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RSS2011 Vol. 35, No. 6
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2011, 35(6): 721-724.
doi: 10.3969/j.issn.1001-3806.2011.06.001
[Abstract]
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Abstract:
Single-pulse and continuous-pulse ablation was carried on bronze-bonded diamond grinding wheels with 300W xenon lamp pumped YAG pulsed laser and 80W acoustic-optic Q-switched YAG pulsed laser respectively, in order to choose appropriate laser equipment and parameters for improving the efficiency and accuracy of grinding wheel turing and dressing. The morphology of the wheel surface after laser irradiation was analyzed by means of stereo microscope. Through theoretical derivation, a formula was obtained to reduce the option range of laser and parameters effectively under the premise of guaranteeing the accuracy and efficiency. It helps choose appropriate laser parameters for turing and dressing different grinding wheels more effectively. Compared with xenon lamp pumped YAG pulsed laser, acoustic-optic Q-switched YAG pulsed laser has lower single pulse energy, higher pulse frequency, narrower pulse width, higher peak power, so it is more suitable for high accuracy and efficiency turing and dressing of grinding wheels.
Single-pulse and continuous-pulse ablation was carried on bronze-bonded diamond grinding wheels with 300W xenon lamp pumped YAG pulsed laser and 80W acoustic-optic Q-switched YAG pulsed laser respectively, in order to choose appropriate laser equipment and parameters for improving the efficiency and accuracy of grinding wheel turing and dressing. The morphology of the wheel surface after laser irradiation was analyzed by means of stereo microscope. Through theoretical derivation, a formula was obtained to reduce the option range of laser and parameters effectively under the premise of guaranteeing the accuracy and efficiency. It helps choose appropriate laser parameters for turing and dressing different grinding wheels more effectively. Compared with xenon lamp pumped YAG pulsed laser, acoustic-optic Q-switched YAG pulsed laser has lower single pulse energy, higher pulse frequency, narrower pulse width, higher peak power, so it is more suitable for high accuracy and efficiency turing and dressing of grinding wheels.
2011, 35(6): 725-733.
doi: 10.3969/j.issn.1001-3806.2011.06.002
Abstract:
The present research progress of pumping and coupling methods of high power solid-state lasers such as slab laser, disk laser and heat capacity laser was summarized. The pumping and coupling technologies of these solid-state lasers were analyzed and compared from the point of overcoming heat effect. The future trend of pumping and coupling technologies was introduced.
The present research progress of pumping and coupling methods of high power solid-state lasers such as slab laser, disk laser and heat capacity laser was summarized. The pumping and coupling technologies of these solid-state lasers were analyzed and compared from the point of overcoming heat effect. The future trend of pumping and coupling technologies was introduced.
2011, 35(6): 734-737,755.
doi: 10.3969/j.issn.1001-3806.2011.06.003
Abstract:
In order to carve 3-D deep images on hard material, after analyzing the relationship of 3-D image space shading, a new algorithm was put forward for carving real 3-D images on solid material by means of laser ablation. At first, the 3-D image was mapped to a big space box based on the box algorithm. Then complete envelope points of STL(stereo lithography, a 3-D model file format) can be obtained with rays parallel to the z-axis intersecting the STL triangular facets. At the same time, by normalizing the points to the small space boxes and marking the corresponding small shaded space boxes, the data for carving solid material were obtained. The algorithm was used in a 3-D laser carving system to deal with a STL in 268mm 422mm 253mm including 130000 facets, it took 2s~5s. The results show that the algorithm is practical and efficient.
In order to carve 3-D deep images on hard material, after analyzing the relationship of 3-D image space shading, a new algorithm was put forward for carving real 3-D images on solid material by means of laser ablation. At first, the 3-D image was mapped to a big space box based on the box algorithm. Then complete envelope points of STL(stereo lithography, a 3-D model file format) can be obtained with rays parallel to the z-axis intersecting the STL triangular facets. At the same time, by normalizing the points to the small space boxes and marking the corresponding small shaded space boxes, the data for carving solid material were obtained. The algorithm was used in a 3-D laser carving system to deal with a STL in 268mm 422mm 253mm including 130000 facets, it took 2s~5s. The results show that the algorithm is practical and efficient.
2011, 35(6): 738-741,791.
doi: 10.3969/j.issn.1001-3806.2011.06.004
Abstract:
In order to improve the symbol detection performance of an atmospheric laser optical frequency division multiplexing(OFDM) receiver, semi-blind estimation was carried out in an atmospheric laser OFDM time-varying channel by means of a mixed particle filtering algorithm. Comparing with the existing time-varying channel estimation based on pilot, this method can effectively improve symbol detection performance at receiver. Finally, MATLAB simulation proved the effectiveness of this new method. Obtained results show that this method can decrease bit error ratio to one magnitude at receiver under the same signal-to-noise ratio compared to other methods.
In order to improve the symbol detection performance of an atmospheric laser optical frequency division multiplexing(OFDM) receiver, semi-blind estimation was carried out in an atmospheric laser OFDM time-varying channel by means of a mixed particle filtering algorithm. Comparing with the existing time-varying channel estimation based on pilot, this method can effectively improve symbol detection performance at receiver. Finally, MATLAB simulation proved the effectiveness of this new method. Obtained results show that this method can decrease bit error ratio to one magnitude at receiver under the same signal-to-noise ratio compared to other methods.
2011, 35(6): 742-744,769.
doi: 10.3969/j.issn.1001-3806.2011.06.005
Abstract:
To detect the quality of pure milk rapidly, its spectral characteristics were analyzed combining 3-D fluorescent spectra with multi-peak fitting method, and its main compositions were obtained. The results show that its excitation spectrum ranges from 250nm to 310nm, and the peak wavelength is 290nm. The main emission spectrum ranges from 280nm to 500nm with the peak adjacent to 330nm.Meanwhile, the fluorescent spectrum has five spectral peaks(Ⅰ~Ⅴ), where peakⅠis generated by some proteins under the influence of lactose, peak Ⅱis generated by fat and vitamin E jointly, peak Ⅲ is generated by protein directly, peak Ⅳ is generated by some proteins under some unknown influence, and peak Ⅴ is generated jointly by microelements including vitamin A, vitamin B1, and B6. The study results provide some basic principles for studying milk composition with fluorescent spectroscopy.
To detect the quality of pure milk rapidly, its spectral characteristics were analyzed combining 3-D fluorescent spectra with multi-peak fitting method, and its main compositions were obtained. The results show that its excitation spectrum ranges from 250nm to 310nm, and the peak wavelength is 290nm. The main emission spectrum ranges from 280nm to 500nm with the peak adjacent to 330nm.Meanwhile, the fluorescent spectrum has five spectral peaks(Ⅰ~Ⅴ), where peakⅠis generated by some proteins under the influence of lactose, peak Ⅱis generated by fat and vitamin E jointly, peak Ⅲ is generated by protein directly, peak Ⅳ is generated by some proteins under some unknown influence, and peak Ⅴ is generated jointly by microelements including vitamin A, vitamin B1, and B6. The study results provide some basic principles for studying milk composition with fluorescent spectroscopy.
2011, 35(6): 745-747,751.
doi: 10.3969/j.issn.1001-3806.2011.06.006
Abstract:
In order to study the output characteristics of a corner cube array resonator, the resonator was constructed with a corner cube array(CCA) and a planar mirror as rear mirror and output mirror respectively. Its near-field and far-field mode distribution was demonstrated through numerical simulation. The coherent output of the resonator was theoretically analyzed. Furthermore, the mode distribution of a Nd:glass laser with this type of resonator was obtained in experiments. The results show that the simulated mode distribution agrees with the experimental results. The profile of the near-field mode distribution is hexagonal and similar to the geometry of the CCA. There is a high pulse in the middle of the far-field beam spot with many low pulses around it. The quantity and layout of the pulses in each circle are the same as those of the corresponding corner cubes in the CCA. The results also show that it's feasible to achieve coherent laser output with a corner cube array resonator.
In order to study the output characteristics of a corner cube array resonator, the resonator was constructed with a corner cube array(CCA) and a planar mirror as rear mirror and output mirror respectively. Its near-field and far-field mode distribution was demonstrated through numerical simulation. The coherent output of the resonator was theoretically analyzed. Furthermore, the mode distribution of a Nd:glass laser with this type of resonator was obtained in experiments. The results show that the simulated mode distribution agrees with the experimental results. The profile of the near-field mode distribution is hexagonal and similar to the geometry of the CCA. There is a high pulse in the middle of the far-field beam spot with many low pulses around it. The quantity and layout of the pulses in each circle are the same as those of the corresponding corner cubes in the CCA. The results also show that it's feasible to achieve coherent laser output with a corner cube array resonator.
2011, 35(6): 748-751.
doi: 10.3969/j.issn.1001-3806.2011.06.007
Abstract:
The coupling of the surface modes and the fundamental modes is the root of the disappearance of coupling points between the two cores of the hollow dual-core photonic crystal fibers. In order to study the mechanism of the appearance and control of surface modes, the full vector finite element method and the plane wave expansion method were used to study the effect of the silica ring or the core radius on the surface modes and the change of the uncoupling point. The numerical simulation shows that with the same core radius, the uncoupling point moves to longer wavelength with the increase of the normalized thickness of the silica ring. And the optimal range of core radius that is free of surface modes is from 0.9 to 1.0 when the normalized thickness of the silica ring is set to 1. The results provide theoretical evidence to design the novel hollow dual-core photonic crystal fibers, enriching and consummating the theoretical foundation for the hollow dual-core photonic crystal fibers.
The coupling of the surface modes and the fundamental modes is the root of the disappearance of coupling points between the two cores of the hollow dual-core photonic crystal fibers. In order to study the mechanism of the appearance and control of surface modes, the full vector finite element method and the plane wave expansion method were used to study the effect of the silica ring or the core radius on the surface modes and the change of the uncoupling point. The numerical simulation shows that with the same core radius, the uncoupling point moves to longer wavelength with the increase of the normalized thickness of the silica ring. And the optimal range of core radius that is free of surface modes is from 0.9 to 1.0 when the normalized thickness of the silica ring is set to 1. The results provide theoretical evidence to design the novel hollow dual-core photonic crystal fibers, enriching and consummating the theoretical foundation for the hollow dual-core photonic crystal fibers.
2011, 35(6): 752-755.
doi: 10.3969/j.issn.1001-3806.2011.06.008
Abstract:
In order to discover the effect of a laser quenched substrate on the surface morphology of Cr-plating coatings, the substrate was quenched by laser discretely and then Cr-coatings were plated on the surface. There appeared periodical strips alternating with dense and loose ball-like microstructure on the surface morphology in accordance with discrete substrate. The dense and loose strips correspond with original and laser quenched zone respectively. With the help of high resolution scanning electron microscope, the chemically-etching substrate and ion etching methods were used to analyze the microstructure morphologies on the Cr-coating interface and along the thickness direction respectively. The results show that the mechanism of the periodical morphological formation of Cr-coating is that the substrate discrete characteristic is transferred to coating surface by means of the periodical characteristic of coating interface and differential Cr-coating growth mode.
In order to discover the effect of a laser quenched substrate on the surface morphology of Cr-plating coatings, the substrate was quenched by laser discretely and then Cr-coatings were plated on the surface. There appeared periodical strips alternating with dense and loose ball-like microstructure on the surface morphology in accordance with discrete substrate. The dense and loose strips correspond with original and laser quenched zone respectively. With the help of high resolution scanning electron microscope, the chemically-etching substrate and ion etching methods were used to analyze the microstructure morphologies on the Cr-coating interface and along the thickness direction respectively. The results show that the mechanism of the periodical morphological formation of Cr-coating is that the substrate discrete characteristic is transferred to coating surface by means of the periodical characteristic of coating interface and differential Cr-coating growth mode.
2011, 35(6): 756-760.
Abstract:
Mid-infrared all-solid-state optical parametric oscillator, due to wide tuning range, low threshold, high efficiency, high repetition rate and the advantages of miniaturization, have widespread optoelectronic countermeasures, laser radar, laser ranging, spectral measurements and the areas of environmental monitoring. In recent years there has been increasing interest in the mid-infrared OPO. This article focuses on research and progress of middle-infrared single resonant OPO（ISRO）, which is based on birefringent phase-matching crystals (such as KTA, KTP) and quasi-phase matching crystals (such as PPKTP, PPKTA, PPLN). We also discuses the development trend of ISRO.
Mid-infrared all-solid-state optical parametric oscillator, due to wide tuning range, low threshold, high efficiency, high repetition rate and the advantages of miniaturization, have widespread optoelectronic countermeasures, laser radar, laser ranging, spectral measurements and the areas of environmental monitoring. In recent years there has been increasing interest in the mid-infrared OPO. This article focuses on research and progress of middle-infrared single resonant OPO（ISRO）, which is based on birefringent phase-matching crystals (such as KTA, KTP) and quasi-phase matching crystals (such as PPKTP, PPKTA, PPLN). We also discuses the development trend of ISRO.
2011, 35(6): 761-764.
doi: 10.3969/j.issn.1001-3806.2011.06.010
Abstract:
In order to analyze the temperature characteristics in the stimulated emission of a CTH:YAG laser, taking the quasi-three-level characteristics of CTH:YAG and the influence of Tm-Ho quasi-thermal equilibrium system into account, a so-called relative oscillation efficiency parameter was defined based on the photon density in the rate equation. The numerical simulation results show that relative oscillation efficiency is a nonlinear decreasing function of temperature, and there is a stop temperature at which the stimulated emission can not happen. The stop temperature is in direct proportion to the energy stored by Tm-Ho quasi-thermal equilibrium system, and relative oscillation efficiency also augments with the stored energy rising. The analysis provides a theoretical evidence of the temperature characteristics of CTH:YAG, and is useful for optimizing the output pulse.
In order to analyze the temperature characteristics in the stimulated emission of a CTH:YAG laser, taking the quasi-three-level characteristics of CTH:YAG and the influence of Tm-Ho quasi-thermal equilibrium system into account, a so-called relative oscillation efficiency parameter was defined based on the photon density in the rate equation. The numerical simulation results show that relative oscillation efficiency is a nonlinear decreasing function of temperature, and there is a stop temperature at which the stimulated emission can not happen. The stop temperature is in direct proportion to the energy stored by Tm-Ho quasi-thermal equilibrium system, and relative oscillation efficiency also augments with the stored energy rising. The analysis provides a theoretical evidence of the temperature characteristics of CTH:YAG, and is useful for optimizing the output pulse.
2011, 35(6): 765-769.
doi: 10.3969/j.issn.1001-3806.2011.06.011
Abstract:
Because photo-thermo-refractive(PTR) glass has high photo-sensitivity in the UV band, and high transmittance in the near-IR band, volume Bragg gratings(VBGs)recorded in PTR glass are widely used in high-power lasers. Recent progress of spectral beam combination of fiber lasers based on VBGs was reviewed. The theory of VBGs recorded in PTR glass and the basic principle of five kinds of spectral beam combination schemes were introduced, including spectral beam combination based on single VBG,cascaded VBGs and multiplexed VBGs, common-cavity spectral beam combination and coherent and spectral beam combination based on VBGs. The advantages and disadvantages of these schemes were analyzed. At last, the problems of each beam combination were discussed.
Because photo-thermo-refractive(PTR) glass has high photo-sensitivity in the UV band, and high transmittance in the near-IR band, volume Bragg gratings(VBGs)recorded in PTR glass are widely used in high-power lasers. Recent progress of spectral beam combination of fiber lasers based on VBGs was reviewed. The theory of VBGs recorded in PTR glass and the basic principle of five kinds of spectral beam combination schemes were introduced, including spectral beam combination based on single VBG,cascaded VBGs and multiplexed VBGs, common-cavity spectral beam combination and coherent and spectral beam combination based on VBGs. The advantages and disadvantages of these schemes were analyzed. At last, the problems of each beam combination were discussed.
2011, 35(6): 770-772,794.
doi: 10.3969/j.issn.1001-3806.2011.06.012
Abstract:
In order to actualize ballistic trajectory simulation in a laser simulation training system, on the basis of the beam deflexion character of dual-wedge, the laser beam was deflected by control turning angle of the dual-wedge. The formula for controlling the turning angle of dual-wedge was also deduced from the optical ray refraction theorem. The experimental results indicate that the laser beam pointing accuracy of the system is higher than 1mrad. This system can be used for force-on-force engagement training of direct heavy weapons such as tanks.
In order to actualize ballistic trajectory simulation in a laser simulation training system, on the basis of the beam deflexion character of dual-wedge, the laser beam was deflected by control turning angle of the dual-wedge. The formula for controlling the turning angle of dual-wedge was also deduced from the optical ray refraction theorem. The experimental results indicate that the laser beam pointing accuracy of the system is higher than 1mrad. This system can be used for force-on-force engagement training of direct heavy weapons such as tanks.
2011, 35(6): 773-774,832.
doi: 10.3969/j.issn.1001-3806.2011.06.013
Abstract:
In order to study effect of incident angles on IR polarizing property of Co-Al2O3 film, Co was implanted into the pores of anodic alumina by means of electroplating. Its transmittance spectrum was measured with UV-3101PC spectral photometer, and its polarizing spectrum was tested at the incident angles of 30 and 45 respectively. The experimental result indicates that such anodic alumina film with Co columns has good transmittance and extinction ratio in the near-infrared waveband, and the extinction ratio improves notably with increase of the incident angle.
In order to study effect of incident angles on IR polarizing property of Co-Al2O3 film, Co was implanted into the pores of anodic alumina by means of electroplating. Its transmittance spectrum was measured with UV-3101PC spectral photometer, and its polarizing spectrum was tested at the incident angles of 30 and 45 respectively. The experimental result indicates that such anodic alumina film with Co columns has good transmittance and extinction ratio in the near-infrared waveband, and the extinction ratio improves notably with increase of the incident angle.
2011, 35(6): 775-777.
doi: 10.3969/j.issn.1001-3806.2011.06.014
Abstract:
In order to analyze the effect of the misalignment of crystal optical axis on the performance of a Glan-Thompson prism, the beam deflection angle, the extinction ratio and the transmittance was discussed by theoretical calculation based on the birefringence of iceland spar crystals. The theoretical calculation formulas were given. It is concluded that the misalignment of optical axis of crystal has no effect on the extinction ratio, while the misalignment of transverse direction affects the transmittance to a certain extent, and the misalignment of longitudinal direction affects the beam deflection angle. For high-precision Glan-Thompson prism, the effect of misalignment of optical axis on extinction ratio and beam deflection angle must be avoided.
In order to analyze the effect of the misalignment of crystal optical axis on the performance of a Glan-Thompson prism, the beam deflection angle, the extinction ratio and the transmittance was discussed by theoretical calculation based on the birefringence of iceland spar crystals. The theoretical calculation formulas were given. It is concluded that the misalignment of optical axis of crystal has no effect on the extinction ratio, while the misalignment of transverse direction affects the transmittance to a certain extent, and the misalignment of longitudinal direction affects the beam deflection angle. For high-precision Glan-Thompson prism, the effect of misalignment of optical axis on extinction ratio and beam deflection angle must be avoided.
2011, 35(6): 778-780,853.
doi: 10.3969/j.issn.1001-3806.2011.06.015
Abstract:
In order to design a broadband distributed fiber Raman amplifier, after simulating the forward pumping mode Raman coupling equations, proper wavelengths were obtained, and it was found that the bandwidth was 80nm at 1530nm～1610nm for a distributed Raman fiber amplifier. Under the condition of uniform pump, after amplifying the signals in 80 signal channels, the signal and pump power along the fiber, the output power and gain of each channel were analyzed. The pumping power was adjusted to improve signal and gain flatness. After transmitting in a G655 single mode fiber in 50km long, the average gain was about 10dB, and the gain flatness was 1dB. This result plays important instructive role in the design of broadband distributed fiber Raman amplifiers.
In order to design a broadband distributed fiber Raman amplifier, after simulating the forward pumping mode Raman coupling equations, proper wavelengths were obtained, and it was found that the bandwidth was 80nm at 1530nm～1610nm for a distributed Raman fiber amplifier. Under the condition of uniform pump, after amplifying the signals in 80 signal channels, the signal and pump power along the fiber, the output power and gain of each channel were analyzed. The pumping power was adjusted to improve signal and gain flatness. After transmitting in a G655 single mode fiber in 50km long, the average gain was about 10dB, and the gain flatness was 1dB. This result plays important instructive role in the design of broadband distributed fiber Raman amplifiers.
2011, 35(6): 781-783,799.
doi: 10.3969/j.issn.1001-3806.2011.06.016
Abstract:
In order to study the effect of oxygen pressure on the structure and optical property of ZnO thin films, different Cu-doped ZnO thin films were prepared on P-Si〈111〉 substrates by means of pulsed laser deposition (PLD) technique. The structures of the specimens were analyzed with X-ray diffraction(XRD)and their photoluminescence spectra were measured with a fluorescent spectrophotometer. XRD patterns indicate all the specimens prepared under the conditions of 400℃ substrate temperature and 0.2Pa oxygen pressure have a strong diffraction peak and high preferential orientation in the (002) crystallographic direction，but the diffraction peak of Cu doesn't appear. Results at room temperature showed that each of the samples had a blue band at about 460nm (2.71eV).The blue emission is attributed to the transition of electrons from the bottom of conduction band to zinc vacancy or from zinc interstitial to the top of valence band. The photoluminescence intensity of the emission luminescence increases as the oxygen pressure increases.
In order to study the effect of oxygen pressure on the structure and optical property of ZnO thin films, different Cu-doped ZnO thin films were prepared on P-Si〈111〉 substrates by means of pulsed laser deposition (PLD) technique. The structures of the specimens were analyzed with X-ray diffraction(XRD)and their photoluminescence spectra were measured with a fluorescent spectrophotometer. XRD patterns indicate all the specimens prepared under the conditions of 400℃ substrate temperature and 0.2Pa oxygen pressure have a strong diffraction peak and high preferential orientation in the (002) crystallographic direction，but the diffraction peak of Cu doesn't appear. Results at room temperature showed that each of the samples had a blue band at about 460nm (2.71eV).The blue emission is attributed to the transition of electrons from the bottom of conduction band to zinc vacancy or from zinc interstitial to the top of valence band. The photoluminescence intensity of the emission luminescence increases as the oxygen pressure increases.
2011, 35(6): 784-786,836.
doi: 10.3969/j.issn.1001-3806.2011.06.017
Abstract:
In order to detect and evaluate the flatness of small plane of diffuse reflection, a method was presented based on carrier fringe phase analysis. With a laser as illuminating light source, a coherent fringe pattern at period of 100m was achieved. The modulated phase distribution of the testing surface was retrieved after Fourier transform and converted into the physical height distribution, and then these height data were applied to evaluate the surface flatness. The detailed theoretical analysis was presented. The theoretical height resolution can reach 10m. Due to the effect of the noise, the experimental height resolution only reached 20m. The experimental results prove that the method is valid.
In order to detect and evaluate the flatness of small plane of diffuse reflection, a method was presented based on carrier fringe phase analysis. With a laser as illuminating light source, a coherent fringe pattern at period of 100m was achieved. The modulated phase distribution of the testing surface was retrieved after Fourier transform and converted into the physical height distribution, and then these height data were applied to evaluate the surface flatness. The detailed theoretical analysis was presented. The theoretical height resolution can reach 10m. Due to the effect of the noise, the experimental height resolution only reached 20m. The experimental results prove that the method is valid.
2011, 35(6): 787-791.
doi: 10.3969/j.issn.1001-3806.2011.06.018
Abstract:
Based on the anisotropy semianalytical thermal analysis, the temperature field and thermal distortion of rectangle Nd:GGG crystal in a double side dislocation pumping laser was investigated. A maximum temperature rise of 309.73℃ happened on the front pumping face and the Gaussian radius w became 9.00mm with two 300W laser diode arrays side-pumping Nd:GGG laser crystal. After analyzing the working characteristics of the laser crystal, a thermal model that matches actual situation of the laser crystal was established, and the analytical expressions of the temperature field and thermal distortion field of the rectangle Nd:GGG laser crystal were obtained. With double side dislocation pumping the rectangle Nd:GGG crystal for 10s, there happened maximum thermal distortion of 28.97m and a maximum optical path difference of 13.02m. After stopping pumping for 200s, the maximum temperature rise dropped to 1.01%. These results provide theoretical basis for the optimized design of LD double side pumped heat capacity lasers.
Based on the anisotropy semianalytical thermal analysis, the temperature field and thermal distortion of rectangle Nd:GGG crystal in a double side dislocation pumping laser was investigated. A maximum temperature rise of 309.73℃ happened on the front pumping face and the Gaussian radius w became 9.00mm with two 300W laser diode arrays side-pumping Nd:GGG laser crystal. After analyzing the working characteristics of the laser crystal, a thermal model that matches actual situation of the laser crystal was established, and the analytical expressions of the temperature field and thermal distortion field of the rectangle Nd:GGG laser crystal were obtained. With double side dislocation pumping the rectangle Nd:GGG crystal for 10s, there happened maximum thermal distortion of 28.97m and a maximum optical path difference of 13.02m. After stopping pumping for 200s, the maximum temperature rise dropped to 1.01%. These results provide theoretical basis for the optimized design of LD double side pumped heat capacity lasers.
2011, 35(6): 792-794.
doi: 10.3969/j.issn.1001-3806.2011.06.019
Abstract:
In order to ensure the performance of a laser rangefinder, a new testing instrument was designed to detect its performance based on photoelectric coupling method. The position of emitting and receiving units can be adjusted and exchanged arbitrarily in the instrument. It has other advantages of convenience of aiming adjustment, digital display of test results. Test results show that this device can quickly test the performance of different laser rangefinders, improve the detection efficiency and testing precision.
In order to ensure the performance of a laser rangefinder, a new testing instrument was designed to detect its performance based on photoelectric coupling method. The position of emitting and receiving units can be adjusted and exchanged arbitrarily in the instrument. It has other advantages of convenience of aiming adjustment, digital display of test results. Test results show that this device can quickly test the performance of different laser rangefinders, improve the detection efficiency and testing precision.
2011, 35(6): 795-799.
doi: 10.3969/j.issn.1001-3806.2011.06.020
Abstract:
Airborne laser Doppler wind lidars and their applications were introduced. The basic working principle, system constitution, application modes and fields were analyzed. It was predicated that the fiber laser should be applied in airborne laser Doppler wind lidars for the wind lidars combined with all-fiber coherent laser have advantages of high accuracy, reliable measurement, fast response, and compact volume, etc. The airborne Doppler lidars can be used in many applications such as airdrop or flight safety for large airplanes since detailed meteorological parameters can be provided.
Airborne laser Doppler wind lidars and their applications were introduced. The basic working principle, system constitution, application modes and fields were analyzed. It was predicated that the fiber laser should be applied in airborne laser Doppler wind lidars for the wind lidars combined with all-fiber coherent laser have advantages of high accuracy, reliable measurement, fast response, and compact volume, etc. The airborne Doppler lidars can be used in many applications such as airdrop or flight safety for large airplanes since detailed meteorological parameters can be provided.
2011, 35(6): 800-803.
doi: 10.3969/j.issn.1001-3806.2011.06.021
Abstract:
In order to study the properties of laser-induced plasma at different ambient pressures, emission spectroscopy was studied on aluminum plasma generated by CO2 laser with energy of 180mJ/pulse at different air ambient pressures. The dependency of plasma temperature and density on ambient pressures were estimated from the analysis of spectral data by assuming the conditions of local thermodynamic equilibrium and optically thin plasma. Electron temperature was measured in the range of 1.05eV~2.47eV, and electron density was measured in the range of 1.95 1016cm-310.5 1016cm-3, as the ambient pressure was varied from 10-4Pa to 2 103Pa. The results show that the plasma temperature decreases with the ambient pressures. At first, the electron density decreases with the increase of ambient pressure under low pressure. When the pressure reaches 600Pa, the broken air plasma may interact with Al vapor and the electron density increases with the pressure increasing. For larger ambient pressure up to 3000Pa, the Al emission lines eventually disappear, suggesting that the laser energy is almost screened by the air plasma. The results provide useful guidance to understand the influence of air pressure on laser-matter interaction.
In order to study the properties of laser-induced plasma at different ambient pressures, emission spectroscopy was studied on aluminum plasma generated by CO2 laser with energy of 180mJ/pulse at different air ambient pressures. The dependency of plasma temperature and density on ambient pressures were estimated from the analysis of spectral data by assuming the conditions of local thermodynamic equilibrium and optically thin plasma. Electron temperature was measured in the range of 1.05eV~2.47eV, and electron density was measured in the range of 1.95 1016cm-310.5 1016cm-3, as the ambient pressure was varied from 10-4Pa to 2 103Pa. The results show that the plasma temperature decreases with the ambient pressures. At first, the electron density decreases with the increase of ambient pressure under low pressure. When the pressure reaches 600Pa, the broken air plasma may interact with Al vapor and the electron density increases with the pressure increasing. For larger ambient pressure up to 3000Pa, the Al emission lines eventually disappear, suggesting that the laser energy is almost screened by the air plasma. The results provide useful guidance to understand the influence of air pressure on laser-matter interaction.
2011, 35(6): 804-807.
doi: 10.3969/j.issn.1001-3806.2011.06.022
Abstract:
In order to obtain the real-time spectrum distribution information of such as chemical warfare, atmospheric pollutants by Fourier transform spectrometer, a data processing system, which can realize the single sideband interference fringes collection and spectrum recovery, was designed based on field pragrammable gate array(FPGA). In the system, apodization, fast Fourier transform(FFT), and phase correction was integrated in a FPGA chip with the advantages of high integration, high speed and low cost. The XC2VP30 chip of Xilinx's corporation was used to design the data processing module hardware circuit. Then the data collected by WQF-520 Fourier transform infrared spectrometer was transferred to FPGA for processing. Comparing the FPGA results with Matlab simulation results, the difference is within 1.2%. The results show that the system can recover spectrum correctly and is suitable for the interferometric spectrometer system of time modulation and space modulation.
In order to obtain the real-time spectrum distribution information of such as chemical warfare, atmospheric pollutants by Fourier transform spectrometer, a data processing system, which can realize the single sideband interference fringes collection and spectrum recovery, was designed based on field pragrammable gate array(FPGA). In the system, apodization, fast Fourier transform(FFT), and phase correction was integrated in a FPGA chip with the advantages of high integration, high speed and low cost. The XC2VP30 chip of Xilinx's corporation was used to design the data processing module hardware circuit. Then the data collected by WQF-520 Fourier transform infrared spectrometer was transferred to FPGA for processing. Comparing the FPGA results with Matlab simulation results, the difference is within 1.2%. The results show that the system can recover spectrum correctly and is suitable for the interferometric spectrometer system of time modulation and space modulation.
2011, 35(6): 808-812,816.
doi: 10.3969/j.issn.1001-3806.2011.06.023
Abstract:
Brillouin light detection and ranging(LIDAR)in ocean telemetry is a novel frequency detection LIDAR technology, involves Brillouin scattering, LIDAR and remote sensing technology. For this detection mode can resist amplitude noise, so it has high signal-to-noise ratio, strong anti-interference and high accuracy of measurement. Firstly, key technologies of Brillouin LIDAR were analyzed，and the development progress was introduced. Finally, a few of applications of Brillouin LIDAR in ocean telemetry and the development trend were discussed.
Brillouin light detection and ranging(LIDAR)in ocean telemetry is a novel frequency detection LIDAR technology, involves Brillouin scattering, LIDAR and remote sensing technology. For this detection mode can resist amplitude noise, so it has high signal-to-noise ratio, strong anti-interference and high accuracy of measurement. Firstly, key technologies of Brillouin LIDAR were analyzed，and the development progress was introduced. Finally, a few of applications of Brillouin LIDAR in ocean telemetry and the development trend were discussed.
2011, 35(6): 813-816.
doi: 10.3969/j.issn.1001-3806.2011.06.024
Abstract:
In order to obtain the modulation instability of 1-D broad optical beams in biased two-photon centrosymmetric photorefractive crystals under steady-state conditions, the growth rate of 1-D modulation instability was obtained by means of numerical simulation method after treating the space-charge field locally. The numerical results show that the maximum modulation instability growth rates increases linearly with the external electric field and spatial-frequency when the incident optical intensity is constant. When the external electric field is fixed, the maximum modulation instability growth rates increases to a maximum then decreases as the incident optical intensity increases. The modulation instability of 1-D broad optical beams depends on the external bias field and the ratio of optical beam's intensity to that of the dark irradiance.
In order to obtain the modulation instability of 1-D broad optical beams in biased two-photon centrosymmetric photorefractive crystals under steady-state conditions, the growth rate of 1-D modulation instability was obtained by means of numerical simulation method after treating the space-charge field locally. The numerical results show that the maximum modulation instability growth rates increases linearly with the external electric field and spatial-frequency when the incident optical intensity is constant. When the external electric field is fixed, the maximum modulation instability growth rates increases to a maximum then decreases as the incident optical intensity increases. The modulation instability of 1-D broad optical beams depends on the external bias field and the ratio of optical beam's intensity to that of the dark irradiance.
2011, 35(6): 817-819.
doi: 10.3969/j.issn.1001-3806.2011.06.025
Abstract:
In order to find out the influence of the percentage of doping concentration of core surround on transmission characteristics in photonic band gap photonic crystal fibers(PBG-PCF), simulations on 7-cell PBG-PCF core surround doping and 19-cell PBG-PCF core surround doping were carried out by using full-vector finite element method under the condition of the percentage of doping concentration between 1% and 5%. The core-confined energy of these two structures were compared, and the influence of the percentage of doping concentration on optical fiber transmission characteristics in 19-cell PBG-PCF was investigated, such as the distribution curves of bandwidth, dispersion, effective mode area and effective mode index in different the percentage of doping concentration. The results show that the light limiting capacity of 19-cell PBG-PCF is better than that of 7-cell PBG-PCF, and the percentage of doping concentration has notable influence on optical fiber transmission characteristics.
In order to find out the influence of the percentage of doping concentration of core surround on transmission characteristics in photonic band gap photonic crystal fibers(PBG-PCF), simulations on 7-cell PBG-PCF core surround doping and 19-cell PBG-PCF core surround doping were carried out by using full-vector finite element method under the condition of the percentage of doping concentration between 1% and 5%. The core-confined energy of these two structures were compared, and the influence of the percentage of doping concentration on optical fiber transmission characteristics in 19-cell PBG-PCF was investigated, such as the distribution curves of bandwidth, dispersion, effective mode area and effective mode index in different the percentage of doping concentration. The results show that the light limiting capacity of 19-cell PBG-PCF is better than that of 7-cell PBG-PCF, and the percentage of doping concentration has notable influence on optical fiber transmission characteristics.
2011, 35(6): 820-823,827.
doi: 10.3969/j.issn.1001-3806.2011.06.026
Abstract:
In order to study the fabricating process and the theory of the micro opto-electronic mechanical system(MOEMS)corner-cube reflector(CCR), the self-assembly method was used. The principle of self-assembly method fabricating MOEMS CCR was introduced. First, the shape of hinge can be patterned by lithography and the region of CCR plane was selectively etched. Secondly, using selective etching solutions, the sacrificial layer was exposed. Thirdly, after the sacrificial layer was etched, the CCR was self-assembled through the hinge drive the mirror bending up under the driven stress until reach an equilibrium position, which the driven stress was created by the lattice mismatch between the bilayer. Because finite element method was suitable to solve the nonlinear problems of elastic stress, it was applied to analysis and models the CCR, mirrors with different angels and a micro-cube box were also successfully simulated. Furthermore, by adjusting the size of mirror and hinge, the thickness of the strain bilayer and the top layer, which affect the rotation angle of the mirror, simulation analysis was carried out. It was shown that the self-assembly method was one of very feasible method for fabricating 3-D micro/nano structures and had a good prospect of application.
In order to study the fabricating process and the theory of the micro opto-electronic mechanical system(MOEMS)corner-cube reflector(CCR), the self-assembly method was used. The principle of self-assembly method fabricating MOEMS CCR was introduced. First, the shape of hinge can be patterned by lithography and the region of CCR plane was selectively etched. Secondly, using selective etching solutions, the sacrificial layer was exposed. Thirdly, after the sacrificial layer was etched, the CCR was self-assembled through the hinge drive the mirror bending up under the driven stress until reach an equilibrium position, which the driven stress was created by the lattice mismatch between the bilayer. Because finite element method was suitable to solve the nonlinear problems of elastic stress, it was applied to analysis and models the CCR, mirrors with different angels and a micro-cube box were also successfully simulated. Furthermore, by adjusting the size of mirror and hinge, the thickness of the strain bilayer and the top layer, which affect the rotation angle of the mirror, simulation analysis was carried out. It was shown that the self-assembly method was one of very feasible method for fabricating 3-D micro/nano structures and had a good prospect of application.
2011, 35(6): 824-827.
doi: 10.3969/j.issn.1001-3806.2011.06.027
Abstract:
In order to adopt lens ducts in a coupling system for laser diode array(LDA), the function of the coupling efficiency with the parameters of the lens duct, such as the radius of curvature, the length of the lens duct, the side length of the output face and the fast axis divergence angle was obtained based on mirror-image method. The coupling efficiency of different size of LDA coupling into the laser rod was analyzed. The results are important in designing lens duct for LDA.
In order to adopt lens ducts in a coupling system for laser diode array(LDA), the function of the coupling efficiency with the parameters of the lens duct, such as the radius of curvature, the length of the lens duct, the side length of the output face and the fast axis divergence angle was obtained based on mirror-image method. The coupling efficiency of different size of LDA coupling into the laser rod was analyzed. The results are important in designing lens duct for LDA.
2011, 35(6): 828-832.
doi: 10.3969/j.issn.1001-3806.2011.06.028
Abstract:
In order to analyze the link performance of ultraviolet(UV)non line-of-sight(NLOS)communication network, based on the atmospheric single-scattered transmission model for the UV NLOS communication, two types of UV NLOS communication, i.e., all-direction transmitting and receiving, directed transmission and omni-direction receiving, were simulated in the chain and mesh topologies respectively. Then the network performance such as throughput, end-to-end delay, jitter etc were compared and analyzed through computer simulation. The results show that the performance of directed transmission and omni-direction receiving is more superior in the ultraviolet wireless optical network.
In order to analyze the link performance of ultraviolet(UV)non line-of-sight(NLOS)communication network, based on the atmospheric single-scattered transmission model for the UV NLOS communication, two types of UV NLOS communication, i.e., all-direction transmitting and receiving, directed transmission and omni-direction receiving, were simulated in the chain and mesh topologies respectively. Then the network performance such as throughput, end-to-end delay, jitter etc were compared and analyzed through computer simulation. The results show that the performance of directed transmission and omni-direction receiving is more superior in the ultraviolet wireless optical network.
2011, 35(6): 833-836.
doi: 10.3969/j.issn.1001-3806.2011.06.029
Abstract:
In order to know the effect of a Wollaston prism on o beam and e beam when it is applied to divergent beam, the splitting angles of o light and e light were respectively deduced according to refraction law when both edge rays of the divergent beam incident on a Wollaston prism. The variation of emergent o beam and e beam was analyzed with the method of controlling variables as divergent beam passing through a Wollaston prism, and the effect of a Wollaston prism on the divergent angle of obeam and e beam was obtained. The result show the divergent angle of o beam becomes larger than that of the incident beam and the divergent angle of e beam becomes larger; For a prism with given structure angles, the divergent angle of o beam increases when the wavelength of incident light increases, but the divergent angle of e beam decreases. For a certain monochromatic divergent beam, the divergent angle of o beam increases with the decrease of structure angle, while e beam increased with it. Both of the changes of incident light's wavelength and prism's structure angle have limit effect on the divergent angles of o beam and e beam. The effect of a Wollaston prism on the divergent angles of o beam and e beam can be neglected in the application with lower precision requirements.
In order to know the effect of a Wollaston prism on o beam and e beam when it is applied to divergent beam, the splitting angles of o light and e light were respectively deduced according to refraction law when both edge rays of the divergent beam incident on a Wollaston prism. The variation of emergent o beam and e beam was analyzed with the method of controlling variables as divergent beam passing through a Wollaston prism, and the effect of a Wollaston prism on the divergent angle of obeam and e beam was obtained. The result show the divergent angle of o beam becomes larger than that of the incident beam and the divergent angle of e beam becomes larger; For a prism with given structure angles, the divergent angle of o beam increases when the wavelength of incident light increases, but the divergent angle of e beam decreases. For a certain monochromatic divergent beam, the divergent angle of o beam increases with the decrease of structure angle, while e beam increased with it. Both of the changes of incident light's wavelength and prism's structure angle have limit effect on the divergent angles of o beam and e beam. The effect of a Wollaston prism on the divergent angles of o beam and e beam can be neglected in the application with lower precision requirements.
2011, 35(6): 837-840,856.
doi: 10.3969/j.issn.1001-3806.2011.06.030
Abstract:
To study the microphysical characteristics of clouds and precipitation, theoretical boundary diffraction field was derived according to Young's boundary diffraction theory and diffraction field distributions were established under exposure of point light source on the optical axis and parallel monochromatic light with the Fraunhofer approximation, the boundary diffraction field of droplet under exposure of monochromatic parallel light was simulated with MATHEMATICA and MATLAB. Furthermore, the effect of boundary diffraction on droplet detection was analyzed and accordingly a threshold change solution was put forward. It is concluded that diffraction by an aperture is addition of geometric projection and boundary diffraction, boundary diffraction is caused by non-uniformity of particles'edge, varying with size and shape. It is meaningful for the detection of droplets.
To study the microphysical characteristics of clouds and precipitation, theoretical boundary diffraction field was derived according to Young's boundary diffraction theory and diffraction field distributions were established under exposure of point light source on the optical axis and parallel monochromatic light with the Fraunhofer approximation, the boundary diffraction field of droplet under exposure of monochromatic parallel light was simulated with MATHEMATICA and MATLAB. Furthermore, the effect of boundary diffraction on droplet detection was analyzed and accordingly a threshold change solution was put forward. It is concluded that diffraction by an aperture is addition of geometric projection and boundary diffraction, boundary diffraction is caused by non-uniformity of particles'edge, varying with size and shape. It is meaningful for the detection of droplets.
2011, 35(6): 841-843,848.
doi: 10.3969/j.issn.1001-3806.2011.06.031
Abstract:
In order to solve real-time reconstruction of digital hologram and CCD acquisition problems, a software was developed based on the technology of component object model(COM)to combine the user-friendly feature of VB and the powerful computing capabilities of MATLAB perfectly. Experimental results show the high reliability and feasibility of the software. It will give a great help to the research in digital holographic.
In order to solve real-time reconstruction of digital hologram and CCD acquisition problems, a software was developed based on the technology of component object model(COM)to combine the user-friendly feature of VB and the powerful computing capabilities of MATLAB perfectly. Experimental results show the high reliability and feasibility of the software. It will give a great help to the research in digital holographic.
2011, 35(6): 844-848.
doi: 10.3969/j.issn.1001-3806.2011.06.032
Abstract:
During the process of laser de-icing applied in the electric grid, the electrical equipment such as insulator should not be damaged by the laser. The temperature and stress field distributions of normal porcelain, alumina porcelain, zirconium oxide porcelain and cordierite porcelain after laser irradiating are obtained by using ANSYS software. The results show that alumina porcelain has advantages in characteristics of anti-damage of thermal induced stress. The experiments of surface damage of insulator with Nd:YAG laser irradiation are explored. The relations between surface temperature and irradiating time are obtained. So is the damage form. Numerical analysis and experiment results are both show that laser power density and irradiating time are considered as the important influence factors of laser damage of the insulator. Thermal damage and thermal-stress damage are the main types of laser damage of porcelain insulator, which are related to the surface temperature after laser irradiation. The anti-damage methods of aiming and controlling, combining laser de-icing with other de-icing methods to protect the insulator are also proposed.
During the process of laser de-icing applied in the electric grid, the electrical equipment such as insulator should not be damaged by the laser. The temperature and stress field distributions of normal porcelain, alumina porcelain, zirconium oxide porcelain and cordierite porcelain after laser irradiating are obtained by using ANSYS software. The results show that alumina porcelain has advantages in characteristics of anti-damage of thermal induced stress. The experiments of surface damage of insulator with Nd:YAG laser irradiation are explored. The relations between surface temperature and irradiating time are obtained. So is the damage form. Numerical analysis and experiment results are both show that laser power density and irradiating time are considered as the important influence factors of laser damage of the insulator. Thermal damage and thermal-stress damage are the main types of laser damage of porcelain insulator, which are related to the surface temperature after laser irradiation. The anti-damage methods of aiming and controlling, combining laser de-icing with other de-icing methods to protect the insulator are also proposed.
2011, 35(6): 849-853.
doi: 10.3969/j.issn.1001-3806.2011.06.033
Abstract:
In order to study propagation characteristics of elegant Laguerre-Gaussian beam(ELGB) passing through a circular aperture in turbulent atmosphere, corresponding analytical formulate based on the extend Huygens-Fresnel integral were deduced and numerical simulation results were obtained. The results indicate that when the value of the truncation parameter 1, the beam profile of ELGB after propagating long distance is similar to that of the source, i.e., hallow beam, but the central normalized intensity is larger than 0; however, the profile tends to Gaussian distribution as the parameter 1. Meanwhile, the weaker the turbulent atmosphere is, the more easily it can preserve the average intensity profile as the source. And the average intensity profiles of different beam orders were also studied. The results are useful to laser beam propagation and free-space laser communication.
In order to study propagation characteristics of elegant Laguerre-Gaussian beam(ELGB) passing through a circular aperture in turbulent atmosphere, corresponding analytical formulate based on the extend Huygens-Fresnel integral were deduced and numerical simulation results were obtained. The results indicate that when the value of the truncation parameter 1, the beam profile of ELGB after propagating long distance is similar to that of the source, i.e., hallow beam, but the central normalized intensity is larger than 0; however, the profile tends to Gaussian distribution as the parameter 1. Meanwhile, the weaker the turbulent atmosphere is, the more easily it can preserve the average intensity profile as the source. And the average intensity profiles of different beam orders were also studied. The results are useful to laser beam propagation and free-space laser communication.
2011, 35(6): 854-856.
doi: 10.3969/j.issn.1001-3806.2011.06.034
Abstract:
In order to study the kinetic energy of the accelerated positrons in the wakefield of different laser pulses, by means of numerical simulation, the kinetic energy was obtained in the wakefiled of sine, flat-top and Gaussian asymmetric laser pulses. Simulation results show the energy driven by asymmetric sine pulses is higher than those driven by flat-top and Gaussian laser pulses.
In order to study the kinetic energy of the accelerated positrons in the wakefield of different laser pulses, by means of numerical simulation, the kinetic energy was obtained in the wakefiled of sine, flat-top and Gaussian asymmetric laser pulses. Simulation results show the energy driven by asymmetric sine pulses is higher than those driven by flat-top and Gaussian laser pulses.
2011, 35(6): 857-860,864.
doi: 10.3969/j.issn.1001-3806.2011.06.03
Abstract:
For solving the problem of non-uniformity of light emitting diode(LED) illumination, based on basic principles of non-imaging optics and geometric optics, the design procedure of a LED reflecting secondary optical system was deduced. Then a LED reflecting secondary optical system was designed and its illumination uniformity was simulated. Aiming at the problem reflected by the simulation result, the designing procedure was improved. Then the secondary optical system was redesigned, the result of simulation shows this optical system can achieve the illumination uniformity.
For solving the problem of non-uniformity of light emitting diode(LED) illumination, based on basic principles of non-imaging optics and geometric optics, the design procedure of a LED reflecting secondary optical system was deduced. Then a LED reflecting secondary optical system was designed and its illumination uniformity was simulated. Aiming at the problem reflected by the simulation result, the designing procedure was improved. Then the secondary optical system was redesigned, the result of simulation shows this optical system can achieve the illumination uniformity.
2011, 35(6): 861-864.
doi: 10.3969/j.issn.1001-3806.2011.06.036
Abstract:
Starting from the Collins diffraction integral formula, the propagation formula of flattened Gaussian beam passing through a beam expander was derived. Taking both Galileo and Kepler beam expander systems as examples, the intensity distribution was simulated. The numerical calculation shows that the propagation properties are different between the Galileo and Kepler beam expander systems with the same amplification as well as different focus length of the lens. What is more, the flat-topped beam is also obtained during certain axial displacement as well as the image plane of the Kepler beam expander, and the axial displacement is increased with the increase of the expander amplification.
Starting from the Collins diffraction integral formula, the propagation formula of flattened Gaussian beam passing through a beam expander was derived. Taking both Galileo and Kepler beam expander systems as examples, the intensity distribution was simulated. The numerical calculation shows that the propagation properties are different between the Galileo and Kepler beam expander systems with the same amplification as well as different focus length of the lens. What is more, the flat-topped beam is also obtained during certain axial displacement as well as the image plane of the Kepler beam expander, and the axial displacement is increased with the increase of the expander amplification.
