Map
WeChat
Email alert
RSS2013 Vol. 37, No. 1
Display Method:
2013, 37(1): 1-5.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.001
[Abstract]
[PDF 889KB]
Abstract:
In order to achieve the dual}eam laser welding for T-joint,the dual-beam laser welding platform based on multiaxis computer numerical control machine tools and the seam tracking control based on vision sensors were adopted.Theoretical analysis and experiments were carried out,including the welding trajectory planning according to the established mathematic model of welding platform,the design of the position loop based on proportional,integral,derivative control and the algorithm of high speed tracking to improve the accuracy of the tracking system etc.Finally the proposed algorithm was verified in the welding experiments.The results show that the welding tracking control system can eliminate the deviation during laser weldingprocess with a high speed and a high precision by means of dynamic compensation,and can do the dual-beam laser welding for T-joint well.
In order to achieve the dual}eam laser welding for T-joint,the dual-beam laser welding platform based on multiaxis computer numerical control machine tools and the seam tracking control based on vision sensors were adopted.Theoretical analysis and experiments were carried out,including the welding trajectory planning according to the established mathematic model of welding platform,the design of the position loop based on proportional,integral,derivative control and the algorithm of high speed tracking to improve the accuracy of the tracking system etc.Finally the proposed algorithm was verified in the welding experiments.The results show that the welding tracking control system can eliminate the deviation during laser weldingprocess with a high speed and a high precision by means of dynamic compensation,and can do the dual-beam laser welding for T-joint well.
2013, 37(1): 6-10.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.002
Abstract:
In order to measure the thickness of thin plates accurately,the principle of thickness measurement based on double light path laser triangulation was summarized,and a gauging system based upon single lens laser triangulation was established.This system consists of two symmetrically-installed laser devices,a single lens imaging system an image acquisition system and a data analysis system.Then the principle of measurement measurement method and experimental facility were described.In the following part,the relation between system distinguishability and intersection angle among laser beam axis line and imaging lens axis was discussed,after that the least square fitting method was selected to get the fitted equation between measure thickness and flarespacing convenient to data analysis.Finally a calibration experiment was conducted to demonstrate the accuracy.It is found that this system not only eliminate the difficulty of synchronization problem laid in double light path laser triangulation method but also has a high distinguishability,it meets the commercial measurement demand well.
In order to measure the thickness of thin plates accurately,the principle of thickness measurement based on double light path laser triangulation was summarized,and a gauging system based upon single lens laser triangulation was established.This system consists of two symmetrically-installed laser devices,a single lens imaging system an image acquisition system and a data analysis system.Then the principle of measurement measurement method and experimental facility were described.In the following part,the relation between system distinguishability and intersection angle among laser beam axis line and imaging lens axis was discussed,after that the least square fitting method was selected to get the fitted equation between measure thickness and flarespacing convenient to data analysis.Finally a calibration experiment was conducted to demonstrate the accuracy.It is found that this system not only eliminate the difficulty of synchronization problem laid in double light path laser triangulation method but also has a high distinguishability,it meets the commercial measurement demand well.
2013, 37(1): 11-15.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.003
Abstract:
In order to obtain a working beam profile with high uniformity by microlens arrays pair in laser annealing equipment the elfect of relative position error of arrays pair was investigated.The dependence of the beam uniformity on the sixdegrees of freedom between two arrays was simulated with ray tracing method.It is found that the beam homogenization is most sensitive to roll angle error of the second array and precise control of relative position of two arrays is needed.The experimentresults indicate that with the aid of special lens mounts,the relative position of two arrays.an he controlled precisely and a flattop beam profile with beam uniformity of 0.039 is obtained as well.The laser annealing experiment for ultra shallow junction formation is demonstrated by this homogeneous beam successfully.
In order to obtain a working beam profile with high uniformity by microlens arrays pair in laser annealing equipment the elfect of relative position error of arrays pair was investigated.The dependence of the beam uniformity on the sixdegrees of freedom between two arrays was simulated with ray tracing method.It is found that the beam homogenization is most sensitive to roll angle error of the second array and precise control of relative position of two arrays is needed.The experimentresults indicate that with the aid of special lens mounts,the relative position of two arrays.an he controlled precisely and a flattop beam profile with beam uniformity of 0.039 is obtained as well.The laser annealing experiment for ultra shallow junction formation is demonstrated by this homogeneous beam successfully.
2013, 37(1): 16-19.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.004
Abstract:
For the high-speed optoelectronic systems applications,a new method of design an ultra-broadband optical detection module was introduced.It combines the traditional photoelectric with modern monolithic microwave integrated circuit technology.By collecting the cathode and anode photo currents of the PIN photodiode simultaneously,they were amplified by two amplifier circuits with different bandwidth range.Finally,the two different channel signals were combined by a consecutive pass-band diplexer.As a result,an ultra-broadband(direct-current~4GHz) and high responsivity(4900V/W) photoelectric detection module was obtained.This module solves the problem that any direct-current signal even low low-frequency optical signal can't be detected in a common high-speed optical detection module.
For the high-speed optoelectronic systems applications,a new method of design an ultra-broadband optical detection module was introduced.It combines the traditional photoelectric with modern monolithic microwave integrated circuit technology.By collecting the cathode and anode photo currents of the PIN photodiode simultaneously,they were amplified by two amplifier circuits with different bandwidth range.Finally,the two different channel signals were combined by a consecutive pass-band diplexer.As a result,an ultra-broadband(direct-current~4GHz) and high responsivity(4900V/W) photoelectric detection module was obtained.This module solves the problem that any direct-current signal even low low-frequency optical signal can't be detected in a common high-speed optical detection module.
2013, 37(1): 20-23.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.005
Abstract:
In order to measure the reflection spectra of fiber Bragg gratings at low cost,a simple measurement system was established based on white light interferometry.After processing the sampled interferogram,the reflection spectra was obtained with the spectral resolution about 3pm.Theoretical analysis of spectral resolution was conducted.Experiments show that the system has a fine spectral resolution.
In order to measure the reflection spectra of fiber Bragg gratings at low cost,a simple measurement system was established based on white light interferometry.After processing the sampled interferogram,the reflection spectra was obtained with the spectral resolution about 3pm.Theoretical analysis of spectral resolution was conducted.Experiments show that the system has a fine spectral resolution.
2013, 37(1): 24-27.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.006
Abstract:
A defect detection system for lines on indium tin oxide glass was designed and the detection precision reached 2m.Firstly,higher image magnification and image accuracy were obtained by using a high resolution linear CCD camera and the telephoto lenses;secondly,larger dynamic range was realized through the separation of camera and lens and a suitable modulation transfer function value was achieved through ceiling mounting the lens;the system precision and system stability were improved with a linear motor.At the same time,marble base was used to reduce the influence of surrounding vibration on the accuracy of the system.Finally,the advantages and disadvantages of system with different structure were concretely analyzed.Experiments show that the system has high precision,high stability,flexible operation,and other notable features.
A defect detection system for lines on indium tin oxide glass was designed and the detection precision reached 2m.Firstly,higher image magnification and image accuracy were obtained by using a high resolution linear CCD camera and the telephoto lenses;secondly,larger dynamic range was realized through the separation of camera and lens and a suitable modulation transfer function value was achieved through ceiling mounting the lens;the system precision and system stability were improved with a linear motor.At the same time,marble base was used to reduce the influence of surrounding vibration on the accuracy of the system.Finally,the advantages and disadvantages of system with different structure were concretely analyzed.Experiments show that the system has high precision,high stability,flexible operation,and other notable features.
2013, 37(1): 28-31.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.007
Abstract:
In order to find out the interference field of multi-beam surface plasma polaritons(SPPs),the theoretical interference model of multi-beam SPPs was deduced according to strict analytical expressions.The 2-D and 3-D lattice structure characteristics of SPPs interference were simulated and the resolution reached 1/6 wavelength.Its profile was the same as that of the ordinary laser beam interference field.It's very important for the multi-beam SPP lithography and manufacture of nano-scale optical devices.
In order to find out the interference field of multi-beam surface plasma polaritons(SPPs),the theoretical interference model of multi-beam SPPs was deduced according to strict analytical expressions.The 2-D and 3-D lattice structure characteristics of SPPs interference were simulated and the resolution reached 1/6 wavelength.Its profile was the same as that of the ordinary laser beam interference field.It's very important for the multi-beam SPP lithography and manufacture of nano-scale optical devices.
2013, 37(1): 32-35.
doi: 10.7510/jgjs.issn.1001-3806.2013.O1.008
Abstract:
In order to achieve the railway locomotive gauge measurement with high efficiency and high precision,a scanning laser-based gauge detector was designed.The cross-section scanning measurement was realized by fixing ranging sensors around the support frame.The field high-precision calibration method was focused.The system parameter was calibrated with the self-designed calibration card and the laser tracker.The system parameters,combined with the ranging sensor measurements,were used to calculate the 3-D coordinates of all the measured points in the rail coordinate system,and then the distance between the cross-sectional profile and the standard gauge was calculated so that the clearance was measured.Field experiments show that the system is in high efficiency and the system measurement accuracy of 0.5mm meets the need of bound detection.
In order to achieve the railway locomotive gauge measurement with high efficiency and high precision,a scanning laser-based gauge detector was designed.The cross-section scanning measurement was realized by fixing ranging sensors around the support frame.The field high-precision calibration method was focused.The system parameter was calibrated with the self-designed calibration card and the laser tracker.The system parameters,combined with the ranging sensor measurements,were used to calculate the 3-D coordinates of all the measured points in the rail coordinate system,and then the distance between the cross-sectional profile and the standard gauge was calculated so that the clearance was measured.Field experiments show that the system is in high efficiency and the system measurement accuracy of 0.5mm meets the need of bound detection.
2013, 37(1): 36-39.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.009
Abstract:
In order to improve the precision of peak-detection of a fiber Bragg grating demodulation system,it was studied based on the premature convergence characteristics of the genetic algorithm.It was expounded how the genetic algorithm can improve the accuracy of fiber Bragg grating demodulation.Taking a fiber Bragg grating demodulation system based on fiber Fabry-Perot(F-P)wavelength filter as example,the feasibility and reliability of the algorithm were testified.The peak reflected spectrum of the fiber Fabry-Perot filter fiber Bragg grating demodulation system was detected with MATLAB and its central wavelength was obtained.The effect of initial population number,genetic algebra,mutation rate on the peak detection of the algorithm was analyzed and a set of optimal parameters were obtained.The precision was equal or less than 3pm,standard deviation was less than 0.5pm for 50 repetition computations.The results show that the algorithm is stable,effective,and practical,can significantly reduce the noise of a fiber grating sensor system,improve the precision of demodulation.
In order to improve the precision of peak-detection of a fiber Bragg grating demodulation system,it was studied based on the premature convergence characteristics of the genetic algorithm.It was expounded how the genetic algorithm can improve the accuracy of fiber Bragg grating demodulation.Taking a fiber Bragg grating demodulation system based on fiber Fabry-Perot(F-P)wavelength filter as example,the feasibility and reliability of the algorithm were testified.The peak reflected spectrum of the fiber Fabry-Perot filter fiber Bragg grating demodulation system was detected with MATLAB and its central wavelength was obtained.The effect of initial population number,genetic algebra,mutation rate on the peak detection of the algorithm was analyzed and a set of optimal parameters were obtained.The precision was equal or less than 3pm,standard deviation was less than 0.5pm for 50 repetition computations.The results show that the algorithm is stable,effective,and practical,can significantly reduce the noise of a fiber grating sensor system,improve the precision of demodulation.
2013, 37(1): 40-43.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.010
Abstract:
In order to improve the computational efficiency of computer generated hologram(CGH),a novel algorithm was proposed to obtain multiple-type reconstruction images of CGH based on spectrum diffraction theory.The reconstruction images can be rotated,sheared and inversed by just transforming the coordinates of the Fourier spectrum so that the calculation amount is reduced a lot.Besides,it was also validated in experiments.The experiment results prove the new algorithm is feasible.
In order to improve the computational efficiency of computer generated hologram(CGH),a novel algorithm was proposed to obtain multiple-type reconstruction images of CGH based on spectrum diffraction theory.The reconstruction images can be rotated,sheared and inversed by just transforming the coordinates of the Fourier spectrum so that the calculation amount is reduced a lot.Besides,it was also validated in experiments.The experiment results prove the new algorithm is feasible.
2013, 37(1): 44-47.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.011
Abstract:
In order to find the phase information,the noise,the shadow,fringe break,under-sampling and other adverse factors must be overcome.When processing the under-sampling problem,the radial shearing method was introduced into phaseunwrapping process,in which a phase image for unwrapping was obtained by shearing a wrapped phase reconstructed by a wrapped phase built numerically after zooming the original one for several times so that the difficult problem becomes multiple simpler problems.The simulation and experimental results prove that the proposed algorithm can deal with the wrapped phase of serious under-samplings.Compared with the traditional unwrapping algorithms,this algorithm has a wider application.
In order to find the phase information,the noise,the shadow,fringe break,under-sampling and other adverse factors must be overcome.When processing the under-sampling problem,the radial shearing method was introduced into phaseunwrapping process,in which a phase image for unwrapping was obtained by shearing a wrapped phase reconstructed by a wrapped phase built numerically after zooming the original one for several times so that the difficult problem becomes multiple simpler problems.The simulation and experimental results prove that the proposed algorithm can deal with the wrapped phase of serious under-samplings.Compared with the traditional unwrapping algorithms,this algorithm has a wider application.
2013, 37(1): 48-51.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.012
Abstract:
In order to optimize the synchronization algorithm under the low signal-to-noise ratio(SNR) environment in a global system for mobile communication(GSM)system,the improved Gaussian-filtered minimum shift keying(GMSK) modulation signal synchronization algorithm was adopted to obtain the comparison chart of signal synchronization success rate.At the receiving end the phase of GMSK was reversed first,symbolized,and be processed by synchronization algorithm with slide-relative synchronous progress.The results show that the synchronization algorithm has a higher success rate than the traditional algorithm based on the sliding of the training sequence,which can not only improve the synchronization success rate significantly in the low SNR,but also simplify the threshold calculation process.This result means a great significance to the signal modulation in the low SNR environment.
In order to optimize the synchronization algorithm under the low signal-to-noise ratio(SNR) environment in a global system for mobile communication(GSM)system,the improved Gaussian-filtered minimum shift keying(GMSK) modulation signal synchronization algorithm was adopted to obtain the comparison chart of signal synchronization success rate.At the receiving end the phase of GMSK was reversed first,symbolized,and be processed by synchronization algorithm with slide-relative synchronous progress.The results show that the synchronization algorithm has a higher success rate than the traditional algorithm based on the sliding of the training sequence,which can not only improve the synchronization success rate significantly in the low SNR,but also simplify the threshold calculation process.This result means a great significance to the signal modulation in the low SNR environment.
2013, 37(1): 52-55.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.013
Abstract:
Short-time Fourier transformation is widely used to expand 1-D signal in temporal domain or spectral domain into the corresponding 2-D case in time-frequency domain.Effect of dispersion and initial chirp of pulse in fiber on signal propagation was numerically analyzed in detail by employing short-time Fourier transformation.Compared with conventional Fourier transformation,short-time Fourier transformation can more directly describe how the temporal and spectral features of optical pulse evolution vary with both dispersion and initial chirp.In addition,the evolutions of new frequency chirp induced by both dispersion and initial chirp can be clearly seen by using time-frequency analysis resulting from short-time Fourier transformation.Therefore,it completely overcomes the disadvantage of conventional Fourier transformation that is used to only compare signal transient in the spectral or temporal domain separately,and short-time Fourier transformation is expected to provide a new and effective approach to analyze the pulse propagation in fiber.
Short-time Fourier transformation is widely used to expand 1-D signal in temporal domain or spectral domain into the corresponding 2-D case in time-frequency domain.Effect of dispersion and initial chirp of pulse in fiber on signal propagation was numerically analyzed in detail by employing short-time Fourier transformation.Compared with conventional Fourier transformation,short-time Fourier transformation can more directly describe how the temporal and spectral features of optical pulse evolution vary with both dispersion and initial chirp.In addition,the evolutions of new frequency chirp induced by both dispersion and initial chirp can be clearly seen by using time-frequency analysis resulting from short-time Fourier transformation.Therefore,it completely overcomes the disadvantage of conventional Fourier transformation that is used to only compare signal transient in the spectral or temporal domain separately,and short-time Fourier transformation is expected to provide a new and effective approach to analyze the pulse propagation in fiber.
2013, 37(1): 56-58.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.014
Abstract:
In order to monitor and control laser derusting process in real time,the light intensity of plasma was detected with a photodiode,and the light signal was transformed into voltage signal with an oscilloscope,so that the curves of peak voltage versus laser energy and laser impact number were obtained.The results show that the derusting threshold and whether the metal surface is cleaned clearly can be determined according to the tendency change of the peak voltage signal.
In order to monitor and control laser derusting process in real time,the light intensity of plasma was detected with a photodiode,and the light signal was transformed into voltage signal with an oscilloscope,so that the curves of peak voltage versus laser energy and laser impact number were obtained.The results show that the derusting threshold and whether the metal surface is cleaned clearly can be determined according to the tendency change of the peak voltage signal.
2013, 37(1): 59-62.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.015
Abstract:
In order to analyze the nonreciprocal effect induced by longitudinal magnetic field in a ring laser,a mathematic model for the opposite waves in the ring laser was made based on Jones matrix.The ellipticity,azimuth and frequency difference of the opposite waves in case of slightly noncoplanar resonator were calculated.It is found that:the gain of the active medium subjected to a longitudinal magnetic field can influence the ellipticity and azimuth of the opposite waves;the magnetic sensitivity increases with the gain of the active medium and it is influenced by the detuning of the ring laser.The results obtained are helpful to reduce the magnetic sensitivity in a ring laser.
In order to analyze the nonreciprocal effect induced by longitudinal magnetic field in a ring laser,a mathematic model for the opposite waves in the ring laser was made based on Jones matrix.The ellipticity,azimuth and frequency difference of the opposite waves in case of slightly noncoplanar resonator were calculated.It is found that:the gain of the active medium subjected to a longitudinal magnetic field can influence the ellipticity and azimuth of the opposite waves;the magnetic sensitivity increases with the gain of the active medium and it is influenced by the detuning of the ring laser.The results obtained are helpful to reduce the magnetic sensitivity in a ring laser.
2013, 37(1): 63-67.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.016
Abstract:
In order to generate 2m laser,a novel method was adopted with periodically poled lithium niobate(PPLN) as a nonlinear crystal in optical parametric oscillator(OPO).From the Sellmeier function of PPLN,given the momentum conservation and energy conservation,series of theoretical analysis and numerical calculation are conducted.Firstly,it was obtained that the polarization period of PPLN was 31.35m at 120℃ Then the curves of the relations between the wavelength and polarization period,between the wavelength and the incident angle were drawn.Finally,starting from the phase synchronization factor sinc2(Kl/2),the allowance angle,allowance polarization period and allowance temperature were calculated.This method not only can overcome walk-off effect of birefringence and dispersion,but also make full use of the maximum effective nonlinear coefficient of the crystals,so the efficiency of the conversion can be increased.These theoretical results provide the foundation for the future experimental study about PPLN-quasi-phase matching-OPOs.
In order to generate 2m laser,a novel method was adopted with periodically poled lithium niobate(PPLN) as a nonlinear crystal in optical parametric oscillator(OPO).From the Sellmeier function of PPLN,given the momentum conservation and energy conservation,series of theoretical analysis and numerical calculation are conducted.Firstly,it was obtained that the polarization period of PPLN was 31.35m at 120℃ Then the curves of the relations between the wavelength and polarization period,between the wavelength and the incident angle were drawn.Finally,starting from the phase synchronization factor sinc2(Kl/2),the allowance angle,allowance polarization period and allowance temperature were calculated.This method not only can overcome walk-off effect of birefringence and dispersion,but also make full use of the maximum effective nonlinear coefficient of the crystals,so the efficiency of the conversion can be increased.These theoretical results provide the foundation for the future experimental study about PPLN-quasi-phase matching-OPOs.
2013, 37(1): 72-76.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.018
Abstract:
Laser producing 3-D microstructures inside KDP crystals is an effective way to suppress the transverse stimulated Raman scattering(TSRS) effect in high power lasers.The transmission characteristics of focused laser inside KDP crystal was simulated to investigate the feasibility of laser making 3-D microstructures and the effects of laser parameters on the machining accuracy,efficiency and success rates.The effects of the focus peak power density,spot distortion and the migration are the main factors affecting the machining accuracy and causing crystal fragmentation.The size and shape of the e-polarization focus will distort and its peak power density decreases rapidly with the increasing of angle between incident laser and crystal optical axis.The results show that the effect of the e-polarization laser will increase the processing efficiency more than twice when the angle is less than 15 and can be neglected in the low-energy or cause crystal fragmentation easily in high-energy when the angle is greater than 30.
Laser producing 3-D microstructures inside KDP crystals is an effective way to suppress the transverse stimulated Raman scattering(TSRS) effect in high power lasers.The transmission characteristics of focused laser inside KDP crystal was simulated to investigate the feasibility of laser making 3-D microstructures and the effects of laser parameters on the machining accuracy,efficiency and success rates.The effects of the focus peak power density,spot distortion and the migration are the main factors affecting the machining accuracy and causing crystal fragmentation.The size and shape of the e-polarization focus will distort and its peak power density decreases rapidly with the increasing of angle between incident laser and crystal optical axis.The results show that the effect of the e-polarization laser will increase the processing efficiency more than twice when the angle is less than 15 and can be neglected in the low-energy or cause crystal fragmentation easily in high-energy when the angle is greater than 30.
2013, 37(1): 77-81.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.019
Abstract:
In order to overcome shortcomings,such as blind spots and high expense,in space coordinate measurement with a total station and laser tracker,a space coordinate measurement method was put forward based on theodolites and rangefinders.The distance of a few target dots along the laser beam were measured with a laser rangefinder,at the same time these target dots were observed with a theodolite so that the horizontal angle and zenith angle of each target point were obtained.In the following data processing,the public plane,determined by the rays consisting of each target point and the origin of the theodolite,was calculated with the least square method,then these rays were projected to the public plane to obtain the corresponding projection rays,and the coordinates of each target dot were calculated based on these projection rays and the distances between target dots.Finally,the expression of the space line indicating the laser beam was fitted.Known the equation of the space line,the coordinates of to-be-tested dots in the theodolite coordinate system can be calculated if only measuring the distance between the dot and laser rangefinder.This measurement gives access to multi-point dynamic non-contact space coordinate measurement,which is difficult for a total station and laser tracker to achieve.
In order to overcome shortcomings,such as blind spots and high expense,in space coordinate measurement with a total station and laser tracker,a space coordinate measurement method was put forward based on theodolites and rangefinders.The distance of a few target dots along the laser beam were measured with a laser rangefinder,at the same time these target dots were observed with a theodolite so that the horizontal angle and zenith angle of each target point were obtained.In the following data processing,the public plane,determined by the rays consisting of each target point and the origin of the theodolite,was calculated with the least square method,then these rays were projected to the public plane to obtain the corresponding projection rays,and the coordinates of each target dot were calculated based on these projection rays and the distances between target dots.Finally,the expression of the space line indicating the laser beam was fitted.Known the equation of the space line,the coordinates of to-be-tested dots in the theodolite coordinate system can be calculated if only measuring the distance between the dot and laser rangefinder.This measurement gives access to multi-point dynamic non-contact space coordinate measurement,which is difficult for a total station and laser tracker to achieve.
2013, 37(1): 82-84.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.020
Abstract:
In order to control the polarization states and increase the extinction ratio of the TE and TM output beam,a novel tunable polarization controller was proposed and demonstrated by introducing birefringent material into the coupling prism and polymer acted as the guiding layer of symmetrical metal cladding waveguide(SMCW).In this structure,the guide mode resonance can not simultaneously be excited by TE and TM polarizations at the same incident angle.The incident laser beam energy of the polarization which excites guide mode resonance is coupled into the SMCW,while that of the polarization which dose not excite guide mode resonance is almost reflected.As a result,the TE and TM polarization beams can be separated.Moreover,the polarization selector can be tuned assisted by changing the resonance condition of the guiding mode via applying direct-current voltage on the guiding-layer.The research indicates the inset loss is smaller than 0.2dB and the driving voltage is up to 19V and the extinction ratio is larger than 27dB due to the twice attenuation totally reflected technique.This method is valuable in many potential applications,such as optical information processing,optical routing,optical switch and image processing.
In order to control the polarization states and increase the extinction ratio of the TE and TM output beam,a novel tunable polarization controller was proposed and demonstrated by introducing birefringent material into the coupling prism and polymer acted as the guiding layer of symmetrical metal cladding waveguide(SMCW).In this structure,the guide mode resonance can not simultaneously be excited by TE and TM polarizations at the same incident angle.The incident laser beam energy of the polarization which excites guide mode resonance is coupled into the SMCW,while that of the polarization which dose not excite guide mode resonance is almost reflected.As a result,the TE and TM polarization beams can be separated.Moreover,the polarization selector can be tuned assisted by changing the resonance condition of the guiding mode via applying direct-current voltage on the guiding-layer.The research indicates the inset loss is smaller than 0.2dB and the driving voltage is up to 19V and the extinction ratio is larger than 27dB due to the twice attenuation totally reflected technique.This method is valuable in many potential applications,such as optical information processing,optical routing,optical switch and image processing.
2013, 37(1): 85-88.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.021
Abstract:
Single-frequency all-solid-state infrared lasers are very important for commercial and military applications.Their typical principle and the technical approaches were summarized.Their development status at wavelengths of 1.064m,1.5m~1.6m and 2m was reviewed.The characteristics of the main schemes were compared.Finally,the new development in the future was predicated.
Single-frequency all-solid-state infrared lasers are very important for commercial and military applications.Their typical principle and the technical approaches were summarized.Their development status at wavelengths of 1.064m,1.5m~1.6m and 2m was reviewed.The characteristics of the main schemes were compared.Finally,the new development in the future was predicated.
2013, 37(1): 89-92.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.022
Abstract:
In order to study effect of foam on laser transmission quantitatively,based on the absorption,reflection and scattering characteristics of electromagnetic wave,attenuation blanking mechanism of foam was analyzed.According to different foam condition,foam was divided into discrete foam and adhesive foam,and their transmission and energy attenuation were calculated quantitatively with Lamber-Beer law and theories of geometrical optics and electromagnetic wave propagation.The numerical simulation results based on MATLAB tool show that foam has obvious effect on laser attenuation,with increasing of foam thickness the transmission of laser is diminishing,and it is similar to experimental.The rationality of the model is proved further.
In order to study effect of foam on laser transmission quantitatively,based on the absorption,reflection and scattering characteristics of electromagnetic wave,attenuation blanking mechanism of foam was analyzed.According to different foam condition,foam was divided into discrete foam and adhesive foam,and their transmission and energy attenuation were calculated quantitatively with Lamber-Beer law and theories of geometrical optics and electromagnetic wave propagation.The numerical simulation results based on MATLAB tool show that foam has obvious effect on laser attenuation,with increasing of foam thickness the transmission of laser is diminishing,and it is similar to experimental.The rationality of the model is proved further.
2013, 37(1): 93-96.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.023
Abstract:
In order to minimize the measurement errors,an improved iterative Boltzmann plot method and Lorentz fitting method were used.The electron temperature Te in brass plasma was 6051K with the iterative calculation,and the electron density Ne of 3.31017cm-3 was inferred from the Stark broadened profile of Cu Ⅰ 324.75mm.The results show that the correlation coefficient is increased from 0.73 to 0.98 after 9 iterations in calculation of Te,and the correlation coefficient increases from 0.90 to 0.96 after 15 averaged numbers in calculation of Ne.The results are helpful to accurately calculate the parameters of plasma.
In order to minimize the measurement errors,an improved iterative Boltzmann plot method and Lorentz fitting method were used.The electron temperature Te in brass plasma was 6051K with the iterative calculation,and the electron density Ne of 3.31017cm-3 was inferred from the Stark broadened profile of Cu Ⅰ 324.75mm.The results show that the correlation coefficient is increased from 0.73 to 0.98 after 9 iterations in calculation of Te,and the correlation coefficient increases from 0.90 to 0.96 after 15 averaged numbers in calculation of Ne.The results are helpful to accurately calculate the parameters of plasma.
2013, 37(1): 97-100.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.024
Abstract:
In order to satisfy the exciting technique of a master oscillator power amplifier(MOPA) excimer laser for industrial use,a high-repetition and high-accuracy pulse charge power was designed.The power can simultaneously charge the charging capacitors for the dual chamber excimer laser with a LC resonant circuit with a voltage ratio of 1.87.By regulating the work schedule,the power can discharge at kHz level frequency.When the output voltage was about 1300V,the voltage precision was0.18%.The charging voltage can be controlled at high accuracy by the voltage feedback regulation.
In order to satisfy the exciting technique of a master oscillator power amplifier(MOPA) excimer laser for industrial use,a high-repetition and high-accuracy pulse charge power was designed.The power can simultaneously charge the charging capacitors for the dual chamber excimer laser with a LC resonant circuit with a voltage ratio of 1.87.By regulating the work schedule,the power can discharge at kHz level frequency.When the output voltage was about 1300V,the voltage precision was0.18%.The charging voltage can be controlled at high accuracy by the voltage feedback regulation.
2013, 37(1): 101-104.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.025
Abstract:
In order to measure refractive index of liquid with high-precision and low-cost,a liquid refractive index sensor based on a micro-hole in the single-mode fiber was fabricated by means of water-assisted femtosecond laser ablation method.The responses of transmission loss of the sensor to the refractive index and micro-hole length were investigated.Based on the ray theory,the sensing mechanism was analyzed.The effect of temperature disturbance on the sensor performance was also discussed.The experiment results show that the sensor has a good linear response in the refractive index range of 1.333~1.413,the sensitivity of the sensor can achieve 157.48dB/RIU and it is less susceptible to temperature change.Compared with other fiber refractive index sensors,optical fiber micro-hole sensors have the outstanding advantages,including compact,easy to fabricate,high sensitivity insensitive to temperature and low cost,etc.Therefore optical fiber micro-hole sensors can have extensive application in the fields of biochemical measurement.
In order to measure refractive index of liquid with high-precision and low-cost,a liquid refractive index sensor based on a micro-hole in the single-mode fiber was fabricated by means of water-assisted femtosecond laser ablation method.The responses of transmission loss of the sensor to the refractive index and micro-hole length were investigated.Based on the ray theory,the sensing mechanism was analyzed.The effect of temperature disturbance on the sensor performance was also discussed.The experiment results show that the sensor has a good linear response in the refractive index range of 1.333~1.413,the sensitivity of the sensor can achieve 157.48dB/RIU and it is less susceptible to temperature change.Compared with other fiber refractive index sensors,optical fiber micro-hole sensors have the outstanding advantages,including compact,easy to fabricate,high sensitivity insensitive to temperature and low cost,etc.Therefore optical fiber micro-hole sensors can have extensive application in the fields of biochemical measurement.
Analysis of the cavity ring-down signal based on self-consistent equations and the transfer function
2013, 37(1): 105-108.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.026
Abstract:
In order to better understand the physical nature and measurement process of the cavity ring-down technique and analyze the signal,the self-consistent equations and the Q concept of a passive optical cavity were used to deduce the basic principle.The transfer function was introduced to analyze the essential features of different signals under different conditions.Results show that this analytical method is reliable and can provide theoretical guide for cavity ring-down measurements in different areas such as the calibration of ultra-low loss films and the measurement of the intra-cavity absorption spectrum.
In order to better understand the physical nature and measurement process of the cavity ring-down technique and analyze the signal,the self-consistent equations and the Q concept of a passive optical cavity were used to deduce the basic principle.The transfer function was introduced to analyze the essential features of different signals under different conditions.Results show that this analytical method is reliable and can provide theoretical guide for cavity ring-down measurements in different areas such as the calibration of ultra-low loss films and the measurement of the intra-cavity absorption spectrum.
2013, 37(1): 109-113.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.027
Abstract:
In order to study the fluorescent spectral characteristics of edible oil after heating,at different heating time and number of heating times,the fluorescent spectra of 7 kinds of edible oil were detected with an American Roper Scientific SP-2558 multi-functional spectral measuring system.At the same time,the mechanism of the fluorescent spectra was analyzed.The characteristic data of the fluorescent spectra of heated oil was observed.The results show that the number of the edible oil's fluorescent peaks decrease,the peak wavelengths move towards the longer wave region and the fluorescent intensity increases with the increase of heating time or times.The changing extent of soybean oil's fluorescent spectral characteristics is the minimum among these kinds of edible oil.These results provide reference for quality test and safety for edible oil.
In order to study the fluorescent spectral characteristics of edible oil after heating,at different heating time and number of heating times,the fluorescent spectra of 7 kinds of edible oil were detected with an American Roper Scientific SP-2558 multi-functional spectral measuring system.At the same time,the mechanism of the fluorescent spectra was analyzed.The characteristic data of the fluorescent spectra of heated oil was observed.The results show that the number of the edible oil's fluorescent peaks decrease,the peak wavelengths move towards the longer wave region and the fluorescent intensity increases with the increase of heating time or times.The changing extent of soybean oil's fluorescent spectral characteristics is the minimum among these kinds of edible oil.These results provide reference for quality test and safety for edible oil.
2013, 37(1): 114-117.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.028
Abstract:
In order to analyze diffraction field of orthogonal cosine-gratings,it was analyzed based on the method of wave-front phase factors and considering the influence of limited aperture of grating.The phase-front function,amplitude and intensity expressions of the diffraction field were deduced.The amplitude and intensity of light distribution diagram of phase plane were obtained.Finally,the half-angle-width of maximum value in the center was given.This study may further provide a theoretical foundation to analyze diffraction of orthogonal cosine-gratings.
In order to analyze diffraction field of orthogonal cosine-gratings,it was analyzed based on the method of wave-front phase factors and considering the influence of limited aperture of grating.The phase-front function,amplitude and intensity expressions of the diffraction field were deduced.The amplitude and intensity of light distribution diagram of phase plane were obtained.Finally,the half-angle-width of maximum value in the center was given.This study may further provide a theoretical foundation to analyze diffraction of orthogonal cosine-gratings.
2013, 37(1): 118-120.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.029
Abstract:
A improved Horn-Schunck algorithm method was proposed to judge nuclear explosion.The optic flow field of a consecutive sequence of frames of nuclear explosion was calculated and the picture of optic flow field was drawn.For example,the average horizontal optical flow field was 0.018181pixel/s with a mean square deviation(MSD)of 0.375775pixel/s and the average vertical optical flow field was -0.503308pixel/s with a MSD of 0.896142pixel/s at the 1159th frame and the 1160th frame.A preliminary judgment can be made that it is a nuclear explosion according the picture and velocities distribution.
A improved Horn-Schunck algorithm method was proposed to judge nuclear explosion.The optic flow field of a consecutive sequence of frames of nuclear explosion was calculated and the picture of optic flow field was drawn.For example,the average horizontal optical flow field was 0.018181pixel/s with a mean square deviation(MSD)of 0.375775pixel/s and the average vertical optical flow field was -0.503308pixel/s with a MSD of 0.896142pixel/s at the 1159th frame and the 1160th frame.A preliminary judgment can be made that it is a nuclear explosion according the picture and velocities distribution.
2013, 37(1): 121-125.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.030
Abstract:
CaTiO3 biocoating was in-situ fabricated on Ti-6Al-4V substrate via laser cladding technology to improve the bioactivity of titanium alloy.A pulsed YAG laser with a power of 500W was introduced as the radiation source.A mixture of pure titanium powder(average particle size 20m) and CaCO3 powder with a certain weight ratio was preplaced on the substrate as the precursor.The mechanism of in-situ fabrication of CaTiO3 biocoating was investigated by thermodynamic analysis.The effects of laser technologies such as laser scan speed and electrical current on the phase constituents and the surface morphology of the samples were studied.X-ray diffraction characterization and laser confocal scanning microscopy investigation showed that the proper parameters for laser cladding were as the following:pulsed frequency 30Hz,pulse width 1.0ms,defocus distance 15mm,laser scanning speed about 3mm/s,and electrical currency 240A.CaTiO3 and part of titanium oxides are the main phases in the coating.Optical microscopy result revealed that the microstructure in the coating was characterized as fine dendrites and cellular structure.A metallurgical bonding between the coating and the substrate was obtained.
CaTiO3 biocoating was in-situ fabricated on Ti-6Al-4V substrate via laser cladding technology to improve the bioactivity of titanium alloy.A pulsed YAG laser with a power of 500W was introduced as the radiation source.A mixture of pure titanium powder(average particle size 20m) and CaCO3 powder with a certain weight ratio was preplaced on the substrate as the precursor.The mechanism of in-situ fabrication of CaTiO3 biocoating was investigated by thermodynamic analysis.The effects of laser technologies such as laser scan speed and electrical current on the phase constituents and the surface morphology of the samples were studied.X-ray diffraction characterization and laser confocal scanning microscopy investigation showed that the proper parameters for laser cladding were as the following:pulsed frequency 30Hz,pulse width 1.0ms,defocus distance 15mm,laser scanning speed about 3mm/s,and electrical currency 240A.CaTiO3 and part of titanium oxides are the main phases in the coating.Optical microscopy result revealed that the microstructure in the coating was characterized as fine dendrites and cellular structure.A metallurgical bonding between the coating and the substrate was obtained.
2013, 37(1): 126-129.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.031
Abstract:
In order to study the propagation characteristics of sinh-Gaussian beams in gradient-index medium,the analytical expression of the intensity was derived based on the general Huygens-Fresnel diffraction integral.Based on the second-order moment definition,the analytical expression for the beam width and the waist location were deduced.The intensity,facular size,beam waist and its position were calculated.The results show that the axial intensity changes periodically and the transverse intensity distribution are largely affected by the nonlinearity of the medium and the modulation parameter of the beams.The spot site and waist location can be changed by adjusting the parameter appropriately.
In order to study the propagation characteristics of sinh-Gaussian beams in gradient-index medium,the analytical expression of the intensity was derived based on the general Huygens-Fresnel diffraction integral.Based on the second-order moment definition,the analytical expression for the beam width and the waist location were deduced.The intensity,facular size,beam waist and its position were calculated.The results show that the axial intensity changes periodically and the transverse intensity distribution are largely affected by the nonlinearity of the medium and the modulation parameter of the beams.The spot site and waist location can be changed by adjusting the parameter appropriately.
2013, 37(1): 130-133.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.032
Abstract:
In order to study the kinetic energy of the accelerated positron in the laser-driven wakefield induced from the interaction of sine laser pulse and the low density plasma,the kinetic energy of positron in the wakefield driven by the symmetric and asymmetric sine laser pulses was numerically simulated.Numerical results show that the number of the accelerated positrons in the wakefield and their initial speed are increased due to the effect of Raman scattering.Moreover,since the rising part of the asymmetric sine pulse is steeper than the symmetric sine pulse,the positrons obtain a higher pondermotive potential and the asymmetric sine pulse induces a high intensity wakefield.As a result,the kinetic energy of the positrons driven by the asymmetric sine laser pulse is higher than that driven by the symmetric sine laser pulse.These results indicate that the asymmetric sine laser pulse can effectively improve the acceleration efficiency of the positrons.
In order to study the kinetic energy of the accelerated positron in the laser-driven wakefield induced from the interaction of sine laser pulse and the low density plasma,the kinetic energy of positron in the wakefield driven by the symmetric and asymmetric sine laser pulses was numerically simulated.Numerical results show that the number of the accelerated positrons in the wakefield and their initial speed are increased due to the effect of Raman scattering.Moreover,since the rising part of the asymmetric sine pulse is steeper than the symmetric sine pulse,the positrons obtain a higher pondermotive potential and the asymmetric sine pulse induces a high intensity wakefield.As a result,the kinetic energy of the positrons driven by the asymmetric sine laser pulse is higher than that driven by the symmetric sine laser pulse.These results indicate that the asymmetric sine laser pulse can effectively improve the acceleration efficiency of the positrons.
2013, 37(1): 134-138.
doi: 10.7510/jgjs.issn.1001-3806.2013.01.033
Abstract:
In order to understand the generation mechanism of self-generated magnetic field and electron thermal conduction characteristics in the process of the interaction between ultra-intense laser and plasma,the strength and spatial distribution of the self-generated magnetic field under different laser power density were estimated by means of electromagnetic relativistic particle-in cell program simulation.The electron-thermal evolvement phenomenon was observed as described by the Spitzer-Harm theory.It is shown that different from previous models,the initial non-Maxwell distributed plasma stimulates the electromagnetic instability in the plasma because of the random thermal motion of electrons.It is not the strong magnetic field excited by instability makes the electron beam deposit the energy within very short distance.Meanwhile,it restrains the electron thermo current to be formed when the laser ponderomotive force bursts through the electron.This result is helpful to the self-magnetic field generation and electron thermal conduction in fast ignition of inertial confinement fusion.
In order to understand the generation mechanism of self-generated magnetic field and electron thermal conduction characteristics in the process of the interaction between ultra-intense laser and plasma,the strength and spatial distribution of the self-generated magnetic field under different laser power density were estimated by means of electromagnetic relativistic particle-in cell program simulation.The electron-thermal evolvement phenomenon was observed as described by the Spitzer-Harm theory.It is shown that different from previous models,the initial non-Maxwell distributed plasma stimulates the electromagnetic instability in the plasma because of the random thermal motion of electrons.It is not the strong magnetic field excited by instability makes the electron beam deposit the energy within very short distance.Meanwhile,it restrains the electron thermo current to be formed when the laser ponderomotive force bursts through the electron.This result is helpful to the self-magnetic field generation and electron thermal conduction in fast ignition of inertial confinement fusion.
