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RSS2006 Vol. 30, No. 6
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2006, 30(6): 561-563,580.
[Abstract]
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Abstract:
Based on Mie theory,the phase difference model for calculating and analyzing the spatial distribution of scattering intensity from a spherical particle on a smooth surface radiated by a linearly polarized light beam is obtained.The differential scattering cross section is calculated when the s and p polarized light irritates the particles at 0° and 70° respectively.The calculation results are compared with experimental results.
Based on Mie theory,the phase difference model for calculating and analyzing the spatial distribution of scattering intensity from a spherical particle on a smooth surface radiated by a linearly polarized light beam is obtained.The differential scattering cross section is calculated when the s and p polarized light irritates the particles at 0° and 70° respectively.The calculation results are compared with experimental results.
2006, 30(6): 564-566,569.
Abstract:
In order to improve the frequency stabilization of the Doppler modulator,a series of affecting factors are considered in depth and optimized in the aspects of optics,mechanics and electronics.The experiment results show that:the frequency stabilization of the optimized Doppler modulator has already reached RMS error about ±1%,which could meet the need of reference signal of the lock-in amplifier.
In order to improve the frequency stabilization of the Doppler modulator,a series of affecting factors are considered in depth and optimized in the aspects of optics,mechanics and electronics.The experiment results show that:the frequency stabilization of the optimized Doppler modulator has already reached RMS error about ±1%,which could meet the need of reference signal of the lock-in amplifier.
2006, 30(6): 567-569.
Abstract:
To investigate the technique of laser etching silicon under different mediums,micromachining of silicon was conducted using a short-pulse(FWHM is 20ns) KrF excimer laserwith energy of 150mJ~250mJ.Laser etching were tested on a silicon workpiece both in air and under water.Based on the results of experiments,basic etching appearance and etching velocities by excimer laser etching silicon under the two mediums were studied,and then the differences were compared.As a result,the molten material is easy to be removed in water-assisted micromachining of silicon,which helps to improve the processed surface quality;and the restriction of water improves the impact effect which increases the etching velocity.
To investigate the technique of laser etching silicon under different mediums,micromachining of silicon was conducted using a short-pulse(FWHM is 20ns) KrF excimer laserwith energy of 150mJ~250mJ.Laser etching were tested on a silicon workpiece both in air and under water.Based on the results of experiments,basic etching appearance and etching velocities by excimer laser etching silicon under the two mediums were studied,and then the differences were compared.As a result,the molten material is easy to be removed in water-assisted micromachining of silicon,which helps to improve the processed surface quality;and the restriction of water improves the impact effect which increases the etching velocity.
2006, 30(6): 570-573,577.
Abstract:
For the different surface treatment of the laser crystal,a mathematical model was created to describe the absorbed energy distribution in the laser crystal of the multi LD arrays circle-side-pumped solid-state lasers.Ray-tracing method was taken to calculate the distribution in the crystal.The study was mainly about the influence of the different surface treatment of the laser crystal on the distribution of the absorbed energy,and the surface treatment can restrain the amplified spontaneous emission(ASE) in the resonator but decrease the laser efficiency.The result indicates that increasing the scatter ratio of the crystal surface can restrain the ASE but reduce the laser efficiency.
For the different surface treatment of the laser crystal,a mathematical model was created to describe the absorbed energy distribution in the laser crystal of the multi LD arrays circle-side-pumped solid-state lasers.Ray-tracing method was taken to calculate the distribution in the crystal.The study was mainly about the influence of the different surface treatment of the laser crystal on the distribution of the absorbed energy,and the surface treatment can restrain the amplified spontaneous emission(ASE) in the resonator but decrease the laser efficiency.The result indicates that increasing the scatter ratio of the crystal surface can restrain the ASE but reduce the laser efficiency.
2006, 30(6): 574-577.
Abstract:
The small dipole aperture antenna provides a normal way for THz radiation,for which the Drude-Lorentz theory provides method to calculate the terahertz waves from photoconductor.For sake of this Drude-Lorentz theory is not suitable for large-aperture photoconductive antenna,the calculation of terahertz radiation from biased photoconductive antenna(Drude-Lorentz theory) is reported,and a meliorated calculation method of carriers' density is put forward.Based on the new calculation model and simulation results,the effect of different factors on THz radiation is analyzed.The results show that the new calculation model is more suitable for a large aperture antenna.
The small dipole aperture antenna provides a normal way for THz radiation,for which the Drude-Lorentz theory provides method to calculate the terahertz waves from photoconductor.For sake of this Drude-Lorentz theory is not suitable for large-aperture photoconductive antenna,the calculation of terahertz radiation from biased photoconductive antenna(Drude-Lorentz theory) is reported,and a meliorated calculation method of carriers' density is put forward.Based on the new calculation model and simulation results,the effect of different factors on THz radiation is analyzed.The results show that the new calculation model is more suitable for a large aperture antenna.
2006, 30(6): 578-580.
Abstract:
Zn,Mg:LiNbO3 crystal was grown by the pulling method from the melt and its composition,growth,optical homogeneity,photo-refraction resistance and frequency doubling were investigated.The grown crystal was 40mm in diameter and 70mm in length,the birefringence gradient of Zn,Mg:LiNbO3 crystal was less than 10-4/cm,the frequency doubling output pulse energy was 20mJ at 0.532μm and the conversation efficiency was 45%.This crystal was a new promising nonlinear optical material.
Zn,Mg:LiNbO3 crystal was grown by the pulling method from the melt and its composition,growth,optical homogeneity,photo-refraction resistance and frequency doubling were investigated.The grown crystal was 40mm in diameter and 70mm in length,the birefringence gradient of Zn,Mg:LiNbO3 crystal was less than 10-4/cm,the frequency doubling output pulse energy was 20mJ at 0.532μm and the conversation efficiency was 45%.This crystal was a new promising nonlinear optical material.
2006, 30(6): 581-584,588.
Abstract:
Some recent work on weak-light nonlinear optics is presented,such as the defect structure in weak-light nonlinear photonic materials,light propagation dynamics in mesoscopic quantum coherent ensemble,optical nonlinearity at ultraslow group velocity of light and so on.The recent research results in new type exciton with ultraviolet weak-light nonlinear optical effect,the phase coupling with light speed control,and optical lattices induced by spatial soliton pixels of incoherent light with the light nonlinear propagation characters are also described.
Some recent work on weak-light nonlinear optics is presented,such as the defect structure in weak-light nonlinear photonic materials,light propagation dynamics in mesoscopic quantum coherent ensemble,optical nonlinearity at ultraslow group velocity of light and so on.The recent research results in new type exciton with ultraviolet weak-light nonlinear optical effect,the phase coupling with light speed control,and optical lattices induced by spatial soliton pixels of incoherent light with the light nonlinear propagation characters are also described.
2006, 30(6): 585-588.
Abstract:
To improve the beam quality of a diode-pumped Yb:YAG/YAG composite slab laser,the thermal lens effect inside the slab was analyzed.The focal lengths of the thermal lens both in thickness and width directions inside the slab were calculated.Its influenceon the resonator mode was also analyzed.A hybrid resonator was designed and the beam quality of its laser output was considered.A continuous wave kilowatts Yb:YAG/YAG composite slab laser pumped by laser diode was presented,in which the corner-pumped scheme was used.Its beam quality was measured with CCD camera.The M2 factors at width and thickness direction were better than 20 and 5 respectively,at an output power of 500W.The results show that the hybrid resonator is suitable for slab laser to obtain a good beam quality output laser.
To improve the beam quality of a diode-pumped Yb:YAG/YAG composite slab laser,the thermal lens effect inside the slab was analyzed.The focal lengths of the thermal lens both in thickness and width directions inside the slab were calculated.Its influenceon the resonator mode was also analyzed.A hybrid resonator was designed and the beam quality of its laser output was considered.A continuous wave kilowatts Yb:YAG/YAG composite slab laser pumped by laser diode was presented,in which the corner-pumped scheme was used.Its beam quality was measured with CCD camera.The M2 factors at width and thickness direction were better than 20 and 5 respectively,at an output power of 500W.The results show that the hybrid resonator is suitable for slab laser to obtain a good beam quality output laser.
2006, 30(6): 589-592.
Abstract:
In order to solve real-time metrical problem on beam wave-front of more than 500mm large aperture,a wave-front measurement system is proposed based on lens-array.Its obvious merit is to avoid machining problem of large aperture optical system,which is used to translate large aperture beam into small aperture beam.Configuration and work principle of this measurement system is introduced,and its system parameters are studied.Then it is measurement capability is analyzed according to a set of special system parameters.Two beams of 1200mm aperture are simulated,and those wave-fronts are measured separately.During this dummy experiments,system scale play an important role in wave-front measurement.The results show that the lens-array measurement can accomplish wave-front measurement of large aperture beam.Finally,its characteristic is evaluated compared with existing H-S wave-front sensor.
In order to solve real-time metrical problem on beam wave-front of more than 500mm large aperture,a wave-front measurement system is proposed based on lens-array.Its obvious merit is to avoid machining problem of large aperture optical system,which is used to translate large aperture beam into small aperture beam.Configuration and work principle of this measurement system is introduced,and its system parameters are studied.Then it is measurement capability is analyzed according to a set of special system parameters.Two beams of 1200mm aperture are simulated,and those wave-fronts are measured separately.During this dummy experiments,system scale play an important role in wave-front measurement.The results show that the lens-array measurement can accomplish wave-front measurement of large aperture beam.Finally,its characteristic is evaluated compared with existing H-S wave-front sensor.
2006, 30(6): 593-596.
Abstract:
The characteristics of cesium Stark tuned Faraday anomalous dispersion optical filter(S-FADOF) at 459nm are theoretically analyzed.The transmission spectrum of cesium S-FADOF at 459nm is calculated,then compared with that of cesium FADOF at 459nm in the same condition.The influence of different magnetic strength and temperature on the transmission spectrum of cesium S-FADOF at 459nm is analyzed.The calculated curve of the central frequency shift of the transmission spectrum of cesium S-FADOF at 459nm as a function of electric field is also given.The results show that external electric field doesn't change the structure of transmission spectrum and only causes the central frequency shift which increases with the enhancement of the electric field.
The characteristics of cesium Stark tuned Faraday anomalous dispersion optical filter(S-FADOF) at 459nm are theoretically analyzed.The transmission spectrum of cesium S-FADOF at 459nm is calculated,then compared with that of cesium FADOF at 459nm in the same condition.The influence of different magnetic strength and temperature on the transmission spectrum of cesium S-FADOF at 459nm is analyzed.The calculated curve of the central frequency shift of the transmission spectrum of cesium S-FADOF at 459nm as a function of electric field is also given.The results show that external electric field doesn't change the structure of transmission spectrum and only causes the central frequency shift which increases with the enhancement of the electric field.
2006, 30(6): 597-600.
Abstract:
In order to improve the output power and the optical-optical conversion efficiency of a laser diode pumped all-solid-state laser,a double Nd:YVO4 crystals green laser was designed.Through investigation of temperature field distribution in laser crystal and based on the transmission matrixes,the stable condition of cavity influenced by the thermal lens effects of double laser crystals was analyzed and a folded cavity of double-end-pumped double Nd:YVO4 crystals was introduced.In double-ends-pumped double Nd:YVO4 crystals green laser system,Ⅰ-type noncritical phase matching LBO crystal was used as intracavity doubling frequency.When the pump power of two diode lasers was 26.56W,the 5.5W CW 532nm green laser was got and the optical-optical conversion efficiency reached up to 20.7%.The result shows that the double laser gain mediums inserted in cavity can not only improve the optical-optical conversion efficiency of laser,but also enhance the resonant stability through the interaction of two laser crystals' thermal lens effect.
In order to improve the output power and the optical-optical conversion efficiency of a laser diode pumped all-solid-state laser,a double Nd:YVO4 crystals green laser was designed.Through investigation of temperature field distribution in laser crystal and based on the transmission matrixes,the stable condition of cavity influenced by the thermal lens effects of double laser crystals was analyzed and a folded cavity of double-end-pumped double Nd:YVO4 crystals was introduced.In double-ends-pumped double Nd:YVO4 crystals green laser system,Ⅰ-type noncritical phase matching LBO crystal was used as intracavity doubling frequency.When the pump power of two diode lasers was 26.56W,the 5.5W CW 532nm green laser was got and the optical-optical conversion efficiency reached up to 20.7%.The result shows that the double laser gain mediums inserted in cavity can not only improve the optical-optical conversion efficiency of laser,but also enhance the resonant stability through the interaction of two laser crystals' thermal lens effect.
2006, 30(6): 601-604.
Abstract:
To test 157nm silica ablating effect,the profile of micro holes on the end cross section of silica photonic crystal fiber is employed under the exposure of 157nm laser to quantitatively analyze the ablating depth and degree.The photon energy of 157nm laser is 7.9eV,can be absorbed by silica.Under 157nm laser,the defect formations in silica are accumulated to produce a large quantity of free electrons.Meanwhile,the dopants in fiber silica considerably reduce the breakdown threshold.Because the rate of single-photon absorption outclasses the rate of multi-photon absorption,it can be inferred that the mechanism of interaction between 157nm laser and silica is a process of single-photon absorption of electron-avalanche.It breaks all bonds in silica,a half of them is ionic bonds and the other half is covalent bonds.The actual ablating velocity 210nm/pulse has demonstrated that the 157nm laser can be absorbed strongly by silica material and that thermal process accompanies with the ablation,however,because the period of damage is only 20ns,the heat on the silica can be limited in a extremely small area,therefore,an ablating result with good quality can be ensured.
To test 157nm silica ablating effect,the profile of micro holes on the end cross section of silica photonic crystal fiber is employed under the exposure of 157nm laser to quantitatively analyze the ablating depth and degree.The photon energy of 157nm laser is 7.9eV,can be absorbed by silica.Under 157nm laser,the defect formations in silica are accumulated to produce a large quantity of free electrons.Meanwhile,the dopants in fiber silica considerably reduce the breakdown threshold.Because the rate of single-photon absorption outclasses the rate of multi-photon absorption,it can be inferred that the mechanism of interaction between 157nm laser and silica is a process of single-photon absorption of electron-avalanche.It breaks all bonds in silica,a half of them is ionic bonds and the other half is covalent bonds.The actual ablating velocity 210nm/pulse has demonstrated that the 157nm laser can be absorbed strongly by silica material and that thermal process accompanies with the ablation,however,because the period of damage is only 20ns,the heat on the silica can be limited in a extremely small area,therefore,an ablating result with good quality can be ensured.
2006, 30(6): 605-607.
Abstract:
In order to get the characteristics of laser ultrasound in water,a spherical ceramic hydrophone and a digital oscilloscope were used to receive,demonstrate and store the optoacoustic signal induced by a TEA CO2 pulsed laser.Later the digital signal was analyzed and handled with a computational software.The experimental results showed that:the amplitude of the signal increased with the laser pulse energy and the signal had frequency peaks at 31kHz and 62kHz below 100kHz.Furthermore the peak frequencies decreased when the laser pulse width increased.The above results mean that applicable laser ultrasound source with higher amplitude and lower frequency,which can be used in underwater communication and underwater detection,can be chosen and acquired by adjusting the energy and width of laser pulse.
In order to get the characteristics of laser ultrasound in water,a spherical ceramic hydrophone and a digital oscilloscope were used to receive,demonstrate and store the optoacoustic signal induced by a TEA CO2 pulsed laser.Later the digital signal was analyzed and handled with a computational software.The experimental results showed that:the amplitude of the signal increased with the laser pulse energy and the signal had frequency peaks at 31kHz and 62kHz below 100kHz.Furthermore the peak frequencies decreased when the laser pulse width increased.The above results mean that applicable laser ultrasound source with higher amplitude and lower frequency,which can be used in underwater communication and underwater detection,can be chosen and acquired by adjusting the energy and width of laser pulse.
2006, 30(6): 608-610,613.
Abstract:
In order to measure the object's position and velocity,the method of counting pulse with analog interpolation is used to measure the distance,and the method of differential coefficient of the fitting curve based on least-square curve fitting that takes the exponential function is used to measure velocity,and the method of orientating facula with quadrant detector is selected to measure the orientation angles in the pulsed lidar measuring system.Computer simulation is performed with the MATLAB/SIMULINK.As a result,the distance precision is less than 0.01m,the velocity error is smaller than 0.02m/s.It can be concluded that the information measuring technology of pulse lidar is reliable.
In order to measure the object's position and velocity,the method of counting pulse with analog interpolation is used to measure the distance,and the method of differential coefficient of the fitting curve based on least-square curve fitting that takes the exponential function is used to measure velocity,and the method of orientating facula with quadrant detector is selected to measure the orientation angles in the pulsed lidar measuring system.Computer simulation is performed with the MATLAB/SIMULINK.As a result,the distance precision is less than 0.01m,the velocity error is smaller than 0.02m/s.It can be concluded that the information measuring technology of pulse lidar is reliable.
2006, 30(6): 614-617.
Abstract:
Hydroxyapatite(HA) is one of bioactive ceramics with best bioactivity at present.The techniques for producing its film have become one of the hot points in the material research.As a new technique for changing the surface properties,laser cladding shows the unique advantages for producing HA bioceramic coatings.The quality of the coating is much better than that of the coating produced by other techniques.The characteristics of microstructure and properties of the coating by laser cladding and their influencing factors are reviewed.The effects on the qualities of the coating of laser parameters,reactant composition,rare earth element and gradient coating are analyzed in detail.The future application trend is also prospected.
Hydroxyapatite(HA) is one of bioactive ceramics with best bioactivity at present.The techniques for producing its film have become one of the hot points in the material research.As a new technique for changing the surface properties,laser cladding shows the unique advantages for producing HA bioceramic coatings.The quality of the coating is much better than that of the coating produced by other techniques.The characteristics of microstructure and properties of the coating by laser cladding and their influencing factors are reviewed.The effects on the qualities of the coating of laser parameters,reactant composition,rare earth element and gradient coating are analyzed in detail.The future application trend is also prospected.
2006, 30(6): 618-620,624.
Abstract:
For the purpose of jamming the amplitude modulation reticle system,two methods of active jamming of infrared seeker are analyzed by using numerical simulation based on the operation principle of an infrared seeker with amplitude modulation reticle.The results show that the jamming source with a slow variation of amplitude will warp the target's azimuth received by the seeker.But it can not make the target escape from the scout of the seeker.At a repetition rate nearly equal to the carrier frequency of the reticle system,the jamming source will disturb the target's signal received by the seeker,and make the seeker lose the target.If the intensity of the jamming source nearly equals to that of target's radiation,the jamming can be achieved.
For the purpose of jamming the amplitude modulation reticle system,two methods of active jamming of infrared seeker are analyzed by using numerical simulation based on the operation principle of an infrared seeker with amplitude modulation reticle.The results show that the jamming source with a slow variation of amplitude will warp the target's azimuth received by the seeker.But it can not make the target escape from the scout of the seeker.At a repetition rate nearly equal to the carrier frequency of the reticle system,the jamming source will disturb the target's signal received by the seeker,and make the seeker lose the target.If the intensity of the jamming source nearly equals to that of target's radiation,the jamming can be achieved.
2006, 30(6): 621-624.
Abstract:
For laser powder micro-deposition process,the bonding between the deposited materials and the substrates is crucial to the quality of the deposited components.In order to fabricate fine thin parts with uniform thickness and good bonding strength directly,the effect of processing parameters on wall thickness uniformity and stability of the process during laser micro-deposition of metallic powder from StelliteF alloy is investigated experimentally.The observation and analysis of the cross-section and the microstructure of the deposited thin walls indicate that,the change of heat dissipation condition during deposition influences the wall thickness uniformity.Under reasonable processing parameters,thin wall parts with surface roughness(Ra) as low as 10μm,the wall thickness as thin as 0.4mm and metallurgically sound structure can be deposited directly.It indicates that laser micro-deposition of metallic powder has a bright prospect in laser surface modification of small parts and direct fabrication of fine and precise components.
For laser powder micro-deposition process,the bonding between the deposited materials and the substrates is crucial to the quality of the deposited components.In order to fabricate fine thin parts with uniform thickness and good bonding strength directly,the effect of processing parameters on wall thickness uniformity and stability of the process during laser micro-deposition of metallic powder from StelliteF alloy is investigated experimentally.The observation and analysis of the cross-section and the microstructure of the deposited thin walls indicate that,the change of heat dissipation condition during deposition influences the wall thickness uniformity.Under reasonable processing parameters,thin wall parts with surface roughness(Ra) as low as 10μm,the wall thickness as thin as 0.4mm and metallurgically sound structure can be deposited directly.It indicates that laser micro-deposition of metallic powder has a bright prospect in laser surface modification of small parts and direct fabrication of fine and precise components.
2006, 30(6): 625-627.
Abstract:
To improve the quality of excimer laser drilling,the factors affecting the drilling quality with excimer laser system are analyzed.Based on the analysis,a new method for micro-drilling is put forward and an optical system is designed.The experimental result shows that when the excimer laser with wavelength of 248nm drill on the polymethyl methacrylate with this system,the figure of the micro-hole is regular and the quality of the holes is improved.The system improves the speed and the quality of micro-drilling and is feasible in industrial areas.
To improve the quality of excimer laser drilling,the factors affecting the drilling quality with excimer laser system are analyzed.Based on the analysis,a new method for micro-drilling is put forward and an optical system is designed.The experimental result shows that when the excimer laser with wavelength of 248nm drill on the polymethyl methacrylate with this system,the figure of the micro-hole is regular and the quality of the holes is improved.The system improves the speed and the quality of micro-drilling and is feasible in industrial areas.
2006, 30(6): 628-630,635.
Abstract:
In order to analyze and restrain the multi-perturbation in the ultra long-haul multi-channel dispersion managed soliton(DMS) transmission system,the effect of perturbation including the amplifier spontaneous emission(ASE) noise,intra-symbol interference(ISI) between the channels is analyzed by variational method.The control capability of inline filter in restraining the frequency shifting and timing jitter of DMSis also studied.The analysis results indicate that the filters can stabilize amplitude and pulse-width of DMS and restraining the effects of multi-perturbations.There exists an optimal configure scheme of filter strength and parameters of DMS.The perturbation of cross-phase modulation(XPM)-ASE is obviously decreased by filter,then the perturbation of ASE noise and XPM.The results and the optimal scheme of filter control can be taken as a reference in estimating performance of high-speed and big capacity system.
In order to analyze and restrain the multi-perturbation in the ultra long-haul multi-channel dispersion managed soliton(DMS) transmission system,the effect of perturbation including the amplifier spontaneous emission(ASE) noise,intra-symbol interference(ISI) between the channels is analyzed by variational method.The control capability of inline filter in restraining the frequency shifting and timing jitter of DMSis also studied.The analysis results indicate that the filters can stabilize amplitude and pulse-width of DMS and restraining the effects of multi-perturbations.There exists an optimal configure scheme of filter strength and parameters of DMS.The perturbation of cross-phase modulation(XPM)-ASE is obviously decreased by filter,then the perturbation of ASE noise and XPM.The results and the optimal scheme of filter control can be taken as a reference in estimating performance of high-speed and big capacity system.
2006, 30(6): 631-635.
Abstract:
In order to increase the precision and safety of the corneal ablation refractive surgery,two mathematical models for corneal ablation were given,one was for spherical myopia and compound myopic astigmatism,the other was for spherical hyperopia and compound hyperopic astigmatism,Based on both the mathematical models,the flying-spot scanning algorithm was put forward.The mathematical models and the algorithm were applied to ophthalmic excimer laser system.Eighty-nine eyes underwent laser in situ keratomileusis(LASIK) using the models and algorithm,including 88 eyes with spherical myopia and compound myopic astigmatism and 1 with compound hyperopic astigmatism.The lightsight of 80.7% of the nake eyes increased upto 0.8.It can be concluded that the mathematical models and the algorithm are precise and safe and the laser cornea surgery is satisfactory.
In order to increase the precision and safety of the corneal ablation refractive surgery,two mathematical models for corneal ablation were given,one was for spherical myopia and compound myopic astigmatism,the other was for spherical hyperopia and compound hyperopic astigmatism,Based on both the mathematical models,the flying-spot scanning algorithm was put forward.The mathematical models and the algorithm were applied to ophthalmic excimer laser system.Eighty-nine eyes underwent laser in situ keratomileusis(LASIK) using the models and algorithm,including 88 eyes with spherical myopia and compound myopic astigmatism and 1 with compound hyperopic astigmatism.The lightsight of 80.7% of the nake eyes increased upto 0.8.It can be concluded that the mathematical models and the algorithm are precise and safe and the laser cornea surgery is satisfactory.
2006, 30(6): 636-637,660.
Abstract:
The polarization state of input laser induced by the change of transmitted distance is studied.From theory analysis and experiment data,the polarization of input laser can be changed by wedge cholesteric liquid crystal cell through continual adjusting the transmitted distance.The input linearly polarized laser is changed to circularly polarized light.This change is not depent on the first polarize angle.The results show that wedge cholesteric liquid crystal cell can be used in the design and analysis of liquid crystal depolarizer.
The polarization state of input laser induced by the change of transmitted distance is studied.From theory analysis and experiment data,the polarization of input laser can be changed by wedge cholesteric liquid crystal cell through continual adjusting the transmitted distance.The input linearly polarized laser is changed to circularly polarized light.This change is not depent on the first polarize angle.The results show that wedge cholesteric liquid crystal cell can be used in the design and analysis of liquid crystal depolarizer.
2006, 30(6): 638-642,656.
Abstract:
The application of light emitting diode(LED) therapy in biology and medicine is summarized,which focuses on the experiments in animal model,animal cells and clinical research.The advantages and disadvantages of LED therapy are compared with those of the other light sources in the view of safety,reliability and low cast.It can be sure that LED therapy must have a wide foreground in biology,medicine and commercial products.
The application of light emitting diode(LED) therapy in biology and medicine is summarized,which focuses on the experiments in animal model,animal cells and clinical research.The advantages and disadvantages of LED therapy are compared with those of the other light sources in the view of safety,reliability and low cast.It can be sure that LED therapy must have a wide foreground in biology,medicine and commercial products.
2006, 30(6): 643-646.
Abstract:
Several methods and theory of THz imaging as well as late results of the researchers in Russia and Korea are introduced.At present,THz is being developed towards 3-D imaging.
Several methods and theory of THz imaging as well as late results of the researchers in Russia and Korea are introduced.At present,THz is being developed towards 3-D imaging.
2006, 30(6): 647-649,666.
Abstract:
To investigate the propagation of acoustic surface waves in a cylindrical coating-substrate system,a finite element algorithm is put forward to simulate laser inducing acoustic surface wave in cylindrical coating-substrate system based on the thermoelastic mechanism.Using this algorithm,the waveforms of laser-induced acoustic waves on the aluminum(coating)/nickel(substrate) and nickel(coating)/aluminum(substrate) system are simulated.The results show that surface acoustic wave on the cylindrical coating-substrate system is dispersive.When surface acoustic waves are propagating along the cylindrical structure,there exists geometry dispersion,which makes the dispersion property of the cylindrical coating system more complex than that of a plate coating system.As a result,there is not simple rule for predicating the dispersive property of surface acoustic waves on cylindrical coating-substrate system.
To investigate the propagation of acoustic surface waves in a cylindrical coating-substrate system,a finite element algorithm is put forward to simulate laser inducing acoustic surface wave in cylindrical coating-substrate system based on the thermoelastic mechanism.Using this algorithm,the waveforms of laser-induced acoustic waves on the aluminum(coating)/nickel(substrate) and nickel(coating)/aluminum(substrate) system are simulated.The results show that surface acoustic wave on the cylindrical coating-substrate system is dispersive.When surface acoustic waves are propagating along the cylindrical structure,there exists geometry dispersion,which makes the dispersion property of the cylindrical coating system more complex than that of a plate coating system.As a result,there is not simple rule for predicating the dispersive property of surface acoustic waves on cylindrical coating-substrate system.
2006, 30(6): 650-652,663.
Abstract:
The change of the output power and the frequency of the light source of an optical fiber interferometer seriously affects the output of the interferometer.In order to get high output accuracy and stability from the optical fiber interferometer,the operation amplifier with high S/N,and a semiconductor cooler were used.A laser power driving system was designed.Through theoretical and experimental analysis,it was proved to provide laser diode(LD) with high stability and,high temperature controlling precision of ±0.01℃.The cooling driving current could reach 800mA.At the same time,it provides current control with high stability and constant control over output power,which assures the precision of the controlled wavelength to be ±0.1nm.The maximum LD driving current reaches 180mA,and the output curren stability could be kept among 10-4~10-5.The experimental data indicate the method is not only simple,but also highly accurate and stable in terms of temperature control.The application maintains the output wavelength of the laser diode at a constant level and assures the measure accuracy in optical fiber interferometer sensors(OFIS) and optical communication.
The change of the output power and the frequency of the light source of an optical fiber interferometer seriously affects the output of the interferometer.In order to get high output accuracy and stability from the optical fiber interferometer,the operation amplifier with high S/N,and a semiconductor cooler were used.A laser power driving system was designed.Through theoretical and experimental analysis,it was proved to provide laser diode(LD) with high stability and,high temperature controlling precision of ±0.01℃.The cooling driving current could reach 800mA.At the same time,it provides current control with high stability and constant control over output power,which assures the precision of the controlled wavelength to be ±0.1nm.The maximum LD driving current reaches 180mA,and the output curren stability could be kept among 10-4~10-5.The experimental data indicate the method is not only simple,but also highly accurate and stable in terms of temperature control.The application maintains the output wavelength of the laser diode at a constant level and assures the measure accuracy in optical fiber interferometer sensors(OFIS) and optical communication.
2006, 30(6): 653-656.
Abstract:
Optical crosstalk imposes a major limit on the practical implementation of optical cross-connects(OXCs).Intraband crosstalk characteristics of three typical OXC nodes based on dilated Benes(DB) network and generally modified dilated Benes(GMDB) network are studied.Results show that OXC composed by DB and GMDB network can remove the first order crosstalk successfully.At the same time,the power penalty induced by intraband crosstalk is studied through numerical simulation.Compared with DB network,GMDB network can eliminates crosstalk effectively.The crosstalk level of optical devices required in GMDB network is about 5dB lower than that in DB network to keep the power penalty below 1dB at the bit error rate of 10-9,which indicates that the OXC structure plays an important role in eliminating optical crosstalk.
Optical crosstalk imposes a major limit on the practical implementation of optical cross-connects(OXCs).Intraband crosstalk characteristics of three typical OXC nodes based on dilated Benes(DB) network and generally modified dilated Benes(GMDB) network are studied.Results show that OXC composed by DB and GMDB network can remove the first order crosstalk successfully.At the same time,the power penalty induced by intraband crosstalk is studied through numerical simulation.Compared with DB network,GMDB network can eliminates crosstalk effectively.The crosstalk level of optical devices required in GMDB network is about 5dB lower than that in DB network to keep the power penalty below 1dB at the bit error rate of 10-9,which indicates that the OXC structure plays an important role in eliminating optical crosstalk.
2006, 30(6): 657-660.
Abstract:
Acquiring 3-D surface information by means of laser triangulation is a kind of active vision measurement.In order to improve the measurement speed,a fast 3-D information acquisition and surface reconstruction system based on smart camera and laser triangulation was presented.The hardware construction and data processing flow of the system was introduced.Because of applying of the digital signal processor(DSP) and parallel processing,the result of experiment shows that the speed of acquisition can reach 5600 dots/s.
Acquiring 3-D surface information by means of laser triangulation is a kind of active vision measurement.In order to improve the measurement speed,a fast 3-D information acquisition and surface reconstruction system based on smart camera and laser triangulation was presented.The hardware construction and data processing flow of the system was introduced.Because of applying of the digital signal processor(DSP) and parallel processing,the result of experiment shows that the speed of acquisition can reach 5600 dots/s.
2006, 30(6): 661-663.
Abstract:
The accident damage of the present semiconductor laser constant current source often damages the expensive semiconductor laser directly.In order to protect the laser working normally and save the complex high-speed protection circuit,the synchronously adjustable constant current tube tandem type laser constant current source is designed.It adopts two constant current tubes to be adjusted synchronously.Both of them can be kept working in the constant current area,and their output currents are equivalent to a large extent in the whole adjustment range.When the laser is working in 400mA,the current aggrandizement caused by the momentary damage of any transistors is only 15mA.It is concluded that the laser constant current source made of the synchronously adjustable tandem constant current tube has high constant current characteristic and protective property.
The accident damage of the present semiconductor laser constant current source often damages the expensive semiconductor laser directly.In order to protect the laser working normally and save the complex high-speed protection circuit,the synchronously adjustable constant current tube tandem type laser constant current source is designed.It adopts two constant current tubes to be adjusted synchronously.Both of them can be kept working in the constant current area,and their output currents are equivalent to a large extent in the whole adjustment range.When the laser is working in 400mA,the current aggrandizement caused by the momentary damage of any transistors is only 15mA.It is concluded that the laser constant current source made of the synchronously adjustable tandem constant current tube has high constant current characteristic and protective property.
2006, 30(6): 664-666.
Abstract:
A LD power supply for pumping the monolithic laser is developed and driven by constant current circuit.Software monitoring is applied to test and adjust long period stability and fault of current.Temperature adjustment arithmetic of fuzzy and proportional-integral-derivative(PID) control is used to gain small overshoot and high control precision.Basic PID arithmetic is simplified by using a subsection chosen value to improve the operation speed more than ten times.Continuously frequency adjustable laser is realized in a certain temperature range,whose current stability is less than 2mA,lasting temperature fluctuation is below 0.1℃.
A LD power supply for pumping the monolithic laser is developed and driven by constant current circuit.Software monitoring is applied to test and adjust long period stability and fault of current.Temperature adjustment arithmetic of fuzzy and proportional-integral-derivative(PID) control is used to gain small overshoot and high control precision.Basic PID arithmetic is simplified by using a subsection chosen value to improve the operation speed more than ten times.Continuously frequency adjustable laser is realized in a certain temperature range,whose current stability is less than 2mA,lasting temperature fluctuation is below 0.1℃.
2006, 30(6): 667-669,672.
Abstract:
Phase unwrapping is an important step for precise phase measurement in optical interferometric techniques.Due to the effect of noise and undersampled region,an accurate phase unwrapping has been quite difficult.A new phase unwrapping algorithm based on phase second difference and minimum cost flow algorithm is presented.Computer simulation shows:it can avoid local incomplete unwrapping problem that interlaced cuts produce closed regions in branch cut algorithm and reduce the errors caused by least square unwrapping algorithm.Comparing with the unweighted minimum cost flow algorithm,it also improves the phase unwrapping precision.The phase unwrapping result on real data in 3-D shape measurement verifies the validity of the algorithm.
Phase unwrapping is an important step for precise phase measurement in optical interferometric techniques.Due to the effect of noise and undersampled region,an accurate phase unwrapping has been quite difficult.A new phase unwrapping algorithm based on phase second difference and minimum cost flow algorithm is presented.Computer simulation shows:it can avoid local incomplete unwrapping problem that interlaced cuts produce closed regions in branch cut algorithm and reduce the errors caused by least square unwrapping algorithm.Comparing with the unweighted minimum cost flow algorithm,it also improves the phase unwrapping precision.The phase unwrapping result on real data in 3-D shape measurement verifies the validity of the algorithm.
2006, 30(6): 670-672.
Abstract:
To improve the symmetry of emergent beams of a polarization prism,based on the Wallaston prism,the emergent face is inclined with an appropriate angle,so that the symmetry which the beam-splitting angle relative to the incident light direction can be ensured in the case of a certain structure angle.Taking the 589.3nm sodium yellow light for example,the relation formula among the obliquity of the emergent face,the structure angle of the prism and the beam-splitting angle are deduced,and the change trend of the beam-splitting angle along with the emergent face is also analyzed.Two correlative designs are presented at the same time.The testing results indicate that the symmetry is excellent and the experiment value is almost identical with the theoretical value which shows this polarization prism is positively an ideal symmetric beam-splitting polarization device.
To improve the symmetry of emergent beams of a polarization prism,based on the Wallaston prism,the emergent face is inclined with an appropriate angle,so that the symmetry which the beam-splitting angle relative to the incident light direction can be ensured in the case of a certain structure angle.Taking the 589.3nm sodium yellow light for example,the relation formula among the obliquity of the emergent face,the structure angle of the prism and the beam-splitting angle are deduced,and the change trend of the beam-splitting angle along with the emergent face is also analyzed.Two correlative designs are presented at the same time.The testing results indicate that the symmetry is excellent and the experiment value is almost identical with the theoretical value which shows this polarization prism is positively an ideal symmetric beam-splitting polarization device.
