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RSS2010 Vol. 34, No. 3
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2010, 34(3): 289-293.
doi: 10.3969/j.issn.1001-3806.2010.03.001
[Abstract]
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Abstract:
In order to rapidly manufacture jaw models and transfer tray used in orthodontic field,computer tomography scanning data,three-dimension reverse engineering and rapid prototyping technology were combined.Jaw models were manufactured by means of selective laser sintering and stereo lithography apparatus respectively.The way fabricating jaw and brackets combination by selective laser melting,then suction plastic to acquire transfer tray was emphasized.Results indicate that jaw models have fine dimensional accuracy and transfer tray match well with brackets.This method provides a new idea for orthodontic doctors to diagnose and treat the sick,and a new strategy to mount and fix brackets.
In order to rapidly manufacture jaw models and transfer tray used in orthodontic field,computer tomography scanning data,three-dimension reverse engineering and rapid prototyping technology were combined.Jaw models were manufactured by means of selective laser sintering and stereo lithography apparatus respectively.The way fabricating jaw and brackets combination by selective laser melting,then suction plastic to acquire transfer tray was emphasized.Results indicate that jaw models have fine dimensional accuracy and transfer tray match well with brackets.This method provides a new idea for orthodontic doctors to diagnose and treat the sick,and a new strategy to mount and fix brackets.
2010, 34(3): 294-296,315.
doi: 10.3969/j.issn.1001-3806.2010.03.002
Abstract:
In order to study the effect of the structure of photonic crystal on electromagnetic wave transmission characteristics,a new 2-D hybrid photonic crystal structure was proposed.By means of finite difference time domain method,the optical transmission properties of 2-D hybrid photonic crystals were studied.Furthermore,it was also studied how the shape and structural parameters affect transmission properties of photonic crystal.The results show that the new structure not only maintain the primary band gap of the former structures but also produce a new band gap.Compared to the compound dielectric cylinder,the simple one has riot produced a new band gap.Both increasing the width of medium plate and the radius of embedded concentric circle arc in favor of the new band gap emerging.The theory basis of the design of photonic devices is provided.
In order to study the effect of the structure of photonic crystal on electromagnetic wave transmission characteristics,a new 2-D hybrid photonic crystal structure was proposed.By means of finite difference time domain method,the optical transmission properties of 2-D hybrid photonic crystals were studied.Furthermore,it was also studied how the shape and structural parameters affect transmission properties of photonic crystal.The results show that the new structure not only maintain the primary band gap of the former structures but also produce a new band gap.Compared to the compound dielectric cylinder,the simple one has riot produced a new band gap.Both increasing the width of medium plate and the radius of embedded concentric circle arc in favor of the new band gap emerging.The theory basis of the design of photonic devices is provided.
2010, 34(3): 297-299.
doi: 10.3969/j.issn.1001-3806.2010.03.003
Abstract:
In order to eliminate the influences resulting from environmental disturbances,a stabilized optical fiber interferometric measurement system configured with a fiber 3×3 coupler and fiber Bragg gratings(FBGs)was designed.By employing the FBGs as in-fiber reflective mirrors,both fiber Michelson interferometers in the system shared a commoninterferometric -optical path.One of the fiber interferometers was used to stabilize the system based on a first order electronic feedback loop for compensating for the environment jitter,while the other was used to perform the measurement task.The bandwidth of the feedback loop is 21Hz which endows the system stabilization for on-line precision measurement.
In order to eliminate the influences resulting from environmental disturbances,a stabilized optical fiber interferometric measurement system configured with a fiber 3×3 coupler and fiber Bragg gratings(FBGs)was designed.By employing the FBGs as in-fiber reflective mirrors,both fiber Michelson interferometers in the system shared a commoninterferometric -optical path.One of the fiber interferometers was used to stabilize the system based on a first order electronic feedback loop for compensating for the environment jitter,while the other was used to perform the measurement task.The bandwidth of the feedback loop is 21Hz which endows the system stabilization for on-line precision measurement.
2010, 34(3): 300-302,319.
doi: 10.3969/j.issn.1001-3806.2010.03.004
Abstract:
In order to study the effect of powder feed parameters on the motive behavior of coaxial carrier-gas powder in laser cladding process,a digital particle image velocimetry(DPIV)test device was constructed,a special image processing software was designed for this system.Lots of tests were performed on powder transport with carrying gas.The precision of velocity vector map of the powder particles in the coaxial was determined,and distribution of powder concentration at longitudinal axis from the nozzle exit was measured with the varied powder feed rate parameters by means of DPIV.Experiments show that the velocity metal-powder particle is linear with the powder mass flow rate.The powder concentration hardly changes with various gas fluxes and constant feeding powder amount.Outside the powder mass flow rate range(0.33g/s～0.83g/s),the effect is lessened obviously.Because of the nozzle configuration of powder feed unit,powder flow has phenomena of expansion,focus and reexpansion along the nozzle exit.The focus distance and powder stream radius at the focus point also increase and locus depth decreases with increasing the gas flux.
In order to study the effect of powder feed parameters on the motive behavior of coaxial carrier-gas powder in laser cladding process,a digital particle image velocimetry(DPIV)test device was constructed,a special image processing software was designed for this system.Lots of tests were performed on powder transport with carrying gas.The precision of velocity vector map of the powder particles in the coaxial was determined,and distribution of powder concentration at longitudinal axis from the nozzle exit was measured with the varied powder feed rate parameters by means of DPIV.Experiments show that the velocity metal-powder particle is linear with the powder mass flow rate.The powder concentration hardly changes with various gas fluxes and constant feeding powder amount.Outside the powder mass flow rate range(0.33g/s～0.83g/s),the effect is lessened obviously.Because of the nozzle configuration of powder feed unit,powder flow has phenomena of expansion,focus and reexpansion along the nozzle exit.The focus distance and powder stream radius at the focus point also increase and locus depth decreases with increasing the gas flux.
2010, 34(3): 303-305,346.
doi: 10.3969/j.issn.1001-3806.2010.03.005
Abstract:
In order to study the effect of residual stress on the laser shock forming metal sheet,a high power Nd:glass laser was used to form the metal-sheet and then the residual stress distribution on the surface of metal sheet was tested by means of Xray diffraction method.It was found that there was large residual compress stress on the concave surface of metal-sheet,but low residual tensile stress on the fringe of convex surface.The residual stress increased with the increase of laser energy.When the laser energy came to a certain value,the residual compress stress reached its maximization.On the shock surface,the residual compress stress of shock point was maximal,the other compress stress decreased in a nonlinear way along the shock point and ultimately to zero.For laser shocking different aperture of mold with a laser beam in 8mm diameter,30J energy,there was a threshold for the aperture of the mould.The residual stress increased with the increase of aperture when the aperture was smaller than the threshold.However,it decreased with the increase of aperture when the aperture was larger than the threshold.The threshold aperture was about 20mm.The results are very important for study of the distribution and control of residual compress stress,play an important theoretical and engineering role in studying the material fatigue,stress corrosion resistance and capability of the surface.
In order to study the effect of residual stress on the laser shock forming metal sheet,a high power Nd:glass laser was used to form the metal-sheet and then the residual stress distribution on the surface of metal sheet was tested by means of Xray diffraction method.It was found that there was large residual compress stress on the concave surface of metal-sheet,but low residual tensile stress on the fringe of convex surface.The residual stress increased with the increase of laser energy.When the laser energy came to a certain value,the residual compress stress reached its maximization.On the shock surface,the residual compress stress of shock point was maximal,the other compress stress decreased in a nonlinear way along the shock point and ultimately to zero.For laser shocking different aperture of mold with a laser beam in 8mm diameter,30J energy,there was a threshold for the aperture of the mould.The residual stress increased with the increase of aperture when the aperture was smaller than the threshold.However,it decreased with the increase of aperture when the aperture was larger than the threshold.The threshold aperture was about 20mm.The results are very important for study of the distribution and control of residual compress stress,play an important theoretical and engineering role in studying the material fatigue,stress corrosion resistance and capability of the surface.
2010, 34(3): 306-308,338.
doi: 10.3969/j.issn.1001-3806.2010.03.006
Abstract:
In order to prepare Ni-based amorphous alloy coating on the surface of 45# steel substrate by means of pre-laser cladding method,using the principle of the three clusters and the amorphous line of the law of composition rules,choosing Ni42Zr30Ta28 alloying powder which has a great glass-forming ability in conventional preparation methods of amorphous alloys,the microstructure,mechanical and corrosion performance of the laser cladding coating were analyzed and tested in experiments under the conditions of different laser power.The micro-hardness,wear resistance,salt spray data were obtained.The results showed that:the laser cladding Ni42Zr30Ta28 amorphous composite coating included amorphous and Ni3Zr,Ni5Ta,Ni7Zr2 phase crystallization.Compared with 45# steel,the mechanical and corrosion performance of the amorphous alloy coating were improved greatly.When the laser power was 3300W,the micro-hardness of coating surface reached up to 1496.4HKThe superficial rate of wear was 0.778g·mm-2The corrosion resistance of the coating was improved due to the existence of amorphous.When the laser power was 3000W,the increased unit area weight of the test specimen was 0.0026g·mm-2,and the salt endurance was best.The results provide the theoretical base for large area amorphous composit coating used in high energy lasers.
In order to prepare Ni-based amorphous alloy coating on the surface of 45# steel substrate by means of pre-laser cladding method,using the principle of the three clusters and the amorphous line of the law of composition rules,choosing Ni42Zr30Ta28 alloying powder which has a great glass-forming ability in conventional preparation methods of amorphous alloys,the microstructure,mechanical and corrosion performance of the laser cladding coating were analyzed and tested in experiments under the conditions of different laser power.The micro-hardness,wear resistance,salt spray data were obtained.The results showed that:the laser cladding Ni42Zr30Ta28 amorphous composite coating included amorphous and Ni3Zr,Ni5Ta,Ni7Zr2 phase crystallization.Compared with 45# steel,the mechanical and corrosion performance of the amorphous alloy coating were improved greatly.When the laser power was 3300W,the micro-hardness of coating surface reached up to 1496.4HKThe superficial rate of wear was 0.778g·mm-2The corrosion resistance of the coating was improved due to the existence of amorphous.When the laser power was 3000W,the increased unit area weight of the test specimen was 0.0026g·mm-2,and the salt endurance was best.The results provide the theoretical base for large area amorphous composit coating used in high energy lasers.
2010, 34(3): 309-312.
doi: 10.3969/j.issn.1001-3806.2010.03.007
Abstract:
In order to study the impact of geometry of the transceiver in the non-line-of-sight system working at the wavelength of 1.06μm,based on a single-scatter atmospheric propagation model,the impact of the field-of-view(FOV)of the transceiver,pitching angle and transmitting distance on the received signal power and path loss was studied by means of numerical calculation.It is shown that a larger FOV may significantly enhance the detected laser power,while the increase of transmitter beam divergence does not make any difference.It is also indicated that decreasing either the apex angle of the transmitter or receiver makes the detection of the weak scattering signal more difficult while other parameters remain the same.It is shown that decreasing the apex angle of the transmitter appropriately helps the signal detection for a certain scattering angle and transmitting distance.These results are valuable in system design.
In order to study the impact of geometry of the transceiver in the non-line-of-sight system working at the wavelength of 1.06μm,based on a single-scatter atmospheric propagation model,the impact of the field-of-view(FOV)of the transceiver,pitching angle and transmitting distance on the received signal power and path loss was studied by means of numerical calculation.It is shown that a larger FOV may significantly enhance the detected laser power,while the increase of transmitter beam divergence does not make any difference.It is also indicated that decreasing either the apex angle of the transmitter or receiver makes the detection of the weak scattering signal more difficult while other parameters remain the same.It is shown that decreasing the apex angle of the transmitter appropriately helps the signal detection for a certain scattering angle and transmitting distance.These results are valuable in system design.
2010, 34(3): 313-315.
doi: 10.3969/j.issn.1001-3806.2010.03.008
Abstract:
In order to measure the refractive index of the salt solution so that its salinity can be obtained,a measurement method with optical fiber based on the Fresnel principle was put forward.Its principle was introduced and the experimental results were obtained.The experiments indicated that the resolution was smaller than 0.4%.This method is simple,fast,sensitive and accurate.It can be applied in real-time monitoring of the seawater salinity.It also can be widely used in the field of industrial online concentration or refractive detection.
In order to measure the refractive index of the salt solution so that its salinity can be obtained,a measurement method with optical fiber based on the Fresnel principle was put forward.Its principle was introduced and the experimental results were obtained.The experiments indicated that the resolution was smaller than 0.4%.This method is simple,fast,sensitive and accurate.It can be applied in real-time monitoring of the seawater salinity.It also can be widely used in the field of industrial online concentration or refractive detection.
2010, 34(3): 316-319.
doi: 10.3969/j.issn.1001-3806.2010.03.009
Abstract:
In order to prove the feasibility of using fiber to transmit light and using self-focus lens to collect feedback light,the collection efficiency model of self-focus lens was built,and then much attention was put on how the collection efficiency of the self-focus lenschanges with radius and working distance.The feasibility of using fiber to transmit light and using self-focus lens to collect feedback light is theoretically proved.Finally,the experimental facility was established,the experiments were carried out.The experimental results show that this new instrument can acquire fine signal at long working distance with little disturbance induced by environment.
In order to prove the feasibility of using fiber to transmit light and using self-focus lens to collect feedback light,the collection efficiency model of self-focus lens was built,and then much attention was put on how the collection efficiency of the self-focus lenschanges with radius and working distance.The feasibility of using fiber to transmit light and using self-focus lens to collect feedback light is theoretically proved.Finally,the experimental facility was established,the experiments were carried out.The experimental results show that this new instrument can acquire fine signal at long working distance with little disturbance induced by environment.
2010, 34(3): 320-322.
doi: 10.3969/j.issn.1001-3806.2010.03.010
Abstract:
In order to satisfy the measurement requirement of ultraviolet pulses in a large laser system,with a single mode ultraviolet fiber propagating and sampling the signal,the characteristics of the ultraviolet pulse propagating in linear media were analyzed in theory,and the factors affecting the measurement of the pulse shape were reviewed systematically.The pulse profiles were measured after the ultraviolet pulse propagating a single-mode pure silica fiber.It is shown that single-mode ultraviolet fiber is a preferable medium for nanosecond pulse.An ultraviolet fiber is not suitable for long distance transmission considering the great loss and the limitation of the sensitivity of the detector.These results are significant for the design of pulse profile measuring system of high power laser facility.
In order to satisfy the measurement requirement of ultraviolet pulses in a large laser system,with a single mode ultraviolet fiber propagating and sampling the signal,the characteristics of the ultraviolet pulse propagating in linear media were analyzed in theory,and the factors affecting the measurement of the pulse shape were reviewed systematically.The pulse profiles were measured after the ultraviolet pulse propagating a single-mode pure silica fiber.It is shown that single-mode ultraviolet fiber is a preferable medium for nanosecond pulse.An ultraviolet fiber is not suitable for long distance transmission considering the great loss and the limitation of the sensitivity of the detector.These results are significant for the design of pulse profile measuring system of high power laser facility.
2010, 34(3): 323-325.
doi: 10.3969/j.issn.1001-3806.2010.03.011
Abstract:
To improve the thermal effect of laser crystal,the rectangle thermal conduct model of laser crystal was established.The temperature distribution and end-thermal deformation of rectangle Nd:YVO4N/Nd:GdVO4/Nd:GdYVO4 laser crystals were obtained after solving Possion equation,and the optical path difference(OPD)induced by end-thermal deformation and the total OPD were calculated.After comparison,it was shown that in the same eondation,the highest central temperatures of the pumped face of Nd:YVO4,Nd:GdYVO4 and Nd:GdVO4 crystals were 320℃,342℃ and 190℃,the biggest total OPD were 1.7μm,2.11μm and 1.3μm respectively.The results show that the central temperature rise and the total OPD of Nd:GdYVO4 crystal are the smallest and it is fitter for the pumped face of LD with high power.The study shows that the OPD induced by end-thermal deformation have a large influence on thermal focal length of laser crystals for solid-state lasers with high power.
To improve the thermal effect of laser crystal,the rectangle thermal conduct model of laser crystal was established.The temperature distribution and end-thermal deformation of rectangle Nd:YVO4N/Nd:GdVO4/Nd:GdYVO4 laser crystals were obtained after solving Possion equation,and the optical path difference(OPD)induced by end-thermal deformation and the total OPD were calculated.After comparison,it was shown that in the same eondation,the highest central temperatures of the pumped face of Nd:YVO4,Nd:GdYVO4 and Nd:GdVO4 crystals were 320℃,342℃ and 190℃,the biggest total OPD were 1.7μm,2.11μm and 1.3μm respectively.The results show that the central temperature rise and the total OPD of Nd:GdYVO4 crystal are the smallest and it is fitter for the pumped face of LD with high power.The study shows that the OPD induced by end-thermal deformation have a large influence on thermal focal length of laser crystals for solid-state lasers with high power.
2010, 34(3): 326-330,334.
doi: 10.3969/j.issn.1001-3806.2010.03.012
Abstract:
In order to solve the coating's general peeling and cracking problems caused by thermal stress at high temperature,H13-TiC gradient composite coatings were made by laser cladding on the surface of H13 hot-work die steel substrates.Using scanning electron microscope,X-ray diffraction and energy dispersive spectrometry,the microstrueture and morphology,distribution of constituents,hardness and thermal stability were checked.The results show that the coating mainly consists of Fe-Cr,TiC,TiO4 and Fe7C3.Polyhedron and dendritic TiC particles were dispersed in the coating.With the rising of TiC,TiC particles become larger,the hardness of the gradient coating is gradually improved,the dendritic structure in the bonding zone become smaller,and their distribution is in gradient.After heating at high temperature of 600℃ and cooling in the air,the decrease of the hardness is the largest in remehing region among the layers,while the substrate H13 steel is in the second place.On the whole,the hardness distribution of the coating is still in gradient.H13-TiC gradient composite coatings made by laser cladding have a great potential for applications.
In order to solve the coating's general peeling and cracking problems caused by thermal stress at high temperature,H13-TiC gradient composite coatings were made by laser cladding on the surface of H13 hot-work die steel substrates.Using scanning electron microscope,X-ray diffraction and energy dispersive spectrometry,the microstrueture and morphology,distribution of constituents,hardness and thermal stability were checked.The results show that the coating mainly consists of Fe-Cr,TiC,TiO4 and Fe7C3.Polyhedron and dendritic TiC particles were dispersed in the coating.With the rising of TiC,TiC particles become larger,the hardness of the gradient coating is gradually improved,the dendritic structure in the bonding zone become smaller,and their distribution is in gradient.After heating at high temperature of 600℃ and cooling in the air,the decrease of the hardness is the largest in remehing region among the layers,while the substrate H13 steel is in the second place.On the whole,the hardness distribution of the coating is still in gradient.H13-TiC gradient composite coatings made by laser cladding have a great potential for applications.
2010, 34(3): 331-334.
doi: 10.3969/j.issn.1001-3806.2010.03.013
Abstract:
In order to investigate the tribological performance of laser clad coating on die steel,Fe-based alloy powders were coated on 40Cr steel.The tests were carried out with as laser clad layers as upper samples and GCr15 steel as lower samples by means of HT-500 wear tester.The morphologies of wear scars were observed with optical microscopy,and the wear width and the depth of the samples were measured.With lubricant,when the load was 300g,the friction coefficient and wear rate descended 61% and 98.7% respectively compared with that without lubricant,under the load of 500g,they declined 97.9% and 99.8% respectively.As the tests show,the wear performance with 300g load is better than that with 500g load under dry friction and the laser clad layer is worn out seriously with 500g load.The friction coefficient,wear rate and wear width with lubricant is rather less than that under dry friction with the same load.The wear processes are in steady state under the lubricant condition,without running-in period.
In order to investigate the tribological performance of laser clad coating on die steel,Fe-based alloy powders were coated on 40Cr steel.The tests were carried out with as laser clad layers as upper samples and GCr15 steel as lower samples by means of HT-500 wear tester.The morphologies of wear scars were observed with optical microscopy,and the wear width and the depth of the samples were measured.With lubricant,when the load was 300g,the friction coefficient and wear rate descended 61% and 98.7% respectively compared with that without lubricant,under the load of 500g,they declined 97.9% and 99.8% respectively.As the tests show,the wear performance with 300g load is better than that with 500g load under dry friction and the laser clad layer is worn out seriously with 500g load.The friction coefficient,wear rate and wear width with lubricant is rather less than that under dry friction with the same load.The wear processes are in steady state under the lubricant condition,without running-in period.
2010, 34(3): 335-338.
doi: 10.3969/j.issn.1001-3806.2010.03.014
Abstract:
In order to investigate the availability of multi-pulse video frequency accumulation for the improvement of signalto -noise ratio(SNR)in laser echo probing,based on the statistical property of noise,its basic principle was discussed.The feasibility was confirmed by means of numerical simulation and experiment.Results show that multi-pulse video frequency accumulation can improve the SNR with N(1/2) times in laser echo probing while the number of laser pulse N is small,and that if the number N is larger than a certain value,the relation between SNR and N deviate the N(1/2) exponential law due to the influence of system bandwidth,A/D precision and sampling rate.Those results provide a theoretical and experimental foundation to improve the SNR by pulse cumulation for realizing the detection of laser echo in strong noise.And it has important significance to enhance the detecting capability of laser ranging finder.
In order to investigate the availability of multi-pulse video frequency accumulation for the improvement of signalto -noise ratio(SNR)in laser echo probing,based on the statistical property of noise,its basic principle was discussed.The feasibility was confirmed by means of numerical simulation and experiment.Results show that multi-pulse video frequency accumulation can improve the SNR with N(1/2) times in laser echo probing while the number of laser pulse N is small,and that if the number N is larger than a certain value,the relation between SNR and N deviate the N(1/2) exponential law due to the influence of system bandwidth,A/D precision and sampling rate.Those results provide a theoretical and experimental foundation to improve the SNR by pulse cumulation for realizing the detection of laser echo in strong noise.And it has important significance to enhance the detecting capability of laser ranging finder.
2010, 34(3): 339-342,376.
doi: 10.3969/j.issn.1001-3806.2010.03.015
Abstract:
The research and development of the numerical simulation of fast axial flow CO2 lasers,and the main purposes,methods results and application meanings of the numerical simulation were reviewed.The comparison and analysis of the numerical simulation were made on three points as theory equations,numerical method and computation results.The forms,physical meanings and approximations of theory model were disused,the advantages and disadvantages of different numerical methods were analyzed,and the different computational results about the relation between the parameters and performances of lasers were listed.The latest results showed that the discharge characteristics and laser output were relative with structures of discharge tubes and electrodes,distribution of velocity,temperature,pressure,turbulent status and other parameters.According to the development of fast-axial-flow CO2lasers and the computer technology,the improving direction of the numerical simulation was proposed and the application prospects of modeling results under new computing platform were made for design and optimization of lasers.
The research and development of the numerical simulation of fast axial flow CO2 lasers,and the main purposes,methods results and application meanings of the numerical simulation were reviewed.The comparison and analysis of the numerical simulation were made on three points as theory equations,numerical method and computation results.The forms,physical meanings and approximations of theory model were disused,the advantages and disadvantages of different numerical methods were analyzed,and the different computational results about the relation between the parameters and performances of lasers were listed.The latest results showed that the discharge characteristics and laser output were relative with structures of discharge tubes and electrodes,distribution of velocity,temperature,pressure,turbulent status and other parameters.According to the development of fast-axial-flow CO2lasers and the computer technology,the improving direction of the numerical simulation was proposed and the application prospects of modeling results under new computing platform were made for design and optimization of lasers.
2010, 34(3): 343-346.
doi: 10.3969/j.issn.1001-3806.2010.03.016
Abstract:
In order to study the spectral shift and spectral switch phenomena in the near field and far field of polychromatic Gaussian-Schell model(GSM)beam uniformly,based on the general diffraction integral formula of partially coherent light,the analytical spectral density formula of polyehromatic GSM beam passing though the Young's double slits and ABCD optical system was derived.From the general spectral density formula it can be shown that the Fresnel number varies with the frequency,which is the physical reason of the axial spectral shift of the polychromatie GSM beam.Taking the free space as a typical example of the ABCD optical system,the on-axis spectral shift and spectral switch in the near field and the off-axis spectral shift and spectral switch in the far field were studied numerically by means of the general formula.The result shows that the analytical spectral density formula has some theoretical value in researching spectral shift and spectral switch phenomenon of GSM beam diffracted by Young's double slits.
In order to study the spectral shift and spectral switch phenomena in the near field and far field of polychromatic Gaussian-Schell model(GSM)beam uniformly,based on the general diffraction integral formula of partially coherent light,the analytical spectral density formula of polyehromatic GSM beam passing though the Young's double slits and ABCD optical system was derived.From the general spectral density formula it can be shown that the Fresnel number varies with the frequency,which is the physical reason of the axial spectral shift of the polychromatie GSM beam.Taking the free space as a typical example of the ABCD optical system,the on-axis spectral shift and spectral switch in the near field and the off-axis spectral shift and spectral switch in the far field were studied numerically by means of the general formula.The result shows that the analytical spectral density formula has some theoretical value in researching spectral shift and spectral switch phenomenon of GSM beam diffracted by Young's double slits.
2010, 34(3): 347-350.
doi: 10.3969/j.issn.1001-3806.2010.03.017
Abstract:
In order to study the arts and crafts of stainless steel prepared with femtosecond laser,the technical condition and parametric optimization were studied in detail and applied in micromachining the micro-cantilever.The effect of laser fluence,scanning speed and scan times on the morphology of ablated area and ablation rate were analyzed.High quality micro-cantilevers in micrometer level were fabricated.The research shows that femtosecond laser micromachining is a promising and flexible way in micromachining of micro electromechanical devices.
In order to study the arts and crafts of stainless steel prepared with femtosecond laser,the technical condition and parametric optimization were studied in detail and applied in micromachining the micro-cantilever.The effect of laser fluence,scanning speed and scan times on the morphology of ablated area and ablation rate were analyzed.High quality micro-cantilevers in micrometer level were fabricated.The research shows that femtosecond laser micromachining is a promising and flexible way in micromachining of micro electromechanical devices.
2010, 34(3): 351-353,369.
doi: 10.3969/j.issn.1001-3806.2010.03.018
Abstract:
In order to study the optical parametric characteristics of KTiOAsO4,according to momentum and energy conservation rule and dispersion equation of the crystal,the phase-matching,gain,effective nonlinear coefficient deft,walkoff and accept angle curves were analyzed in theory through numerical simulation.Type-Ⅱ phase-matching of KTiOAsO4 crystal was adopted and the cutting angle θ=90°,the angle φ=0°.In room temperature,the idle wavelength was 3463nm by experiment.The maximum of single pulse energy was more than 22mJ,the pulse width was no more than 35.3ns,the beam divergence was no more than 8.9mrad and the repeating frequency was from 1Hz to 40Hz.The experimental results show that KTiOAsO4 crystal adapts to generate mid-infrared laser,especially to generate high energy and high peak power mid-infrared laser in future.
In order to study the optical parametric characteristics of KTiOAsO4,according to momentum and energy conservation rule and dispersion equation of the crystal,the phase-matching,gain,effective nonlinear coefficient deft,walkoff and accept angle curves were analyzed in theory through numerical simulation.Type-Ⅱ phase-matching of KTiOAsO4 crystal was adopted and the cutting angle θ=90°,the angle φ=0°.In room temperature,the idle wavelength was 3463nm by experiment.The maximum of single pulse energy was more than 22mJ,the pulse width was no more than 35.3ns,the beam divergence was no more than 8.9mrad and the repeating frequency was from 1Hz to 40Hz.The experimental results show that KTiOAsO4 crystal adapts to generate mid-infrared laser,especially to generate high energy and high peak power mid-infrared laser in future.
2010, 34(3): 354-356,388.
doi: 10.3969/j.issn.1001-3806.2010.03.019
Abstract:
In order to study the dynamic characteristics of the vector soliton in a mode-locked fiber laser,the vector soliton and the vector soliton bunches were obtained experimentally via nonlinear polarization rotation mode-locked mechanism.The dynamic characteristics of the vector soliton bunches are related to the pumping power and polarization bias.The higher the pumping power,the more are the pairs of the vector soliton bunch originating from the splitting of the vector soliton.Moreover,the vector soliton bunches show the periodic intensity modulation in the time domain.The periodic intensity modulation for the 4th and 7th vector soliton bunches was observed respectively.Experiment result shows that the output vector-soliton bunches are the inherent characteristics of the nonlinear polarization rotation mode-locked fiber laser.Moreover,the periodic intensity modulation phenomena owe to the periodic polarization modulation of the polarization-dependent isolator in the cavity.
In order to study the dynamic characteristics of the vector soliton in a mode-locked fiber laser,the vector soliton and the vector soliton bunches were obtained experimentally via nonlinear polarization rotation mode-locked mechanism.The dynamic characteristics of the vector soliton bunches are related to the pumping power and polarization bias.The higher the pumping power,the more are the pairs of the vector soliton bunch originating from the splitting of the vector soliton.Moreover,the vector soliton bunches show the periodic intensity modulation in the time domain.The periodic intensity modulation for the 4th and 7th vector soliton bunches was observed respectively.Experiment result shows that the output vector-soliton bunches are the inherent characteristics of the nonlinear polarization rotation mode-locked fiber laser.Moreover,the periodic intensity modulation phenomena owe to the periodic polarization modulation of the polarization-dependent isolator in the cavity.
2010, 34(3): 360-362,366.
doi: 10.3969/j.issn.1001-3806.2010.03.021
Abstract:
In order to overcome the disadvantages of the power system of the intense pulsed light equipment,a "mainsubordinate" capacitive charging power circuit based on the IGBT chopper circuit was designed.The on and off-time of IGBT was controlled with the micro-chip computer to achieve high-speed and controlled charging process.The experiments prove that this circuit is not only safe but also can achieve the electric output power larger than 2kW when the operating voltage is 150V,and the output energy is uniform.The "main-subordinate" capacitive charging power circuit based on the IGBT chopper circuit can be adopted in the power of the intense pulsed light equipment.
In order to overcome the disadvantages of the power system of the intense pulsed light equipment,a "mainsubordinate" capacitive charging power circuit based on the IGBT chopper circuit was designed.The on and off-time of IGBT was controlled with the micro-chip computer to achieve high-speed and controlled charging process.The experiments prove that this circuit is not only safe but also can achieve the electric output power larger than 2kW when the operating voltage is 150V,and the output energy is uniform.The "main-subordinate" capacitive charging power circuit based on the IGBT chopper circuit can be adopted in the power of the intense pulsed light equipment.
2010, 34(3): 363-366.
doi: 10.3969/j.issn.1001-3806.2010.03.022
Abstract:
In order to study the mode and defect mode of electromagnetic wave in a flat-panel doping photonic crystal,the conditions of each electromagnetic wave mode were deduced.The defect modes of TE wave and TM wave were calculated by means of the characteristic matrix method.The new defect mode structure of flat-panel doping photonic crystal was obtained.A conclusion was made that the mode of electromagnetic wave was determined by the quantum number of modes and the defect mode was determined by the quantum number of mode and the thickness of the flat-panel.
In order to study the mode and defect mode of electromagnetic wave in a flat-panel doping photonic crystal,the conditions of each electromagnetic wave mode were deduced.The defect modes of TE wave and TM wave were calculated by means of the characteristic matrix method.The new defect mode structure of flat-panel doping photonic crystal was obtained.A conclusion was made that the mode of electromagnetic wave was determined by the quantum number of modes and the defect mode was determined by the quantum number of mode and the thickness of the flat-panel.
2010, 34(3): 367-369.
doi: 10.3969/j.issn.1001-3806.2010.03.023
Abstract:
The purpose of coupling technology is to couple high-power laser from laser diode to double-clad fiber cladding to get the high pumped power.In order to simplify the fiber angle-polished side-coupling technology,a novel method using CO2 laser to make fused side-coupler for double-clad fiber was introduced.The experimental equipment and making process for such fused side-couplers were introduced.The side coupler,from 105μm/125μm muhimode fiber to 125μm double-clad fiber,was made with a coupling efficiency of 82% by means of this method.These results show that this kind of fused side-coupler can be used in high-power side-pumped double-clad fiber lasers practically.
The purpose of coupling technology is to couple high-power laser from laser diode to double-clad fiber cladding to get the high pumped power.In order to simplify the fiber angle-polished side-coupling technology,a novel method using CO2 laser to make fused side-coupler for double-clad fiber was introduced.The experimental equipment and making process for such fused side-couplers were introduced.The side coupler,from 105μm/125μm muhimode fiber to 125μm double-clad fiber,was made with a coupling efficiency of 82% by means of this method.These results show that this kind of fused side-coupler can be used in high-power side-pumped double-clad fiber lasers practically.
2010, 34(3): 370-372.
doi: 10.3969/j.issn.1001-3806.2010.03.024
Abstract:
In order to study the phase change and luminescence properties of nanocrystalline ZrO2-Al2O3:Dy3+ an determine whether energy transfers between ZrO2-Al2O3 and Dy3+,the nanocrystalllne ZrO2-Al2O3:Dy3+ powders were prepared by means of co-precipitation method.The powders were characterized by X-ray diffraction.As the increasing of the sintering temperature,the crystalline phase was changed.The phase of power was analyzed.The results show ZrO2-Al2O3 were solution at 1100℃ to 1200℃,but ZrO2 and Al2O3 were m a small part of solution at 1300℃.Emission spectra of Dy3+ were observed under the excitation of 353nm.Dy3+-ion emission energy is rich.The emission spectra of the main emission peak are at 483nm and 583nm.Excitation spectra were obtained by monitoring 483nm emission.Because of the excitation spectrum including the absorption from the matrix,the energy transfer between the matrix of ZrO2-Al2O3 and Dy3+ occurred.
In order to study the phase change and luminescence properties of nanocrystalline ZrO2-Al2O3:Dy3+ an determine whether energy transfers between ZrO2-Al2O3 and Dy3+,the nanocrystalllne ZrO2-Al2O3:Dy3+ powders were prepared by means of co-precipitation method.The powders were characterized by X-ray diffraction.As the increasing of the sintering temperature,the crystalline phase was changed.The phase of power was analyzed.The results show ZrO2-Al2O3 were solution at 1100℃ to 1200℃,but ZrO2 and Al2O3 were m a small part of solution at 1300℃.Emission spectra of Dy3+ were observed under the excitation of 353nm.Dy3+-ion emission energy is rich.The emission spectra of the main emission peak are at 483nm and 583nm.Excitation spectra were obtained by monitoring 483nm emission.Because of the excitation spectrum including the absorption from the matrix,the energy transfer between the matrix of ZrO2-Al2O3 and Dy3+ occurred.
2010, 34(3): 373-376.
doi: 10.3969/j.issn.1001-3806.2010.03.025
Abstract:
In order to study characteristics of a backward pumped distributed broadband fiber Raman amplifier,with multisemiconductor laser at wavelength of 1426nm,1440nm,1460nm,1475nm and 1495nm as pump source,signal amplification at bandwidth of 80nm in C+L band was realized and better gain flatness and polarization correlation were obtained.The on-off gain was 10.7dB,gain flatness was 1.5dB,and the maximum noise index was-1.96dB.Experiment results indicated that the pump wavelengths and pump power of the fiber Raman amplifier selected according to the numerical value calculation were reasonable,all technical parameters of the system satisfied requirements of the fiber communication.The resuhs will have very import guidance effect for the development of optic communications.
In order to study characteristics of a backward pumped distributed broadband fiber Raman amplifier,with multisemiconductor laser at wavelength of 1426nm,1440nm,1460nm,1475nm and 1495nm as pump source,signal amplification at bandwidth of 80nm in C+L band was realized and better gain flatness and polarization correlation were obtained.The on-off gain was 10.7dB,gain flatness was 1.5dB,and the maximum noise index was-1.96dB.Experiment results indicated that the pump wavelengths and pump power of the fiber Raman amplifier selected according to the numerical value calculation were reasonable,all technical parameters of the system satisfied requirements of the fiber communication.The resuhs will have very import guidance effect for the development of optic communications.
2010, 34(3): 377-380.
doi: 10.3969/j.issn.1001-3806.2010.03.026
Abstract:
Because of the need for broad bandwidth of optical material in optical communication,tungsten-tellurite glass was prepared by means of solid-phase.Its optical properties and thermal stability were studied.Spectral intensity parameters were calculated based on Judd-Oflet theory.According to the McCumber theory,its emission cross section was simulated with a maximum value of 1.85 ×10-20 cm2 and a maximum full width half maximum of 104nm.The thermal stability of glass was analyzed with a maximum differential thermal temperature ΔT of 131℃(difference between glass transition temperature Tg and crystallization temperature Tx).The results show that the erbium-doped tungsten-tellurite glass is a good material for broad bandwidth amplifiers.
Because of the need for broad bandwidth of optical material in optical communication,tungsten-tellurite glass was prepared by means of solid-phase.Its optical properties and thermal stability were studied.Spectral intensity parameters were calculated based on Judd-Oflet theory.According to the McCumber theory,its emission cross section was simulated with a maximum value of 1.85 ×10-20 cm2 and a maximum full width half maximum of 104nm.The thermal stability of glass was analyzed with a maximum differential thermal temperature ΔT of 131℃(difference between glass transition temperature Tg and crystallization temperature Tx).The results show that the erbium-doped tungsten-tellurite glass is a good material for broad bandwidth amplifiers.
2010, 34(3): 381-384.
doi: 10.3969/j.issn.1001-3806.2010.03.027
Abstract:
In order to study the smog extinction to the laser signal in laser beam fide guidance,the transmitting characteristics,such as absorption,scattering and attenuation,in smog of laser at the wavelength of 1.06μm,1.55μm and 10.6μm were simulated with the method of van de Hulst.It is found that the absorption attenuation becomes smaller for laser at longer wavelength when the complex refractive index is a constant.The peak attenuation becomes smaller with the increase of the virtual refractive index.With the increase of laser wavelength,the position of peak attenuation moves toward the direction along which the radius of smoke or smog increases.The results are important reference for studying laser beam guidance.
In order to study the smog extinction to the laser signal in laser beam fide guidance,the transmitting characteristics,such as absorption,scattering and attenuation,in smog of laser at the wavelength of 1.06μm,1.55μm and 10.6μm were simulated with the method of van de Hulst.It is found that the absorption attenuation becomes smaller for laser at longer wavelength when the complex refractive index is a constant.The peak attenuation becomes smaller with the increase of the virtual refractive index.With the increase of laser wavelength,the position of peak attenuation moves toward the direction along which the radius of smoke or smog increases.The results are important reference for studying laser beam guidance.
2010, 34(3): 385-388.
doi: 10.3969/j.issn.1001-3806.2010.03.028
Abstract:
A novel technique that a high power laser diode is directly coupled to a spade micro-lens multimode fiber was presented to improve the fiber coupling efficiency and alignment tolerance.With the field matching technology,the relationship of coupling efficiency was deduced.The alignment tolerances for axis and obliquity were also discussed.The coupling efficiency reached up to 78.5% in experiments.It is helpful to improve the practicality of spade fiber coupling systems.
A novel technique that a high power laser diode is directly coupled to a spade micro-lens multimode fiber was presented to improve the fiber coupling efficiency and alignment tolerance.With the field matching technology,the relationship of coupling efficiency was deduced.The alignment tolerances for axis and obliquity were also discussed.The coupling efficiency reached up to 78.5% in experiments.It is helpful to improve the practicality of spade fiber coupling systems.
2010, 34(3): 389-391.
doi: 10.3969/j.issn.1001-3806.2010.03.029
Abstract:
In order to reduce the complexity for marking a laser-induced gray image and guarantee the marking speed and marking quality,the gray image is divided into different layers using bit-plane concept in image processing.Different laser energy is used to mark different layers.The gray image is induced by energy overlap from multiple layers.This new method was tested and verified on a galvanometer-type laser marking machine.Large number of experiments were carried out.Compared with the traditional methods,the new method can greatly reduce the complexity of high quality laser-induced gray images and guarantee the marking speed and marking quality.Bit-plane method can also be used to laser-induced color images.It plays a significant role in improving the level of laser-induced image.
In order to reduce the complexity for marking a laser-induced gray image and guarantee the marking speed and marking quality,the gray image is divided into different layers using bit-plane concept in image processing.Different laser energy is used to mark different layers.The gray image is induced by energy overlap from multiple layers.This new method was tested and verified on a galvanometer-type laser marking machine.Large number of experiments were carried out.Compared with the traditional methods,the new method can greatly reduce the complexity of high quality laser-induced gray images and guarantee the marking speed and marking quality.Bit-plane method can also be used to laser-induced color images.It plays a significant role in improving the level of laser-induced image.
2010, 34(3): 392-394.
doi: 10.3969/j.issn.1001-3806.2010.03.030
Abstract:
In order to apply liquid crystal optical elements in high power solid pulsed laser facility,the laser damage on liquid crystal optical elements was studied based on simulation and experiments.The physical mode of laser thermal damage on liquid crystal optical elements was built and temperature distribution was calculated at certain incident laser energy density,the laser damage threshold of the polyimide film and liquid crystal material were measured and the laser damage mechanism and threshold of the liquid crystal optical elements were attained.The results indicate that laser damage on the liquid crystal optical elements mainly origin from the decomposition of liquid crystal material and polyimide film under the laser induced high temperature conditions,the laser damage threshold could be improved through optimizing their structural and physical parameters.
In order to apply liquid crystal optical elements in high power solid pulsed laser facility,the laser damage on liquid crystal optical elements was studied based on simulation and experiments.The physical mode of laser thermal damage on liquid crystal optical elements was built and temperature distribution was calculated at certain incident laser energy density,the laser damage threshold of the polyimide film and liquid crystal material were measured and the laser damage mechanism and threshold of the liquid crystal optical elements were attained.The results indicate that laser damage on the liquid crystal optical elements mainly origin from the decomposition of liquid crystal material and polyimide film under the laser induced high temperature conditions,the laser damage threshold could be improved through optimizing their structural and physical parameters.
2010, 34(3): 395-397.
doi: 10.3969/j.issn.1001-3806.2010.03.031
Abstract:
For the feasibility of metal ion reduction induced by the femtosecond laser two-photon absorption of organic polymer material,the experiments were taken in silver nitrate and polyvinylpyrrolidone film mixture at the ratio of the amount of substance of 1:1.In the developed two-photon fabrication system,a single line with the width of 25μm and a 4mm ×0.4mm plate were fabricated.The X-ray photoelectron spectrum revealed that the main element in the product was silver,and the range of resistivity from 10-3Ω·m to 10-5Ω·m was calculated by measuring the resistance.The result shows that using two-photon induced reduction of metal ions,the reaction region can be controlled well,and it is helpful for the conductive metallic microstructure fabrication.
For the feasibility of metal ion reduction induced by the femtosecond laser two-photon absorption of organic polymer material,the experiments were taken in silver nitrate and polyvinylpyrrolidone film mixture at the ratio of the amount of substance of 1:1.In the developed two-photon fabrication system,a single line with the width of 25μm and a 4mm ×0.4mm plate were fabricated.The X-ray photoelectron spectrum revealed that the main element in the product was silver,and the range of resistivity from 10-3Ω·m to 10-5Ω·m was calculated by measuring the resistance.The result shows that using two-photon induced reduction of metal ions,the reaction region can be controlled well,and it is helpful for the conductive metallic microstructure fabrication.
2010, 34(3): 398-400,404.
doi: 10.3969/j.issn.1001-3806.2010.03.032
Abstract:
In order to learn the propagating characteristics of the photonic crystal with symmetnc double defeets,they were studied by means of transfer matrix.It is found that location of defect layers significantly affects the defect mode.If the number of dielectric layers between the two defect layers is greater than the total number of dielectric layers outside the two defect layers,only one single defect mode exists in the band gap and its transmittance reduces rapidly as the difference between the two numbers increases.However,if the number of dielectric layers between the two defect layers is less than the total number of dielectric layers outside the two defect layers,two defect modes with transmittance of 1 exist in band gap and the distance between the two defect modes increases as the difference of the two numbers increases.The spatial electric field distribution of defect mode was also discussed.In order to effectively enhance the electric field in the defect layers,the double defect layers must be close to the center of photonic crystal.
In order to learn the propagating characteristics of the photonic crystal with symmetnc double defeets,they were studied by means of transfer matrix.It is found that location of defect layers significantly affects the defect mode.If the number of dielectric layers between the two defect layers is greater than the total number of dielectric layers outside the two defect layers,only one single defect mode exists in the band gap and its transmittance reduces rapidly as the difference between the two numbers increases.However,if the number of dielectric layers between the two defect layers is less than the total number of dielectric layers outside the two defect layers,two defect modes with transmittance of 1 exist in band gap and the distance between the two defect modes increases as the difference of the two numbers increases.The spatial electric field distribution of defect mode was also discussed.In order to effectively enhance the electric field in the defect layers,the double defect layers must be close to the center of photonic crystal.
2010, 34(3): 401-404.
doi: 10.3969/j.issn.1001-3806.2010.03.033
Abstract:
For encoding binary images,binary image encryption using logic operations based on interferometer was presented to overcome the shortcomings of the previous binary image eneryption.Firstly,a binary image which carries certain information is chosen as encrypted image.Secondly,a key which is used for decrypting image is obtained using logical relationship between them.Finally,the decrypted image is reconstructed with the principle of optical interference.Computer simulation and optical experiment show that eneryption is very convenient and decryption system is simple.Also,this method can realize multi-authentication,so safety performance is very high.
For encoding binary images,binary image encryption using logic operations based on interferometer was presented to overcome the shortcomings of the previous binary image eneryption.Firstly,a binary image which carries certain information is chosen as encrypted image.Secondly,a key which is used for decrypting image is obtained using logical relationship between them.Finally,the decrypted image is reconstructed with the principle of optical interference.Computer simulation and optical experiment show that eneryption is very convenient and decryption system is simple.Also,this method can realize multi-authentication,so safety performance is very high.
2010, 34(3): 405-408,428.
doi: 10.3969/j.issn.1001-3806.2010.03.034
Abstract:
In order to calculate aberrations rapidly and easily,MATLAB's GUI tools are used to make a program interface.A user interface software for calculating light aberrations is realized according to vector formulae to trace optical path passing through spherical faces,when various parameters are input in the program interface,different kinds of aberrations with different view-field angles and different incident points on the pupil can be got by clicking aberration menus,containing on-axis aberrations,off-axis aberrations of wide beam in the tangential plane and the sagittal plane,and aberrations of sharp beam.The focal distance,the ideal image distance of an optical system and spatial ambiguities in images are also obtained.It can be used as a single interface to calculate all sorts of aberrations.The soft has a simple programming language,fewer programming sentences,less machine time and correct running results.The compiled program can be run independently on any operating system without the MATLAB operating environment.
In order to calculate aberrations rapidly and easily,MATLAB's GUI tools are used to make a program interface.A user interface software for calculating light aberrations is realized according to vector formulae to trace optical path passing through spherical faces,when various parameters are input in the program interface,different kinds of aberrations with different view-field angles and different incident points on the pupil can be got by clicking aberration menus,containing on-axis aberrations,off-axis aberrations of wide beam in the tangential plane and the sagittal plane,and aberrations of sharp beam.The focal distance,the ideal image distance of an optical system and spatial ambiguities in images are also obtained.It can be used as a single interface to calculate all sorts of aberrations.The soft has a simple programming language,fewer programming sentences,less machine time and correct running results.The compiled program can be run independently on any operating system without the MATLAB operating environment.
2010, 34(3): 409-412.
doi: 10.3969/j.issn.1001-3806.2010.03.035
Abstract:
To investigate the influence of the waveform of laser pulses on the characteristics of photoacoustic pulses,based on the theory of thermoelastic mechanism for generation of acoustic waves,the characteristics of acoustic waves induced by triangular laser pulses were analyzed by means of theoretical derivation and numerical simulation.Firstly,the theory of thermoelastic mechanism for generation of a plane acoustic source by laser pulses in liquid was elaborated firstly.The analytic expressions of the acoustic pulses induced by laser pulses at the constraint margin and free margin were deduced when the laser waveform was triangular,and the sections of the photoacoustic pulses were obtained through emulation.Secondly,the waveform of the photoacoustic pulse was simulated.Finally,the photoacoustic conversion efficiency was deduced and the influencing factors were analyzed.And then the conversion efficiency at rigid margin and free margin were solved and compared.The obtained results can supply theoretical instruction for the engineering application of the technique of laser generation of acoustic waves.
To investigate the influence of the waveform of laser pulses on the characteristics of photoacoustic pulses,based on the theory of thermoelastic mechanism for generation of acoustic waves,the characteristics of acoustic waves induced by triangular laser pulses were analyzed by means of theoretical derivation and numerical simulation.Firstly,the theory of thermoelastic mechanism for generation of a plane acoustic source by laser pulses in liquid was elaborated firstly.The analytic expressions of the acoustic pulses induced by laser pulses at the constraint margin and free margin were deduced when the laser waveform was triangular,and the sections of the photoacoustic pulses were obtained through emulation.Secondly,the waveform of the photoacoustic pulse was simulated.Finally,the photoacoustic conversion efficiency was deduced and the influencing factors were analyzed.And then the conversion efficiency at rigid margin and free margin were solved and compared.The obtained results can supply theoretical instruction for the engineering application of the technique of laser generation of acoustic waves.
2010, 34(3): 417-421.
doi: 10.3969/j.issn.1001-3806.2010.03.037
Abstract:
For the purpose of studying the damage and beam quality deterioration caused by the non-absorbing inclusions in the fused silica optics,the scattering and the nonlinear propagation of the light field were simulated by finite difference time domain and split Fourier arithmetic respectively.The simulation shows the voids and zirconia inclusions in radius comparable to the wavelength amplify the electromagnetic field amplitude by about 1.6 and 1.9 and after the nonlinear transportation the modulation increases and the beam splits.The results present that the bulk inclusions could cause damage at the rear surface and deterioration of the beam quality.
For the purpose of studying the damage and beam quality deterioration caused by the non-absorbing inclusions in the fused silica optics,the scattering and the nonlinear propagation of the light field were simulated by finite difference time domain and split Fourier arithmetic respectively.The simulation shows the voids and zirconia inclusions in radius comparable to the wavelength amplify the electromagnetic field amplitude by about 1.6 and 1.9 and after the nonlinear transportation the modulation increases and the beam splits.The results present that the bulk inclusions could cause damage at the rear surface and deterioration of the beam quality.
2010, 34(3): 422-424.
doi: 10.3969/j.issn.1001-3806.2010.03.038
Abstract:
In order to study kinetic energy of accelerated electrons in a laser-driven wakefield,maximum and minimum potential of the wakefield that could determine the maximum kinetic energy of the electrons was found by applying the particle in cell method.The peak and valley potential of the plasma wakefield and its relations to laser pulse length and intensity were discussed.It is shown that the maximum energy of a trapped electron is proportional to the intensity of the laser pulse and it reaches maximum value when the laser pulse length equals to nearly ten times of the wavelength.
In order to study kinetic energy of accelerated electrons in a laser-driven wakefield,maximum and minimum potential of the wakefield that could determine the maximum kinetic energy of the electrons was found by applying the particle in cell method.The peak and valley potential of the plasma wakefield and its relations to laser pulse length and intensity were discussed.It is shown that the maximum energy of a trapped electron is proportional to the intensity of the laser pulse and it reaches maximum value when the laser pulse length equals to nearly ten times of the wavelength.
2010, 34(3): 425-428.
doi: 10.3969/j.issn.1001-3806.2010.03.039
Abstract:
In order to study the supermode noise suppression in a mode-locked fiber laser with composite cavity,an effective structure model of the composite cavity was built based on the transfer function.The characteristic of an active modelocked ring fiber laser with composite cavity was investigated theoretically.The dependence of the effective basic frequency of the composite cavity on the length of two sub-cavities was demonstrated in detail.Setting the RF modulation frequency at 1 GHz,the relation between the supermode noise and parameters of the composite cavity were listed in a table.It was shown that the number of supermodes was reducedhowever,the reduction of overall supermode noise was not remarkable in comparison with the standard single-cavity configuration.The result is helpful for experimental study of supermode noise of active mode-locked ring fiber laser with composite cavity.
In order to study the supermode noise suppression in a mode-locked fiber laser with composite cavity,an effective structure model of the composite cavity was built based on the transfer function.The characteristic of an active modelocked ring fiber laser with composite cavity was investigated theoretically.The dependence of the effective basic frequency of the composite cavity on the length of two sub-cavities was demonstrated in detail.Setting the RF modulation frequency at 1 GHz,the relation between the supermode noise and parameters of the composite cavity were listed in a table.It was shown that the number of supermodes was reducedhowever,the reduction of overall supermode noise was not remarkable in comparison with the standard single-cavity configuration.The result is helpful for experimental study of supermode noise of active mode-locked ring fiber laser with composite cavity.
2010, 34(3): 429-432.
doi: 10.3969/j.issn.1001-3806.2010.03.040
Abstract:
In order to study the twofold properties of broad and narrow filter doped with 1-D photonic crystal,the peak transmissivity and full width at half maximum(FWHM)were calculated based on the transfer matrix.It was found that when the refractive index is increased the narrow band's peak transmissivity is invariable and the FWHM is increased,the broad band's transmissivity of the edge of the peak is increased and the FWHM is decreased.When the extinction coefficient is increased the narrow band's peak is decreased rapidly and the broad band's peak is decreased rapidly before decreased adagio,the FWHM is increased.A valuable conclusion is drawn that the refractive index is choice with different demand of the design of a twofold phonic crystal filter and the absorption of dopant has to be taken into account for the design of the twofold phonic crystal filter.
In order to study the twofold properties of broad and narrow filter doped with 1-D photonic crystal,the peak transmissivity and full width at half maximum(FWHM)were calculated based on the transfer matrix.It was found that when the refractive index is increased the narrow band's peak transmissivity is invariable and the FWHM is increased,the broad band's transmissivity of the edge of the peak is increased and the FWHM is decreased.When the extinction coefficient is increased the narrow band's peak is decreased rapidly and the broad band's peak is decreased rapidly before decreased adagio,the FWHM is increased.A valuable conclusion is drawn that the refractive index is choice with different demand of the design of a twofold phonic crystal filter and the absorption of dopant has to be taken into account for the design of the twofold phonic crystal filter.
