye" effect,a new technique working with single frequency modulated CW laser against IR scanning imaging systems is provided.The retrodirective reflection of the optical systems against the incident laser is discussed and based on the analysis of echo signals' characteristics.A digital quadrature coherent detector is used to detect such signals with low S/N ratio and the expected results is obtained in experiments.
2006, 30(2): 215-217.
Abstract:
In order to verify whether the thickness of air-gap would influence the prism's transmittance,the transmittance of Glan-Taylor prism and Glan-Faucault prism is theoretically studied.The transmittance of two-Glan-Taylor prisms and two-Glan-Faucault prisms is tested with a UV-3101 spectral photometer,and the results are found the transmittance of Glan-Taylor prism(about 85%) is obviously higher than that of Glan-Faucault prism(about 50%).For strictly collimating light,the transmittance of these two types of prism varies with the wavelength change,and this vibration is stronger for Glan-Faucault prism than for Glan-Taylor prism.However,the experimental result tested by spectral photometer doesn't have vibration,which shows that for non-strictly collimating light,the thickness of air-gap doesn't influence the prism's transmittance.
In order to verify whether the thickness of air-gap would influence the prism's transmittance,the transmittance of Glan-Taylor prism and Glan-Faucault prism is theoretically studied.The transmittance of two-Glan-Taylor prisms and two-Glan-Faucault prisms is tested with a UV-3101 spectral photometer,and the results are found the transmittance of Glan-Taylor prism(about 85%) is obviously higher than that of Glan-Faucault prism(about 50%).For strictly collimating light,the transmittance of these two types of prism varies with the wavelength change,and this vibration is stronger for Glan-Faucault prism than for Glan-Taylor prism.However,the experimental result tested by spectral photometer doesn't have vibration,which shows that for non-strictly collimating light,the thickness of air-gap doesn't influence the prism's transmittance.
2006, 30(2): 218-220.
Abstract:
The purpose is to describe the design and the construction of a no-flow conventional CW CO2 laser with line selected by concave grating.In order to obtain the lines at 11μm wavelength region,a concave grating(150lines/mm,blazed at 10.6μm) with a 10m radius curvature and a longer cavity(4.5m) is employed to increase the resolution of the cavity without a hot CO2 absorption cell in the cavity.In this laser,besides more than 100 laser lines observed from R(56) to P(56) in the regular 0001-[1000,0200]Ⅰ,Ⅱ band,another 16 lines in 11μm wavelength region including 7 lines in the 0111-0310 band,1 line in the 0011-1110 band,5 lines in the isotope C13O2160001-1000 band and 3 lines in the isotope C13O2180001-1000 band,are also observed.The output power of every line is above 1.6W.
The purpose is to describe the design and the construction of a no-flow conventional CW CO2 laser with line selected by concave grating.In order to obtain the lines at 11μm wavelength region,a concave grating(150lines/mm,blazed at 10.6μm) with a 10m radius curvature and a longer cavity(4.5m) is employed to increase the resolution of the cavity without a hot CO2 absorption cell in the cavity.In this laser,besides more than 100 laser lines observed from R(56) to P(56) in the regular 0001-[1000,0200]Ⅰ,Ⅱ band,another 16 lines in 11μm wavelength region including 7 lines in the 0111-0310 band,1 line in the 0011-1110 band,5 lines in the isotope C13O2160001-1000 band and 3 lines in the isotope C13O2180001-1000 band,are also observed.The output power of every line is above 1.6W.
2006, 30(2): 221-224.
Abstract:
A camera calibration method with co-line points is proposed,in which distortion center is located according to cross ratio invariability,and then distortion coefficients are calculated based on a line's central projection is a line.The emulation indicates that only if some measures are adopted to decrease the projection points' coordinate error,error of the distortion center would be less than 2 pixels and relative error of the distortion coefficients would be no more than 0.1.The experiment shows that these distortion parameters gained with the proposed method are good at a correcting distortion image.Because of its easiness and simplicity,this method can be used in some domains such as photogrammetry,computer vision,etc.
A camera calibration method with co-line points is proposed,in which distortion center is located according to cross ratio invariability,and then distortion coefficients are calculated based on a line's central projection is a line.The emulation indicates that only if some measures are adopted to decrease the projection points' coordinate error,error of the distortion center would be less than 2 pixels and relative error of the distortion coefficients would be no more than 0.1.The experiment shows that these distortion parameters gained with the proposed method are good at a correcting distortion image.Because of its easiness and simplicity,this method can be used in some domains such as photogrammetry,computer vision,etc.
