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RSS2010 Vol. 34, No. 4
Display Method:
Research of the fabrication of micro channels in a fused silica substrate using laser-induced plasma
2010, 34(4): 433-435,451.
doi: 10.3969/j.issn.1001-3806.2010.04.001
[Abstract]
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Abstract:
In order to fabricate high-quality micro channels in a fused silica,the fundamental frequency laser of a Qswitched Nd:YAG laser at 1064nm and the mixing laser composed of 70% second harmonic laser and 30% fundamental frequency laser were used to irradiate a fused silica substrate respectively to induce the plasma,by which micro channels in a fused silica substrate were fabricated.And the reasons for difference between two kinds of processing methods were analyzed.The results show that the interior wall of the channels processed by mixing laser are smoother and its drilling rate is faster than that processed by fundamental frequency.Furthermore,the depth of the channels processed by the mixing laser is up to 8mm.
In order to fabricate high-quality micro channels in a fused silica,the fundamental frequency laser of a Qswitched Nd:YAG laser at 1064nm and the mixing laser composed of 70% second harmonic laser and 30% fundamental frequency laser were used to irradiate a fused silica substrate respectively to induce the plasma,by which micro channels in a fused silica substrate were fabricated.And the reasons for difference between two kinds of processing methods were analyzed.The results show that the interior wall of the channels processed by mixing laser are smoother and its drilling rate is faster than that processed by fundamental frequency.Furthermore,the depth of the channels processed by the mixing laser is up to 8mm.
2010, 34(4): 436-439.
doi: 10.3969/j.issn.1001-3806.2010.04.002
Abstract:
A photoelectric detection method based on black-white bar code and modern photoelectric detection technology was selected for measuring the displacement deviation of printing press cylinder surface in high-speed motion state.A highprecision non-contact photoelectric detection system was designed and implemented.The accurate testing barcode was used to verify work status and measurement accuracy of the system in high-speed measurement state for assessing the quality of the system,low measurement error less than±3μm.The given experiment results indicate that:the system has stable working condition,high measurement speed,meeting the accuracy requirements of measuring the overprint deviation,and giving a new technological means to effectively solving overprint deviation.
A photoelectric detection method based on black-white bar code and modern photoelectric detection technology was selected for measuring the displacement deviation of printing press cylinder surface in high-speed motion state.A highprecision non-contact photoelectric detection system was designed and implemented.The accurate testing barcode was used to verify work status and measurement accuracy of the system in high-speed measurement state for assessing the quality of the system,low measurement error less than±3μm.The given experiment results indicate that:the system has stable working condition,high measurement speed,meeting the accuracy requirements of measuring the overprint deviation,and giving a new technological means to effectively solving overprint deviation.
2010, 34(4): 440-442,455.
doi: 10.3969/j.issn.1001-3806.2010.04.003
Abstract:
To exam the chaotic dynamics of multiple modulated delays system,the synchronization in multiple constant and modulated time delay chaotic lasers subject to incoherent optical feedbacks and incoherent optical injection is numerically investigated,in which the semiconductor lasers are subject to incoherent injection that fine tuning of optical frequency is not required.Furthermore,the autocorrelation function of the incoherent feedback semiconductor laser output is also investigated.The results indicate that high quality of synchronization can be obtained under both the cases.However,the signatures of time delays under modulated delays case can be hidden,which largely improves the system security and is important for the suitability of such laser systems for secure chaos-based communication systems.
To exam the chaotic dynamics of multiple modulated delays system,the synchronization in multiple constant and modulated time delay chaotic lasers subject to incoherent optical feedbacks and incoherent optical injection is numerically investigated,in which the semiconductor lasers are subject to incoherent injection that fine tuning of optical frequency is not required.Furthermore,the autocorrelation function of the incoherent feedback semiconductor laser output is also investigated.The results indicate that high quality of synchronization can be obtained under both the cases.However,the signatures of time delays under modulated delays case can be hidden,which largely improves the system security and is important for the suitability of such laser systems for secure chaos-based communication systems.
2010, 34(4): 443-446.
doi: 10.3969/j.issn.1001-3806.2010.04.004
Abstract:
In order to study the relationship between process parameters and densification of melted parts formed by selective laser melting,several specimens were formed by scanning strategy with adjacent layers staggered and different scanning space,scanning speed and laser power in independently developed selective laser melting equipment DiMetal-280,using 316L stainless steel powder.Microscope was employed to observe and analyze the surface morphologies of specimens and the densification was measured with water-draining method.Results showed that densification increased when scanning strategy with adjacent layers staggered was employed under reasonable process parameters,however,decreased with increasing of scanning space due to the changes of track overlapping and also decreased when scanning speed was too low or too high or when practical thickness of powder changed in the beginning of process.The density of 316L stainless steel part formed by selective laser melting can be further improved based on the research.
In order to study the relationship between process parameters and densification of melted parts formed by selective laser melting,several specimens were formed by scanning strategy with adjacent layers staggered and different scanning space,scanning speed and laser power in independently developed selective laser melting equipment DiMetal-280,using 316L stainless steel powder.Microscope was employed to observe and analyze the surface morphologies of specimens and the densification was measured with water-draining method.Results showed that densification increased when scanning strategy with adjacent layers staggered was employed under reasonable process parameters,however,decreased with increasing of scanning space due to the changes of track overlapping and also decreased when scanning speed was too low or too high or when practical thickness of powder changed in the beginning of process.The density of 316L stainless steel part formed by selective laser melting can be further improved based on the research.
2010, 34(4): 447-451.
doi: 10.3969/j.issn.1001-3806.2010.04.005
Abstract:
In order to manufacture high density parts with high quality surface by means of selective laser melting technique,orthogonal test method was applied to investigate fiber laser selective laser melting of 316L stainless steel powder.Defects among scan lines and protuberance of outside frame of samples were found in the experiments,which were great impediments for part quality improvement.Then,"inter-layer stagger" scan strategy was applied for its better wetting ability and fabrication efficiency.Bonding quality among scan lines and layers was analyzed by means of micro-observing and fewer holes were found and better metallurgical bonding and higher density were achieved.Finally,optimized process parameters and "interlayer stagger" scan strategy were applied to manufacture customized orthopedics model,its micro-hardness and relative density were HV0.3 250 and 95.8% respectively.Results show that inter-layer scan strategy has fine effect on the quality of direct fabrication metal parts in selective laser melting process.
In order to manufacture high density parts with high quality surface by means of selective laser melting technique,orthogonal test method was applied to investigate fiber laser selective laser melting of 316L stainless steel powder.Defects among scan lines and protuberance of outside frame of samples were found in the experiments,which were great impediments for part quality improvement.Then,"inter-layer stagger" scan strategy was applied for its better wetting ability and fabrication efficiency.Bonding quality among scan lines and layers was analyzed by means of micro-observing and fewer holes were found and better metallurgical bonding and higher density were achieved.Finally,optimized process parameters and "interlayer stagger" scan strategy were applied to manufacture customized orthopedics model,its micro-hardness and relative density were HV0.3 250 and 95.8% respectively.Results show that inter-layer scan strategy has fine effect on the quality of direct fabrication metal parts in selective laser melting process.
2010, 34(4): 452-455.
doi: 10.3969/j.issn.1001-3806.2010.04.006
Abstract:
In order to obtain low-amplitude two-photon screening-photovohaic spatial solitons,low-amplitude spatial solitons in biased two-photon photovohaie photorefractive crystals were studied.Then,the analytical expressions for both the bright and dark low-amplitude two-photon sereening-photovoltaic spatial solitons in photorefractive crystals were obtained.The explicit expressions for the width of these spatial solitons were deduced.The result shows that the low-amplitude two-photon screeningphotovoltaic solitons can be considered as the united form of screening solitons and photovohaic solitons.They reduce to screening soliton in the absence of photovoltaic effect,whereas they become photovoltaie solitons under the open or closed circuit condition when the bias field is not applied.It turned out that this research provides theoretic basis for development of the spatial solitons theory.
In order to obtain low-amplitude two-photon screening-photovohaic spatial solitons,low-amplitude spatial solitons in biased two-photon photovohaie photorefractive crystals were studied.Then,the analytical expressions for both the bright and dark low-amplitude two-photon sereening-photovoltaic spatial solitons in photorefractive crystals were obtained.The explicit expressions for the width of these spatial solitons were deduced.The result shows that the low-amplitude two-photon screeningphotovoltaic solitons can be considered as the united form of screening solitons and photovohaic solitons.They reduce to screening soliton in the absence of photovoltaic effect,whereas they become photovoltaie solitons under the open or closed circuit condition when the bias field is not applied.It turned out that this research provides theoretic basis for development of the spatial solitons theory.
2010, 34(4): 456-458,528.
doi: 10.3969/j.issn.1001-3806.2010.04.007
Abstract:
In order to prepare good crystalline quality of Cu-doped ZnO thin films and study its structure,the film was prepared by means of the pulsed laser deposition method with the Si substrate at different temperatures.In experiments a better crystal quality of Cu-doped ZnO thin film was prepared successfully.The specimens were measured and analyzed by means of Xray diffraction,scanning electron microscopy and photoluminescence spectrum.It was found that the prepared specimens appeared highly c-axis oriented,and the surface morphology of thin film was uniform and dense with the substrate at 300℃.In their photoIuminescence spectrums,besides the peak UV luminescence around 380nm,there was a peak blue light-emitting band around 460nm,which made it possible to emit blue light with ZnO films in practice.The results show that the crystal quality is seriously dependent on the growth temperature.
In order to prepare good crystalline quality of Cu-doped ZnO thin films and study its structure,the film was prepared by means of the pulsed laser deposition method with the Si substrate at different temperatures.In experiments a better crystal quality of Cu-doped ZnO thin film was prepared successfully.The specimens were measured and analyzed by means of Xray diffraction,scanning electron microscopy and photoluminescence spectrum.It was found that the prepared specimens appeared highly c-axis oriented,and the surface morphology of thin film was uniform and dense with the substrate at 300℃.In their photoIuminescence spectrums,besides the peak UV luminescence around 380nm,there was a peak blue light-emitting band around 460nm,which made it possible to emit blue light with ZnO films in practice.The results show that the crystal quality is seriously dependent on the growth temperature.
2010, 34(4): 459-462,469.
doi: 10.3969/j.issn.1001-3806.2010.04.008
Abstract:
In order to study the weldability of magnesium alloy AZ91,1.5mm thick AZ91 magnesium alloy was welded with YAG pulsed laser through the art and craft of one side welding with back formation.Analysis showed that the organization of the joint were mainly fine equiaxed grains,with clear fusion line,no significant heat-affected zone and fewer defects.The grain size of the joints was significantly smaller than the base material's.And because of a large number of Mg evaporation which eventually leads to a corresponding increase of Al and Zn in the welding zone,the micro-hardness of the joint was higher than that of the base material.The results show that AZ91 magnesium alloy has good weldability for YAG pulsed laser based on reasonable technological measures.
In order to study the weldability of magnesium alloy AZ91,1.5mm thick AZ91 magnesium alloy was welded with YAG pulsed laser through the art and craft of one side welding with back formation.Analysis showed that the organization of the joint were mainly fine equiaxed grains,with clear fusion line,no significant heat-affected zone and fewer defects.The grain size of the joints was significantly smaller than the base material's.And because of a large number of Mg evaporation which eventually leads to a corresponding increase of Al and Zn in the welding zone,the micro-hardness of the joint was higher than that of the base material.The results show that AZ91 magnesium alloy has good weldability for YAG pulsed laser based on reasonable technological measures.
2010, 34(4): 463-465,481.
doi: 10.3969/j.issn.1001-3806.2010.04.009
Abstract:
To improve the durable hydrophobicity of sol-gel silica antireflective coating,methyl-modified silica sol was prepared through hydrolysis and condensation of tetraethoxysilane and methyhriethoxysilane under ammonia catalysis in ethanol solvent.Then the sol was dip-coated onto both sides of clean K9 glass substrate to form single layer coatings.The chemistry of coating was analyzed by FF-IR spectroscopy,the water contact angle of coating was measured by contact measurement,the transmittance of coating was measured by spectrophotometer,and the thickness and refractive index of coating were measured by spectroscopic ellipsometry.More importantly,the durability of hyddropobicity of hydrophobic coating was reported for the first time.The results showed that coatings gained water repellence and antireflectivity at the same time by introducing CH3 into Si-O-Si linkage.The peak transmittance of the coating was above 99.5%; the static water contact angle was 130°,and the hydropobicity of such coating could last for 5 months in environment with relative humidity of 90%.
To improve the durable hydrophobicity of sol-gel silica antireflective coating,methyl-modified silica sol was prepared through hydrolysis and condensation of tetraethoxysilane and methyhriethoxysilane under ammonia catalysis in ethanol solvent.Then the sol was dip-coated onto both sides of clean K9 glass substrate to form single layer coatings.The chemistry of coating was analyzed by FF-IR spectroscopy,the water contact angle of coating was measured by contact measurement,the transmittance of coating was measured by spectrophotometer,and the thickness and refractive index of coating were measured by spectroscopic ellipsometry.More importantly,the durability of hyddropobicity of hydrophobic coating was reported for the first time.The results showed that coatings gained water repellence and antireflectivity at the same time by introducing CH3 into Si-O-Si linkage.The peak transmittance of the coating was above 99.5%; the static water contact angle was 130°,and the hydropobicity of such coating could last for 5 months in environment with relative humidity of 90%.
2010, 34(4): 466-469.
doi: 10.3969/j.issn.1001-3806.2010.04.010
Abstract:
It takes advantages of free space optical communication (FSO) to transmit RF signal,which is proved to have special predominance.In order to research radio over free space optics technology,under the background of FSO,the simulation was adopted to study coding and decoding system based on the theory of 4 frequency-shift keying modulation and demodulation.The error rate and channel capacity after the RF signal passing Gaussian noise and Rayleigh channel were also analyzed.The simulation results on bit error rate(BER) of two demodulation methods show that the zero crossing detection system has the better BER than the coherent demodulation system when the signal-to-noise ratio is 12dB.
It takes advantages of free space optical communication (FSO) to transmit RF signal,which is proved to have special predominance.In order to research radio over free space optics technology,under the background of FSO,the simulation was adopted to study coding and decoding system based on the theory of 4 frequency-shift keying modulation and demodulation.The error rate and channel capacity after the RF signal passing Gaussian noise and Rayleigh channel were also analyzed.The simulation results on bit error rate(BER) of two demodulation methods show that the zero crossing detection system has the better BER than the coherent demodulation system when the signal-to-noise ratio is 12dB.
2010, 34(4): 470-474.
doi: 10.3969/j.issn.1001-3806.2010.04.011
Abstract:
In order to study the influence of system jitter on far field of coherently combined beams propagating in turbulent atmosphere,the expression for the far field energy distribution,affected by jitter of the system,was deduced based on Huygens-Fresnel principle.Taking a hexagonal-shaped laser array as an example,the influence of jitter on far-field was also analyzed with different turbulent intensity or transmission distance.The restricted phase jitter was depicted under the condition that the maximum intensity and power in the bucket were greater than ninety-two percent of the ideal ones.It is found the maximum intensity and power in the bucket are reduced due to jitter of the system.If the scope of jitter is definite,the effect of jitter will become worse with the decrease of the turbulent intensity or transmission distance.The results are helpful to research of coherent combination propagation in turbulent atmosphere.
In order to study the influence of system jitter on far field of coherently combined beams propagating in turbulent atmosphere,the expression for the far field energy distribution,affected by jitter of the system,was deduced based on Huygens-Fresnel principle.Taking a hexagonal-shaped laser array as an example,the influence of jitter on far-field was also analyzed with different turbulent intensity or transmission distance.The restricted phase jitter was depicted under the condition that the maximum intensity and power in the bucket were greater than ninety-two percent of the ideal ones.It is found the maximum intensity and power in the bucket are reduced due to jitter of the system.If the scope of jitter is definite,the effect of jitter will become worse with the decrease of the turbulent intensity or transmission distance.The results are helpful to research of coherent combination propagation in turbulent atmosphere.
2010, 34(4): 475-477,505.
doi: 10.3969/j.issn.1001-3806.2010.04.012
Abstract:
In order to analyze the influence of phase random fluctuation on the far field of coherent combined beams,the theoretical ways of Fourier optics method and ergodic hypothesis were employed to study the fringe contrast.The analytic expression of the fringe contrast ratio of coherent combined beam was deduced and the influence of random fluctuation of field phases on the contrast ratio of the far field pattern was numerically simulated successfully.Results show that with the quantity η increasing,the contrast ratio of coherent combined beams increase accordingly.The fringe contrast ratio of the far field pattern decreases when the root mean square of phase δφ enhances.For a fixed standard deviation of the phase's fluctuation and the quantity η,the larger the number of the constituent fields is,the bigger the fringe contrast ratio is.These results are useful for understanding of the characteristic of coherent combined beams.
In order to analyze the influence of phase random fluctuation on the far field of coherent combined beams,the theoretical ways of Fourier optics method and ergodic hypothesis were employed to study the fringe contrast.The analytic expression of the fringe contrast ratio of coherent combined beam was deduced and the influence of random fluctuation of field phases on the contrast ratio of the far field pattern was numerically simulated successfully.Results show that with the quantity η increasing,the contrast ratio of coherent combined beams increase accordingly.The fringe contrast ratio of the far field pattern decreases when the root mean square of phase δφ enhances.For a fixed standard deviation of the phase's fluctuation and the quantity η,the larger the number of the constituent fields is,the bigger the fringe contrast ratio is.These results are useful for understanding of the characteristic of coherent combined beams.
2010, 34(4): 478-481.
doi: 10.3969/j.issn.1001-3806.2010.04.013
Abstract:
In order to study effect of atmospheric channel on the beam quality under special circumstances,an indoor experiment system was built to simulate the situation dual wavelength laser passing in the same channel.Experiments were carried out under the conditions of different concentration fume and dust.It was found that attenuation coefficient linearly changed with air vapor density,the attenuation coefficient changed smaller with longer wavelength,and that it tend to the same when fume density reached to some extent.On the basis of measurement data,transmittance changed with dust concentration exponentially,which coincided with Beer-Lambert law.Experimental test data results accorded with atmospheric scattering theory.The results have reference value to study about atmospheric influence on light.
In order to study effect of atmospheric channel on the beam quality under special circumstances,an indoor experiment system was built to simulate the situation dual wavelength laser passing in the same channel.Experiments were carried out under the conditions of different concentration fume and dust.It was found that attenuation coefficient linearly changed with air vapor density,the attenuation coefficient changed smaller with longer wavelength,and that it tend to the same when fume density reached to some extent.On the basis of measurement data,transmittance changed with dust concentration exponentially,which coincided with Beer-Lambert law.Experimental test data results accorded with atmospheric scattering theory.The results have reference value to study about atmospheric influence on light.
2010, 34(4): 482-485.
doi: 10.3969/j.issn.1001-3806.2010.04.014
Abstract:
In order to investigate the effect of laser shot peening upon the growth of fatigue cracks,definite element analysis softwares,i.e.,finite element analysis code ABAQUS and MSC.Fatigue were used to simulate the distribution of compressive residual stress,the fatigue life,rate of crack growth and the size of final crack with different laser peening times from one to three on compact tension (CT) specimens of 6061-T6 aluminum alloy.Based on theoretical analysis,the forecasting model of fatigue life for laser shot peening (LSP) process was established.The residual stress field induced by LSP was analyzed with ABAQUS code firstly,and then the stress field model was imported into MSC.Fatigue code for the crack growth analysis.It showed that LSP could effectively inhibit the crack growth,decrease the rate of crack growth as well as the size of final crack,and then the fatigue life was extended.The increase of peening times could increase the effect of LSP to some extent.However,the effect gradually became weak.The results afford a foundation for theoretical analysis and experiments about the effect of laser shot peening upon the growth of fatigue cracks.
In order to investigate the effect of laser shot peening upon the growth of fatigue cracks,definite element analysis softwares,i.e.,finite element analysis code ABAQUS and MSC.Fatigue were used to simulate the distribution of compressive residual stress,the fatigue life,rate of crack growth and the size of final crack with different laser peening times from one to three on compact tension (CT) specimens of 6061-T6 aluminum alloy.Based on theoretical analysis,the forecasting model of fatigue life for laser shot peening (LSP) process was established.The residual stress field induced by LSP was analyzed with ABAQUS code firstly,and then the stress field model was imported into MSC.Fatigue code for the crack growth analysis.It showed that LSP could effectively inhibit the crack growth,decrease the rate of crack growth as well as the size of final crack,and then the fatigue life was extended.The increase of peening times could increase the effect of LSP to some extent.However,the effect gradually became weak.The results afford a foundation for theoretical analysis and experiments about the effect of laser shot peening upon the growth of fatigue cracks.
2010, 34(4): 486-488,492.
doi: 10.3969/j.issn.1001-3806.2010.04.015
Abstract:
In order to obtain the filtering characteristics of photonic crystals with symmetrical structure and asymmetrical structure,the influence of refractive index ratio for both the structures was analyzed based on the transfer matrix method.The results indicate that the photonic crystals with symmetrical structure have narrow-band filtering characteristics at selected incident angles.However,it is not suitable for weak signal detection.Their transmission bandwidth is narrower when the outer layer of multi-layer coating films is at high refractive index.The photonic crystals with asymmetrical structure have band-stop filtering characteristics and the characteristics maintain the same for any sequence of high or low refractive index.The theoretical analysis and simulation results provide the theory for developing narrow-band and band-stop filters.
In order to obtain the filtering characteristics of photonic crystals with symmetrical structure and asymmetrical structure,the influence of refractive index ratio for both the structures was analyzed based on the transfer matrix method.The results indicate that the photonic crystals with symmetrical structure have narrow-band filtering characteristics at selected incident angles.However,it is not suitable for weak signal detection.Their transmission bandwidth is narrower when the outer layer of multi-layer coating films is at high refractive index.The photonic crystals with asymmetrical structure have band-stop filtering characteristics and the characteristics maintain the same for any sequence of high or low refractive index.The theoretical analysis and simulation results provide the theory for developing narrow-band and band-stop filters.
2010, 34(4): 489-492.
doi: 10.3969/j.issn.1001-3806.2010.04.016
Abstract:
Taking into account the linear loss and biphotonic absorption effect of silicon-on-insulator (SOI) waveguide simultaneously,condition and gain spectra of modulation instability (MI) induced by combined effects of self-phase modulation and waveguide dispersions were investigated.Formulation for calculating the gain of MI was deduced theoretically,and expressions of peak gain,peak gain frequency and bandwidth of modulation instability were obtained as well.Impacts of various parameters on gain spectra of MI were analyzed theoretically and simulated in detail.Both theoretical analysis and simulation show that strong MI takes place even in the existence of low light power.The peak gain of MI is 2 to 3 orders of magnitude larger than that achieved in optical fibers with the same light power.Both peak gain frequency and bandwidth of gain spectra of MI are decreased exponentially with linear loss of waveguide,and peak gain is decreased exponentially with bi-photonic absorption of waveguide as well.The work provides an important reference for experimentally investigating modulation instability and supercontinuum generation in silicon waveguide.
Taking into account the linear loss and biphotonic absorption effect of silicon-on-insulator (SOI) waveguide simultaneously,condition and gain spectra of modulation instability (MI) induced by combined effects of self-phase modulation and waveguide dispersions were investigated.Formulation for calculating the gain of MI was deduced theoretically,and expressions of peak gain,peak gain frequency and bandwidth of modulation instability were obtained as well.Impacts of various parameters on gain spectra of MI were analyzed theoretically and simulated in detail.Both theoretical analysis and simulation show that strong MI takes place even in the existence of low light power.The peak gain of MI is 2 to 3 orders of magnitude larger than that achieved in optical fibers with the same light power.Both peak gain frequency and bandwidth of gain spectra of MI are decreased exponentially with linear loss of waveguide,and peak gain is decreased exponentially with bi-photonic absorption of waveguide as well.The work provides an important reference for experimentally investigating modulation instability and supercontinuum generation in silicon waveguide.
2010, 34(4): 493-496,501.
doi: 10.3969/j.issn.1001-3806.2010.04.017
Abstract:
In order to increase measurement precision and overcome discontinuous phase unwrapping in the 3-D shape measurement of discontinuous objects,an improved Fourier transform profilometry(FTP) was presented with a grid fringe pattern as spatial carrier-fringes.Two 1-D deformed grating patterns were extracted from the deformed grid fringe pattern using 2-D Fourier transform and fixed bandwidth filters.Two wrapped phases were obtained from these both one-dimension deformed patterns,respectively,and the corresponding unwrapped phases were achieved by means of a lookup table method.The experimental results show that the technique can overcome the low measurement precision using 1-D single frequency fringe pattern,the possible frequency overlaps using 1-D dual-frequency fringe pattern and tolerate the height discontinuity of the 3-D shape measurement; the above method is available.
In order to increase measurement precision and overcome discontinuous phase unwrapping in the 3-D shape measurement of discontinuous objects,an improved Fourier transform profilometry(FTP) was presented with a grid fringe pattern as spatial carrier-fringes.Two 1-D deformed grating patterns were extracted from the deformed grid fringe pattern using 2-D Fourier transform and fixed bandwidth filters.Two wrapped phases were obtained from these both one-dimension deformed patterns,respectively,and the corresponding unwrapped phases were achieved by means of a lookup table method.The experimental results show that the technique can overcome the low measurement precision using 1-D single frequency fringe pattern,the possible frequency overlaps using 1-D dual-frequency fringe pattern and tolerate the height discontinuity of the 3-D shape measurement; the above method is available.
2010, 34(4): 497-501.
doi: 10.3969/j.issn.1001-3806.2010.04.018
Abstract:
In order to obtain accurate information of ship wake and the detection range auto-adaptively,based on the characteristics of the backscattering optical wake signal,the minimum screening method was used to process the baekscattering signal.After anti-ground noise,based on the criterion of least mean-squared error,with the wake flow backseattering optical signal subtracting the water baekscattering optical signal,the pure wake signal was obtained.A simple model of the pure wake signal was built,based on which the relevant information of the wake thickness was obtained.The results are helpful to judge and identify the wake character information.
In order to obtain accurate information of ship wake and the detection range auto-adaptively,based on the characteristics of the backscattering optical wake signal,the minimum screening method was used to process the baekscattering signal.After anti-ground noise,based on the criterion of least mean-squared error,with the wake flow backseattering optical signal subtracting the water baekscattering optical signal,the pure wake signal was obtained.A simple model of the pure wake signal was built,based on which the relevant information of the wake thickness was obtained.The results are helpful to judge and identify the wake character information.
2010, 34(4): 502-505.
doi: 10.3969/j.issn.1001-3806.2010.04.019
Abstract:
In order to study the strain of rock under pressure in real time and conveniently,real-time digital holographic method was adopted.With a 15cm × 15cm×1.5cm rock loaded in a 3-D afterburner shelf,the rock stress field distribution and evolution of the interference fringes under different conditions in the process of compression strain were collected and recorded with a CMOS in real-time digital holographic optical path.Then,this video file was restored with MATLAB and the rock at ambient temperature conditions,the pre-drilling strain under the conditions of pressure changes in real time were obtained.The results show that real-time digital holographic method is a high-precision,non-destructive detection method.Real-time digital holographic method can detect the real time tress conveniently and fast not only on the rock but also on other similar materials.
In order to study the strain of rock under pressure in real time and conveniently,real-time digital holographic method was adopted.With a 15cm × 15cm×1.5cm rock loaded in a 3-D afterburner shelf,the rock stress field distribution and evolution of the interference fringes under different conditions in the process of compression strain were collected and recorded with a CMOS in real-time digital holographic optical path.Then,this video file was restored with MATLAB and the rock at ambient temperature conditions,the pre-drilling strain under the conditions of pressure changes in real time were obtained.The results show that real-time digital holographic method is a high-precision,non-destructive detection method.Real-time digital holographic method can detect the real time tress conveniently and fast not only on the rock but also on other similar materials.
2010, 34(4): 506-509.
doi: 10.3969/j.issn.1001-3806.2010.04.020
Abstract:
In order to weld ultra-thin T2 copper with high reflectivity by means of Nd:YAG laser at 1.064μm,based on orthogonal test method,effects of pulse peak current,its duration and frequency on maximum shear stress were studied under the conditions of nitrogen protection,+2mm defocusing amount and 1.5mm/s welding speed.The relationships between maximum shear stress and pulse peak current,its duration and frequency were obtained in the experiments; the welding surface and its microstructure were observed.The results show that the ultra-thin copper with high reflectivity can be well spot-welded by means of Nd:YAG laser at 1.064μm,based on design of processing parameters such as the laser pulse shape.
In order to weld ultra-thin T2 copper with high reflectivity by means of Nd:YAG laser at 1.064μm,based on orthogonal test method,effects of pulse peak current,its duration and frequency on maximum shear stress were studied under the conditions of nitrogen protection,+2mm defocusing amount and 1.5mm/s welding speed.The relationships between maximum shear stress and pulse peak current,its duration and frequency were obtained in the experiments; the welding surface and its microstructure were observed.The results show that the ultra-thin copper with high reflectivity can be well spot-welded by means of Nd:YAG laser at 1.064μm,based on design of processing parameters such as the laser pulse shape.
2010, 34(4): 510-513.
doi: 10.3969/j.issn.1001-3806.2010.04.021
Abstract:
In order to study the effects on visible CCD array irradiated by XeF(C-A) laser and YAG frequency-doubled laser,the experimental platform for pulse laser radiating CCD and CCD synchronous image-acquiring system were set up.Based on the experimental platform and the acquiring system,the radiating effect experiments on CCD by the both lasers were carried out,laser energy thresholds and CCD images under soft damage (including local saturation,full saturation,saturation crosstalk,full-screen saturation) were acquired.The data and CCD images were processed and analyzed by means of laser energy density threshold method and saturated area method respectively.The results show that XeF(C-A) blue-green laser and YAG frequencydoubled laser have the same radiating effects on SONY SUPER HAD visible CCD array.
In order to study the effects on visible CCD array irradiated by XeF(C-A) laser and YAG frequency-doubled laser,the experimental platform for pulse laser radiating CCD and CCD synchronous image-acquiring system were set up.Based on the experimental platform and the acquiring system,the radiating effect experiments on CCD by the both lasers were carried out,laser energy thresholds and CCD images under soft damage (including local saturation,full saturation,saturation crosstalk,full-screen saturation) were acquired.The data and CCD images were processed and analyzed by means of laser energy density threshold method and saturated area method respectively.The results show that XeF(C-A) blue-green laser and YAG frequencydoubled laser have the same radiating effects on SONY SUPER HAD visible CCD array.
2010, 34(4): 514-516.
doi: 10.3969/j.issn.1001-3806.2010.04.022
Abstract:
In order to study the surface microstructure and property variation of ultrahigh carbon steel after laser treating,ultrahigh carbon steel(mass fraction of C is 0.016) was treated with 2kW continuous wave CO2 laser.Then its microstructure was observed with a scanning electron microscope and its hardness was measured with a microhardness tester.Through theoretical analysis and experiments verification,the microstructure and microhardness curve along the depth direction were obtained.The results show that the laser treated layer includes surface melted layer,overheating layer and transformation hardening layer.The melted layer is composed of cystiform-dendritic and divorced eutectic.The grain size in transformation hardening layer is finer than that in other layers,its microhardness is higher and its hardness can reach 750HV～905HV,which indicates a typical laser quenching microstructure.With the increase of laser power (1000W～1200W),the volume fraction of cystiform-dendritic and divorced eutectic in melted layer increased,however the quantities of martensite decreased,each layer's width and depth were reduced,and microhardness decreased.It is helpful to refine microstructure of ultrahigh carbon steel and improve its property.
In order to study the surface microstructure and property variation of ultrahigh carbon steel after laser treating,ultrahigh carbon steel(mass fraction of C is 0.016) was treated with 2kW continuous wave CO2 laser.Then its microstructure was observed with a scanning electron microscope and its hardness was measured with a microhardness tester.Through theoretical analysis and experiments verification,the microstructure and microhardness curve along the depth direction were obtained.The results show that the laser treated layer includes surface melted layer,overheating layer and transformation hardening layer.The melted layer is composed of cystiform-dendritic and divorced eutectic.The grain size in transformation hardening layer is finer than that in other layers,its microhardness is higher and its hardness can reach 750HV～905HV,which indicates a typical laser quenching microstructure.With the increase of laser power (1000W～1200W),the volume fraction of cystiform-dendritic and divorced eutectic in melted layer increased,however the quantities of martensite decreased,each layer's width and depth were reduced,and microhardness decreased.It is helpful to refine microstructure of ultrahigh carbon steel and improve its property.
2010, 34(4): 517-519.
doi: 10.3969/j.issn.1001-3806.2010.04.023
Abstract:
Based on integrating sphere absolute method,temperature-dependent absorptivity of 30CrMnSiA carbon steel was measured with heating laser beam(λ=1064nm) and probing laser beam (λ=1319nm) irradiating on material surface in atmosphere environment at the same time.With the probing laser incident at zero and thirty degrees,the absorptivity of the steel was measured at the temperature range from the room temperature to melting point.It was 0.4 at room temperature and 0.9 at melting point.The results show that temperature has important effect on the absorptivity of 30CrMnSiA carbon steel in atmosphere environment,however the incidence angle hasn't any effect on absorptivity.
Based on integrating sphere absolute method,temperature-dependent absorptivity of 30CrMnSiA carbon steel was measured with heating laser beam(λ=1064nm) and probing laser beam (λ=1319nm) irradiating on material surface in atmosphere environment at the same time.With the probing laser incident at zero and thirty degrees,the absorptivity of the steel was measured at the temperature range from the room temperature to melting point.It was 0.4 at room temperature and 0.9 at melting point.The results show that temperature has important effect on the absorptivity of 30CrMnSiA carbon steel in atmosphere environment,however the incidence angle hasn't any effect on absorptivity.
2010, 34(4): 520-524.
doi: 10.3969/j.issn.1001-3806.2010.04.024
Abstract:
In order to study the focusing properties of Gaussian beams passing through a compound optical system consisting of two thin piano-convex lens,the formulae of the waist radius and imaging distance of focused Gaussian beams were deduced based on the matrix optical method.Then effect of various parameters in the optical system on its stability property and the waist radius was simulated by means of numerical calculation.Finally,the focusing properties of Gaussian beams passing through the compound optical system was discussed.The results showed that the system was capable of achieving both stability and smaller focused waist radius.The focus radius of about 2μm was achieved in the experiments,which proved the correctness of the theoretical analysis.The study built a foundation for the design of a solid state laser.
In order to study the focusing properties of Gaussian beams passing through a compound optical system consisting of two thin piano-convex lens,the formulae of the waist radius and imaging distance of focused Gaussian beams were deduced based on the matrix optical method.Then effect of various parameters in the optical system on its stability property and the waist radius was simulated by means of numerical calculation.Finally,the focusing properties of Gaussian beams passing through the compound optical system was discussed.The results showed that the system was capable of achieving both stability and smaller focused waist radius.The focus radius of about 2μm was achieved in the experiments,which proved the correctness of the theoretical analysis.The study built a foundation for the design of a solid state laser.
2010, 34(4): 525-528.
doi: 10.3969/j.issn.1001-3806.2010.04.025
Abstract:
In order to grasp the influence of the discharge tube structure on the flow field and working performance of a high power CO2 laser and get a more uniform and stable glow discharge,numerical simulation of the flowing status in discharge tube was done and the computational results matched the experiments results well.The flow fields of different tubes were compared.A new discharge tube structure was designed.The results showed that the flowing field characteristics influenced the uniformity and stability of the glow discharge in tubes.A more uniform flow field and discharge could be got in the new tube needing more optimization.
In order to grasp the influence of the discharge tube structure on the flow field and working performance of a high power CO2 laser and get a more uniform and stable glow discharge,numerical simulation of the flowing status in discharge tube was done and the computational results matched the experiments results well.The flow fields of different tubes were compared.A new discharge tube structure was designed.The results showed that the flowing field characteristics influenced the uniformity and stability of the glow discharge in tubes.A more uniform flow field and discharge could be got in the new tube needing more optimization.
2010, 34(4): 529-531,551.
doi: 10.3969/j.issn.1001-3806.2010.04.026
Abstract:
For a new developed excimer laser system,the performance of laser gas is very important for the scale of the hybrid gas is closely relative to single pulse energy,stability of discharge,laser lifetime and so on.In order to obtain the optimum premix gas component,the corresponding experiments were accomplished in the own developed compact XeCl excimer laser system.The influence of Xe,HCl gas on the performance was analyzed.For both Ne and He buffer gas,the difference of the excimer laser performance was obtained by the theoretical analysis and experimental result.The optimum gas composition as well as the method to enhance laser efficiency was achieved by the relevant experiments results.The results provide the support and the warrant for developing commercial compact excimer laser.
For a new developed excimer laser system,the performance of laser gas is very important for the scale of the hybrid gas is closely relative to single pulse energy,stability of discharge,laser lifetime and so on.In order to obtain the optimum premix gas component,the corresponding experiments were accomplished in the own developed compact XeCl excimer laser system.The influence of Xe,HCl gas on the performance was analyzed.For both Ne and He buffer gas,the difference of the excimer laser performance was obtained by the theoretical analysis and experimental result.The optimum gas composition as well as the method to enhance laser efficiency was achieved by the relevant experiments results.The results provide the support and the warrant for developing commercial compact excimer laser.
2010, 34(4): 532-534.
doi: 10.3969/j.issn.1001-3806.2010.04.027
Abstract:
For studying the wander of laser beam through atmosphere,the propagation of a laser beam through atmosphere was studied experimentally.The wander of light spots was measured by means of CCD imaging technique.The spot wander in horizontal and vertical direction was studied and the influence of crosswind on the spot wander was analyzed.The spot wander was obtained at different time and distance.The experimental result shows that the spot wander in both the directions can reach unanimity gradually with the increasing distances.
For studying the wander of laser beam through atmosphere,the propagation of a laser beam through atmosphere was studied experimentally.The wander of light spots was measured by means of CCD imaging technique.The spot wander in horizontal and vertical direction was studied and the influence of crosswind on the spot wander was analyzed.The spot wander was obtained at different time and distance.The experimental result shows that the spot wander in both the directions can reach unanimity gradually with the increasing distances.
2010, 34(4): 535-537,541.
doi: 10.3969/j.issn.1001-3806.2010.04.028
Abstract:
In order for the laser angle deception jamming equipment on a warship platform to interfere with guided weapons taking the offing as a false target reflector,a number of factors affecting the offshore laser reflectivity were analyzed.Then the onthe -spot measurement method,data processing method and requirements of measuring equipment were put forward.In practice,this method is the most direct and effective technical means for understanding and grasping the reflection of offshore laser under different sea state conditions.The study results can provide the basic data for research,development and application of the shipborne laser equipment.
In order for the laser angle deception jamming equipment on a warship platform to interfere with guided weapons taking the offing as a false target reflector,a number of factors affecting the offshore laser reflectivity were analyzed.Then the onthe -spot measurement method,data processing method and requirements of measuring equipment were put forward.In practice,this method is the most direct and effective technical means for understanding and grasping the reflection of offshore laser under different sea state conditions.The study results can provide the basic data for research,development and application of the shipborne laser equipment.
2010, 34(4): 538-541.
doi: 10.3969/j.issn.1001-3806.2010.04.029
Abstract:
To order to achieve the application of synthetic aperture ladar (SAL) in target detection,the characteristics and strong points of SAL in returning wave signal-to-noise ratio(SNR),detecting range,synthetic aperture time and linear frequency modulation orad demodulation were theoretically analyzed based on the signal transmission model and returning wave model.The performances were compared with traditional heterodyne ladar and synthetic aperture radar(SAR).The results show that SAL has higher returning wave SNR and farther detecting range than traditional heterodyne ladar,and the imaging speed is faster than SAR,which benefit the application of SAL on long range target detecting,tracking and fast early warning.
To order to achieve the application of synthetic aperture ladar (SAL) in target detection,the characteristics and strong points of SAL in returning wave signal-to-noise ratio(SNR),detecting range,synthetic aperture time and linear frequency modulation orad demodulation were theoretically analyzed based on the signal transmission model and returning wave model.The performances were compared with traditional heterodyne ladar and synthetic aperture radar(SAR).The results show that SAL has higher returning wave SNR and farther detecting range than traditional heterodyne ladar,and the imaging speed is faster than SAR,which benefit the application of SAL on long range target detecting,tracking and fast early warning.
2010, 34(4): 542-547.
doi: 10.3969/j.issn.1001-3806.2010.04.030
Abstract:
In order to study propagation properties of partially coherent flat-topped (PCFT) beam array in a turbulent atmosphere,corresponding analytical formulate were derived based on the extend Huygens-Fresnel integral and numerical simulation was carried out with MATHEMATICA.The results indicate that for certain turbulence,the smaller coherence length,the faster it becomes Gaussian beam.The influence of atmospheric turbulence on the relative beam width spreading is larger for PCFT beam array with larger beam order and smaller coherence length.The strehl ratio of PCFT beam array with smaller coherence length and bigger beam order are less affected by turbulence.In the far field,for different beam order,if the bucket radius is four times smaller than the waist width of beams,the power in the bucket(PIB) is larger for PCFT beam array with the higher beam order.However,if the bucket radius is four times larger than the waist width of beams,its PIB is smaller.For different coherence length,when the bucket radius is four times smaller than the waist width of beams,the PIB is larger for PCFT beam array with the smaller coherence length,but its PIB is smaller when the bucket radius is four times larger than the waist width of beams.These results are useful for laser communication application.
In order to study propagation properties of partially coherent flat-topped (PCFT) beam array in a turbulent atmosphere,corresponding analytical formulate were derived based on the extend Huygens-Fresnel integral and numerical simulation was carried out with MATHEMATICA.The results indicate that for certain turbulence,the smaller coherence length,the faster it becomes Gaussian beam.The influence of atmospheric turbulence on the relative beam width spreading is larger for PCFT beam array with larger beam order and smaller coherence length.The strehl ratio of PCFT beam array with smaller coherence length and bigger beam order are less affected by turbulence.In the far field,for different beam order,if the bucket radius is four times smaller than the waist width of beams,the power in the bucket(PIB) is larger for PCFT beam array with the higher beam order.However,if the bucket radius is four times larger than the waist width of beams,its PIB is smaller.For different coherence length,when the bucket radius is four times smaller than the waist width of beams,the PIB is larger for PCFT beam array with the smaller coherence length,but its PIB is smaller when the bucket radius is four times larger than the waist width of beams.These results are useful for laser communication application.
2010, 34(4): 548-551.
doi: 10.3969/j.issn.1001-3806.2010.04.031
Abstract:
Effect of temperature on the dynamical evolution and self-deflection characteristics of bright screening photovoltaic spatial solitons in two-photon photovoltaic photorefractive media was investigated.Taking the bright solitons as the input solitary beam,numerically solving the beam propagation equation,it was found that the intensity profile and the full-width at half maximum of bright screening photovoltaic spatial solitons decreased with the raising of the temperature in a certain range of temperature.When the temperature of crystals changed in a small range,the stability of solitons could be persisted by overcoming the small perturbation.Solitons would become unstable or collapse when the crystal changed in a large range.The results show that the bending distance of the bright solitary beam centre increases with temperature rise,then reaches its maximum value at a specific temperature,and after that,decreases as temperature continuously rises.All of these results are benefit for the development of theory of two-photon spatial solitons.
Effect of temperature on the dynamical evolution and self-deflection characteristics of bright screening photovoltaic spatial solitons in two-photon photovoltaic photorefractive media was investigated.Taking the bright solitons as the input solitary beam,numerically solving the beam propagation equation,it was found that the intensity profile and the full-width at half maximum of bright screening photovoltaic spatial solitons decreased with the raising of the temperature in a certain range of temperature.When the temperature of crystals changed in a small range,the stability of solitons could be persisted by overcoming the small perturbation.Solitons would become unstable or collapse when the crystal changed in a large range.The results show that the bending distance of the bright solitary beam centre increases with temperature rise,then reaches its maximum value at a specific temperature,and after that,decreases as temperature continuously rises.All of these results are benefit for the development of theory of two-photon spatial solitons.
2010, 34(4): 552-556.
doi: 10.3969/j.issn.1001-3806.2010.04.032
Abstract:
In order to study the influence of laser shock processing(LSP) and different laser shock model on the mechanical properties of magnesium alloy,an AZ91 magnesium alloy specimen was processed with two beams of nonsuperimposed Nd:glass laser pulses.The surface morphology,with an oval spot distribution,was observed and analyzed after shock,and then the model was compared with the traditional model of single-point-superposition.The nano-hardness of the shocked and non-shocked region was measured with a triboindenter nano-indentation instrument,and the measured value was 1.59GPa and 1.47GPa respectively.The residual stress in the shocked region was measured with a X2350A X-ray strain instrument,and the stress was simulated by means of the finite element software ABAQUS.Both experimental and simulation results were in good agreement,and showed that there was high residual stress distribution,about-120MPa in the shocked region.The results show that the non-superposition of dual-beam mode can improve the shock efficiency.The LSP can improve the nano-hardness and mechanical properties of magnesium alloy and enhance its resistance to foreign objects damages and antifatigue properties.
In order to study the influence of laser shock processing(LSP) and different laser shock model on the mechanical properties of magnesium alloy,an AZ91 magnesium alloy specimen was processed with two beams of nonsuperimposed Nd:glass laser pulses.The surface morphology,with an oval spot distribution,was observed and analyzed after shock,and then the model was compared with the traditional model of single-point-superposition.The nano-hardness of the shocked and non-shocked region was measured with a triboindenter nano-indentation instrument,and the measured value was 1.59GPa and 1.47GPa respectively.The residual stress in the shocked region was measured with a X2350A X-ray strain instrument,and the stress was simulated by means of the finite element software ABAQUS.Both experimental and simulation results were in good agreement,and showed that there was high residual stress distribution,about-120MPa in the shocked region.The results show that the non-superposition of dual-beam mode can improve the shock efficiency.The LSP can improve the nano-hardness and mechanical properties of magnesium alloy and enhance its resistance to foreign objects damages and antifatigue properties.
2010, 34(4): 557-560,576.
doi: 10.3969/j.issn.1001-3806.2010.04.033
Abstract:
In order to optimize an omni-direction laser warning system based on diffusive reflection detection,using the method of theoretical derivation and experiment analyzing,the imaging rule of a fish-eye lens was deduced and discussed by means of theoretical derivation and experiment.The power function of the receiving signal was deduced.The illumination uniformity of the image-plane and imaging characteristics of CCD were discussed.The formula of the number of imaging elements was deduced.For different imaging elements,the power formula of one imaging element was put forward.The graphs of relation between the number of imaging elements and the distance d between the detector and the facula was provided.At different visible range,the graphs of power of one imaging element related with the transmission distance R and with distance d were shown.The obtained results offer performance guidance for design,development and optimization of an omni-direction laser warning system based on diffusive reflection detection.
In order to optimize an omni-direction laser warning system based on diffusive reflection detection,using the method of theoretical derivation and experiment analyzing,the imaging rule of a fish-eye lens was deduced and discussed by means of theoretical derivation and experiment.The power function of the receiving signal was deduced.The illumination uniformity of the image-plane and imaging characteristics of CCD were discussed.The formula of the number of imaging elements was deduced.For different imaging elements,the power formula of one imaging element was put forward.The graphs of relation between the number of imaging elements and the distance d between the detector and the facula was provided.At different visible range,the graphs of power of one imaging element related with the transmission distance R and with distance d were shown.The obtained results offer performance guidance for design,development and optimization of an omni-direction laser warning system based on diffusive reflection detection.
2010, 34(4): 561-564.
doi: 10.3969/j.issn.1001-3806.2010.04.034
Abstract:
In order to discuss the effect of laser energy density on the dimension of nylon12/HDPE (high density polyethylene) product,experiments of sintering nylon12/HDPE were carried out with CO2 laser based on the selective laser sintering technology.The microstructure of laser-sintering nylon12/HDPE was examined by means of scanning electron microscopy.It is concluded that warping will increase with the ratio of power/velocity (P/v) increasing.Optimum laser energy densitv P/v=0.8% while warping is about 0.4mm.This study is helpful to sinter the composite of nylon powder.
In order to discuss the effect of laser energy density on the dimension of nylon12/HDPE (high density polyethylene) product,experiments of sintering nylon12/HDPE were carried out with CO2 laser based on the selective laser sintering technology.The microstructure of laser-sintering nylon12/HDPE was examined by means of scanning electron microscopy.It is concluded that warping will increase with the ratio of power/velocity (P/v) increasing.Optimum laser energy densitv P/v=0.8% while warping is about 0.4mm.This study is helpful to sinter the composite of nylon powder.
2010, 34(4): 565-568.
doi: 10.3969/j.issn.1001-3806.2010.04.035
Abstract:
In order to study propagation properties of J0-correlated partially coherent flat-topped beams in atmospheric turbulence,the average intensity distribution were derived based on extended Huygens-Fresnel principle,and the analytical expression of beams waist width was obtained with the second-order moment method.Then,the effects of propagation distance,correlation lengths of source,structure constant and orders of flat-topped beams on average intensity distribution and beam width were analyzed.It was show that higher order flat-topped beam was less affected by atmospheric turbulence and it was less broadened.Results also show that maximum central intensity value can be obtained by adjusting the correlation lengths of source.
In order to study propagation properties of J0-correlated partially coherent flat-topped beams in atmospheric turbulence,the average intensity distribution were derived based on extended Huygens-Fresnel principle,and the analytical expression of beams waist width was obtained with the second-order moment method.Then,the effects of propagation distance,correlation lengths of source,structure constant and orders of flat-topped beams on average intensity distribution and beam width were analyzed.It was show that higher order flat-topped beam was less affected by atmospheric turbulence and it was less broadened.Results also show that maximum central intensity value can be obtained by adjusting the correlation lengths of source.
2010, 34(4): 569-572.
doi: 10.3969/j.issn.1001-3806.2010.04.036
Abstract:
In order to study the effect of the parameters of double beams combination system on far field combined beams,it was simulated with ZEMAX software and its theoretical result was put forward.After comparison,it was found that the simulated results were similar to the theoretical ones.The calculation theory is suitable for far field beam combination,which affords important references for parameters setting in a double-beam combination system.
In order to study the effect of the parameters of double beams combination system on far field combined beams,it was simulated with ZEMAX software and its theoretical result was put forward.After comparison,it was found that the simulated results were similar to the theoretical ones.The calculation theory is suitable for far field beam combination,which affords important references for parameters setting in a double-beam combination system.
2010, 34(4): 573-576.
doi: 10.3969/j.issn.1001-3806.2010.04.037
Abstract:
Taking example for sine wave and triangle wave,this paper analyzes analog optical signal's cross phase modulation characteristics in semiconductor optical amplifier,including gain,nonlinear phase difference and chirp.Analysis shows that when using the frame synchronization between signal light and optical control pulse,the gain and gain difference at each point of signal pulse will fluctuate,the nonlinear phase difference also will deviate from the ideal value of π.In order to obtain the same nonlinear phase difference at different point of signal pulse,bit synchronization mode should be used,and the needed optical control pulse has the similar waveform to optical signal pulse.
Taking example for sine wave and triangle wave,this paper analyzes analog optical signal's cross phase modulation characteristics in semiconductor optical amplifier,including gain,nonlinear phase difference and chirp.Analysis shows that when using the frame synchronization between signal light and optical control pulse,the gain and gain difference at each point of signal pulse will fluctuate,the nonlinear phase difference also will deviate from the ideal value of π.In order to obtain the same nonlinear phase difference at different point of signal pulse,bit synchronization mode should be used,and the needed optical control pulse has the similar waveform to optical signal pulse.
