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RSS2004 Vol. 28, No. 6
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2004, 28(6): 561-564.
[Abstract]
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Abstract:
The present status of extreme ultraviolet(EUV) source based on laser induced plasma(LIP) and discharge induced plasma(DIP) is reviewed.The characteristics and the progresses of LIP and DIP are compared.In general, discharge induced pinch plasma is of special interest,for its cost is expected to be much lower than that of LIP.
The present status of extreme ultraviolet(EUV) source based on laser induced plasma(LIP) and discharge induced plasma(DIP) is reviewed.The characteristics and the progresses of LIP and DIP are compared.In general, discharge induced pinch plasma is of special interest,for its cost is expected to be much lower than that of LIP.
2004, 28(6): 565-568.
Abstract:
Ni-Cr powder was mixed into paste with a organic binding agent and then painted onto the surface of cast aluminium alloy ZL108 for laser surface alloying using CO2 laser.With optimum process parameters,the allo yed layer with good metallurgical bonding performance is formed.The microstructu re characteristics of alloyed layer are investigated by using OM,SEM,EDAX and XRD.The results show that the alloyed layer is composed of inter-metallic compo unds of Ni-Al,which is some particles dispersed on the substrate of Al-Si mut ual crystal.The micro-hardness of alloyed layer can reach up to 230HV,which was three times higher than that of the substrate materials.The relative wear resi stance is about two times higher than that of the substrate materials.
Ni-Cr powder was mixed into paste with a organic binding agent and then painted onto the surface of cast aluminium alloy ZL108 for laser surface alloying using CO2 laser.With optimum process parameters,the allo yed layer with good metallurgical bonding performance is formed.The microstructu re characteristics of alloyed layer are investigated by using OM,SEM,EDAX and XRD.The results show that the alloyed layer is composed of inter-metallic compo unds of Ni-Al,which is some particles dispersed on the substrate of Al-Si mut ual crystal.The micro-hardness of alloyed layer can reach up to 230HV,which was three times higher than that of the substrate materials.The relative wear resi stance is about two times higher than that of the substrate materials.
2004, 28(6): 569-571.
Abstract:
This article introduces a new charge and discharge circuit of Ti:sapphire laser power supply for the flash lamp.The capacitor is charged by resonant transformer, and the magnetic pulse compressor (MPC) as a discharge switch instead of thyratron used in Ti:sapphire laser power supply for the flash lamp.The function of the circuit is described.
This article introduces a new charge and discharge circuit of Ti:sapphire laser power supply for the flash lamp.The capacitor is charged by resonant transformer, and the magnetic pulse compressor (MPC) as a discharge switch instead of thyratron used in Ti:sapphire laser power supply for the flash lamp.The function of the circuit is described.
2004, 28(6): 572-574.
Abstract:
The bioceramic coating is fabricaed by laser cladding directly processing the mixed power of CaHPO4·2H2O and CaCO3.It is shown that the microstructure of the coating is the granular HAP distributed in the ov erlapped club-shaped β-Ca2P2O7 and the main phases in the coating are β-Ca2P2O7 and Ca5(PO4)3(OH);there is the bonded structure of the extension growth on plane basis between the substrate and the cladding layer,typical cellular crystals in the middle of the molten layer and equiaxed crystals at the top of the cladding layer.The microstructure evolution is determined by the ratio of temperature gradient and solidification velocity(G/R) produced by laser cladding.
The bioceramic coating is fabricaed by laser cladding directly processing the mixed power of CaHPO4·2H2O and CaCO3.It is shown that the microstructure of the coating is the granular HAP distributed in the ov erlapped club-shaped β-Ca2P2O7 and the main phases in the coating are β-Ca2P2O7 and Ca5(PO4)3(OH);there is the bonded structure of the extension growth on plane basis between the substrate and the cladding layer,typical cellular crystals in the middle of the molten layer and equiaxed crystals at the top of the cladding layer.The microstructure evolution is determined by the ratio of temperature gradient and solidification velocity(G/R) produced by laser cladding.
2004, 28(6): 575-579.
Abstract:
This paper deals with the high power laser slab. The influence of the cooling intensities at its top/bottom sides on its highest temperature and maximum thermal stress has been numerically investigated for the case that its pumped sides are cooled with the conventional technique. The optimization of thermal stress field has been performed. The calculation results show that for any pumped power the highest temperature and maximum thermal stress vary with the heat transfer coefficient of the top/bottom sides and the optimum heat transfer coefficient exists. As compared to the case that the top/bottom surfaces are cooled with the conventional technique,using the optimum heat transfer coefficient maximum thermal stress can decrease 36% and the same effect can be achieved if the top/bottom surface temperature is appropriately controlled.
This paper deals with the high power laser slab. The influence of the cooling intensities at its top/bottom sides on its highest temperature and maximum thermal stress has been numerically investigated for the case that its pumped sides are cooled with the conventional technique. The optimization of thermal stress field has been performed. The calculation results show that for any pumped power the highest temperature and maximum thermal stress vary with the heat transfer coefficient of the top/bottom sides and the optimum heat transfer coefficient exists. As compared to the case that the top/bottom surfaces are cooled with the conventional technique,using the optimum heat transfer coefficient maximum thermal stress can decrease 36% and the same effect can be achieved if the top/bottom surface temperature is appropriately controlled.
2004, 28(6): 580-584.
Abstract:
To investigate the relation between medium chemical construction and stimulated Brillouin scattering(SBS),the influences of medium chemical construction on the characteristics of SBS,such as the polarizability,the electrostriction coefficient,the gain coefficient,the phonon lifetime,the Brillouin frequency shift,the absorption coefficient and the optical breakdown threshold are analyzed.The reason for the different characteristics of medium is discussed.
To investigate the relation between medium chemical construction and stimulated Brillouin scattering(SBS),the influences of medium chemical construction on the characteristics of SBS,such as the polarizability,the electrostriction coefficient,the gain coefficient,the phonon lifetime,the Brillouin frequency shift,the absorption coefficient and the optical breakdown threshold are analyzed.The reason for the different characteristics of medium is discussed.
2004, 28(6): 585-587,590.
Abstract:
BP neutral network is used to improve the dependability and precision of welding line shapes model of pulsed laser welding.According to the example that 10Mn steel plate is welded using pulsed laser welding,a welding line shapes forecasting model is set up.Verification shows forecasting values and factual surveying value are almost identical,and the precision is high.The result shows this model is to be feasible and practicable.
BP neutral network is used to improve the dependability and precision of welding line shapes model of pulsed laser welding.According to the example that 10Mn steel plate is welded using pulsed laser welding,a welding line shapes forecasting model is set up.Verification shows forecasting values and factual surveying value are almost identical,and the precision is high.The result shows this model is to be feasible and practicable.
2004, 28(6): 588-590.
Abstract:
A new method through the solution of algebra equations to reconstruct the three-dimension axial symmetry field is presented,which is simulated by numerical calculation and digital image processing technology.The research show that the average error of reconstruction field less than 1%,the reconstruction field precision is better than that of "annulus reconstruction method" when the field distribution of reconstruction boundary area is bigger than zero.
A new method through the solution of algebra equations to reconstruct the three-dimension axial symmetry field is presented,which is simulated by numerical calculation and digital image processing technology.The research show that the average error of reconstruction field less than 1%,the reconstruction field precision is better than that of "annulus reconstruction method" when the field distribution of reconstruction boundary area is bigger than zero.
2004, 28(6): 591-594.
Abstract:
The problems of the current main methods that prevent laser cladding layer from cracking are pointed out.The same and different perfor mance requirements of alloy powder for laser cladding and thermal spraying are also described.The recent development situation of Fe-based alloy powder for laser cladding has been reviewed and a new design principle concerning the composition and microstructure has been put forward.
The problems of the current main methods that prevent laser cladding layer from cracking are pointed out.The same and different perfor mance requirements of alloy powder for laser cladding and thermal spraying are also described.The recent development situation of Fe-based alloy powder for laser cladding has been reviewed and a new design principle concerning the composition and microstructure has been put forward.
2004, 28(6): 595-597.
Abstract:
In order to adapt to the development of modern manuf ac ture technology,a noncontact integrated optic-electronic sensor is designed.It combines three common methods:micrometer,roughness-meter and profilometer and can measure micro-displacement,roughness and profile at the same time.It uses an adaptive noise compensation system to eliminate the noise,whose accuracy is similar to each existing single function sensor.
In order to adapt to the development of modern manuf ac ture technology,a noncontact integrated optic-electronic sensor is designed.It combines three common methods:micrometer,roughness-meter and profilometer and can measure micro-displacement,roughness and profile at the same time.It uses an adaptive noise compensation system to eliminate the noise,whose accuracy is similar to each existing single function sensor.
2004, 28(6): 598-601.
Abstract:
Temperature change affects the output power of DPL remarkably.A real-time temperature control technique is presented which can keep the laser crystal and Q-switched working at the setting temperature under any environment conditions based on TL494 pulse width modulator used to control the temperature.The technique has been used in Nd:YVO4 LD-pumping laser and got stable output power,which proves it is stable and reliable.
Temperature change affects the output power of DPL remarkably.A real-time temperature control technique is presented which can keep the laser crystal and Q-switched working at the setting temperature under any environment conditions based on TL494 pulse width modulator used to control the temperature.The technique has been used in Nd:YVO4 LD-pumping laser and got stable output power,which proves it is stable and reliable.
2004, 28(6): 602-603.
Abstract:
The technique of capsulotomy for postoperative membrane cataract using Nd:YAG laser after various cataract extraction is studied in order to improve the therapeutic effects.In a postoperative stages ran ging 35 days～8 years,106 eyes with postoperative membrane cataract after various types of surgery were treated with 4mm～4.5mm diameter Nd:YAG laser posterior capsulotomy under dilated pupils.The results as follow:76 eyes (71.69%) were successfully opened with a single shot and 24 eyes(22.64%)op ened with 2～4 times shots.In a follow up ranged from 3 months～2 years,100 eyes(94.33%) were successfully opened on postoperative membrane with the suitable holes through Nd:YAG laser therapy,and the best corrected visual a cuity was improved ranged 0.6～1.5.Other 21 eyes had the corrected visual acuity lower than 1.0 because of the primary eye diseases that existed before the laser treatment.The complications included iris haemorrhage,slight damage on the surface of intraocular lens and breakup of anterior vitreous membrance,but had no in fluence upon the vision.It can be concluded that Nd:YAG laser capsul otomy is a safe and effective technique for postoperative membrane cataract. Handling of the best opportunity,accurate methods, and preventing of complication is the key of improving the effects.
The technique of capsulotomy for postoperative membrane cataract using Nd:YAG laser after various cataract extraction is studied in order to improve the therapeutic effects.In a postoperative stages ran ging 35 days～8 years,106 eyes with postoperative membrane cataract after various types of surgery were treated with 4mm～4.5mm diameter Nd:YAG laser posterior capsulotomy under dilated pupils.The results as follow:76 eyes (71.69%) were successfully opened with a single shot and 24 eyes(22.64%)op ened with 2～4 times shots.In a follow up ranged from 3 months～2 years,100 eyes(94.33%) were successfully opened on postoperative membrane with the suitable holes through Nd:YAG laser therapy,and the best corrected visual a cuity was improved ranged 0.6～1.5.Other 21 eyes had the corrected visual acuity lower than 1.0 because of the primary eye diseases that existed before the laser treatment.The complications included iris haemorrhage,slight damage on the surface of intraocular lens and breakup of anterior vitreous membrance,but had no in fluence upon the vision.It can be concluded that Nd:YAG laser capsul otomy is a safe and effective technique for postoperative membrane cataract. Handling of the best opportunity,accurate methods, and preventing of complication is the key of improving the effects.
2004, 28(6): 604-608.
Abstract:
The new developments of optical waveguide amplifier are summarized.Amplifiers with different structures,different fabricating methods and different material are described.
The new developments of optical waveguide amplifier are summarized.Amplifiers with different structures,different fabricating methods and different material are described.
2004, 28(6): 609-612.
Abstract:
Laser induced ultrasonic waves in coating-substrate systems are broadband and dispersive,and multiple propagation modes overlap in time domain.By using time-frequency analysis based on the Wigner-Ville distribution,the characters of modes and energy distribution are obtained after analyzing laser ultrasound signals in the coating-substrate system,which are obtained by means of the finite element method.Furthermore,time-frequency method provides a direct measurement velocity dispersion by delay estimation,whose advantage is that it only needs a single measured signal.
Laser induced ultrasonic waves in coating-substrate systems are broadband and dispersive,and multiple propagation modes overlap in time domain.By using time-frequency analysis based on the Wigner-Ville distribution,the characters of modes and energy distribution are obtained after analyzing laser ultrasound signals in the coating-substrate system,which are obtained by means of the finite element method.Furthermore,time-frequency method provides a direct measurement velocity dispersion by delay estimation,whose advantage is that it only needs a single measured signal.
2004, 28(6): 613-615,624.
Abstract:
Artificial beacon is a key issue of adaptive optical systems.For the air-borne optical systems,artificial beacon is used to sample the wavefront distortion which is mainly caused by the atmospheric turbulence and the change of gravity field and temperature field.A kind of beacon composed of both Rayleigh and sodium guide stars is presented to detect the wave-front.A numerical model is discussed.The corresponding simulation result is given.It is found that the adaptive optics based on the beacon composed of the two kinds of laser guide stars are feasible for the wave-front detection of air-borne optics.
Artificial beacon is a key issue of adaptive optical systems.For the air-borne optical systems,artificial beacon is used to sample the wavefront distortion which is mainly caused by the atmospheric turbulence and the change of gravity field and temperature field.A kind of beacon composed of both Rayleigh and sodium guide stars is presented to detect the wave-front.A numerical model is discussed.The corresponding simulation result is given.It is found that the adaptive optics based on the beacon composed of the two kinds of laser guide stars are feasible for the wave-front detection of air-borne optics.
2004, 28(6): 616-619,629.
Abstract:
Through LD double-end-pumped Nd:YVO4 laser crystal working character analysis,laser crystal thermal model and boundary condition according with practical working condition are built.Laser crystal interior temperature field and end-face thermal distortion field calculation equations are obtained by semi-analytical thermal analysis method,simultaneity all kinds of parameters affecting laser crystal temperature field distribution are all analyzed.All research results can be generalized to other laser crystals,and these research will be theoretically established for further research to effectively resolve laser-diode end-pumped laser system's thermal effect problem.
Through LD double-end-pumped Nd:YVO4 laser crystal working character analysis,laser crystal thermal model and boundary condition according with practical working condition are built.Laser crystal interior temperature field and end-face thermal distortion field calculation equations are obtained by semi-analytical thermal analysis method,simultaneity all kinds of parameters affecting laser crystal temperature field distribution are all analyzed.All research results can be generalized to other laser crystals,and these research will be theoretically established for further research to effectively resolve laser-diode end-pumped laser system's thermal effect problem.
2004, 28(6): 620-624.
Abstract:
Luminescent mechanism of ZnS and the preparation principle of thin film deposited by pulsed lasers and its chararacteristic are summarized.The deposition parameters affecting the quality of the ZnS thin film during pulsed laser deposition are analysed emphatically.The prospect and potential applications of the film are also tentatively discussed.
Luminescent mechanism of ZnS and the preparation principle of thin film deposited by pulsed lasers and its chararacteristic are summarized.The deposition parameters affecting the quality of the ZnS thin film during pulsed laser deposition are analysed emphatically.The prospect and potential applications of the film are also tentatively discussed.
2004, 28(6): 625-629.
Abstract:
Based on the Kirchhoff law,a practical temperature real-time measurement system using laser diode InGaAs/I and LiTaO3 pyroelectric detector is presented.By means of analyzing the relationships among resolving power of A/D converter,temperature measurement sensitivity of V(T)-T curve and temperature measurement range,16bite A/D converter for this instrument is determined.According to the relationships among temperature measurement accuracy,relative temperature measurement sensitivity of V(T)-T curve and waveleng ths,further optimal wavelength is discussed.Based on the relationships among resolving power of the detector and A/D converter and temperature sensitivity of V(T)-T curve,further optimal wavelength bandwidth is analyzed.Temperature measurement sensitivity of the instrument at 673K～1473K is given.Temperature measurement sensitivity is above 0.5K at lower temperatures and above 0.1K at higher temperatures at 673K～1473K after using optimal parameters.Temperature measurement inaccuracy at 673K～1473K exceeds 0.3%.
Based on the Kirchhoff law,a practical temperature real-time measurement system using laser diode InGaAs/I and LiTaO3 pyroelectric detector is presented.By means of analyzing the relationships among resolving power of A/D converter,temperature measurement sensitivity of V(T)-T curve and temperature measurement range,16bite A/D converter for this instrument is determined.According to the relationships among temperature measurement accuracy,relative temperature measurement sensitivity of V(T)-T curve and waveleng ths,further optimal wavelength is discussed.Based on the relationships among resolving power of the detector and A/D converter and temperature sensitivity of V(T)-T curve,further optimal wavelength bandwidth is analyzed.Temperature measurement sensitivity of the instrument at 673K～1473K is given.Temperature measurement sensitivity is above 0.5K at lower temperatures and above 0.1K at higher temperatures at 673K～1473K after using optimal parameters.Temperature measurement inaccuracy at 673K～1473K exceeds 0.3%.
2004, 28(6): 630-632.
Abstract:
A burst traffic model in optical burst switch(OBS) is intruduced for the first time.With this model the performance of LAUC-VF output schedule algorithm in OBS is given.The performances of the algorithm under this burst traffic model and nonburst traffic are compared.The simulation results show that the burst traffic model is more reasonable to some extent.
A burst traffic model in optical burst switch(OBS) is intruduced for the first time.With this model the performance of LAUC-VF output schedule algorithm in OBS is given.The performances of the algorithm under this burst traffic model and nonburst traffic are compared.The simulation results show that the burst traffic model is more reasonable to some extent.
2004, 28(6): 633-635.
Abstract:
The theory of boundary reflection is used for arbitrary dots in the interface of the first and second cladding of double-clad fiber (DCF) to confirm the area where the light source emits the rays that can be absor bed by the RE-doped core.Then the absorption efficiency of the dot will be obtained if this area is compared with the whole area of the first cladding.In order to calculate the whole absorption efficiency of DCF,the absorption efficiency of every dot in the interface of the first and second cladding of DCF should be calculated and synthesized.The conclusions of absorption efficiency of circular DCF and offset DCF completely accord with the results calculated by another ray method.However the process of this method is very handy.
The theory of boundary reflection is used for arbitrary dots in the interface of the first and second cladding of double-clad fiber (DCF) to confirm the area where the light source emits the rays that can be absor bed by the RE-doped core.Then the absorption efficiency of the dot will be obtained if this area is compared with the whole area of the first cladding.In order to calculate the whole absorption efficiency of DCF,the absorption efficiency of every dot in the interface of the first and second cladding of DCF should be calculated and synthesized.The conclusions of absorption efficiency of circular DCF and offset DCF completely accord with the results calculated by another ray method.However the process of this method is very handy.
2004, 28(6): 636-638.
Abstract:
By introducing the wavelength distribution and shift of the gain spectrum of semiconductor light amplifiers(SLA) into the theor etical model that describes the dynamic process of picosecond optical pulses pas sing through the amplifiers,the influence of the wavelength distribution and shift of the gain spectrum on the temporal distribution of amplified pulses is numerically studied. The results reveal that for the input pulses with the same tem poral distribution but different wavelengths passing through the SLA,the output pulses have obvious distinctions in their shapes such as the peak power and the time of the appearance of the peak;under the SLA biased at various currents,the output pulse has obvious differences between including and neglecting the gain shift and wavelength dependence for a input pulse passing through the SLA.
By introducing the wavelength distribution and shift of the gain spectrum of semiconductor light amplifiers(SLA) into the theor etical model that describes the dynamic process of picosecond optical pulses pas sing through the amplifiers,the influence of the wavelength distribution and shift of the gain spectrum on the temporal distribution of amplified pulses is numerically studied. The results reveal that for the input pulses with the same tem poral distribution but different wavelengths passing through the SLA,the output pulses have obvious distinctions in their shapes such as the peak power and the time of the appearance of the peak;under the SLA biased at various currents,the output pulse has obvious differences between including and neglecting the gain shift and wavelength dependence for a input pulse passing through the SLA.
2004, 28(6): 639-640,644.
Abstract:
The relations between circularly polarized light's refractive rate and wavelength are obtained through the theory of rotation.The refractive rate of left and right circularly polarized light in the quartz falls down rapidly under the wavelength of 500nm;the refractive rate of left and right circularly polarized light in the quartz falls down slowly above the wavelength of 500nm;the refractive rate's difference of right and left circularly polarized light approaches zero above the wavelength of 2000nm.
The relations between circularly polarized light's refractive rate and wavelength are obtained through the theory of rotation.The refractive rate of left and right circularly polarized light in the quartz falls down rapidly under the wavelength of 500nm;the refractive rate of left and right circularly polarized light in the quartz falls down slowly above the wavelength of 500nm;the refractive rate's difference of right and left circularly polarized light approaches zero above the wavelength of 2000nm.
2004, 28(6): 641-644.
Abstract:
Optical pattern recognition has extensive actual applications.The usually adopted technology is to detect the correlate intension between detection goal image and standard image.We combine effectively wavelet transform with the joint transform correlator(JTC),and have analyzed how to carry out correlation discrimination with wavelet transform,and dedicated the theoretical method and the structural block diagram that realizes image correlation identification.Finally the wavelet type,wavelet filter approach,wavelet filter perform and so on have been introduced.
Optical pattern recognition has extensive actual applications.The usually adopted technology is to detect the correlate intension between detection goal image and standard image.We combine effectively wavelet transform with the joint transform correlator(JTC),and have analyzed how to carry out correlation discrimination with wavelet transform,and dedicated the theoretical method and the structural block diagram that realizes image correlation identification.Finally the wavelet type,wavelet filter approach,wavelet filter perform and so on have been introduced.
2004, 28(6): 645-647,651.
Abstract:
The stable condition of Z-shaped A-O Q-switched intracavity-frequency-doubled laser is analyzed with the matrix optics.The in fluence of the resonator's length,curvature radii of mirrors and the thermal length of the laser cystal on the system stability is analyzed with numerical calculation.It is proved that the shorter cavity is easier to achieve high output power and high transition efficiency.
The stable condition of Z-shaped A-O Q-switched intracavity-frequency-doubled laser is analyzed with the matrix optics.The in fluence of the resonator's length,curvature radii of mirrors and the thermal length of the laser cystal on the system stability is analyzed with numerical calculation.It is proved that the shorter cavity is easier to achieve high output power and high transition efficiency.
2004, 28(6): 648-651.
Abstract:
Based on the 4×4 second-order moments matrix,the M2 factor and intrinsic astigmatism a of general optical beams a restudied.The analytical expressions for the M2 factor and intrin sic astigmatism a of some typical types of beam,such as the general astigmatic beam,rotationally simple astigmatic beam,aligned simple astigmatic beam and stigmatic beam,are given and analyzed.It is shown that the twist result is an increase of the intrinsic astigmatism,but doesn't affect the M2 factor in general.
Based on the 4×4 second-order moments matrix,the M2 factor and intrinsic astigmatism a of general optical beams a restudied.The analytical expressions for the M2 factor and intrin sic astigmatism a of some typical types of beam,such as the general astigmatic beam,rotationally simple astigmatic beam,aligned simple astigmatic beam and stigmatic beam,are given and analyzed.It is shown that the twist result is an increase of the intrinsic astigmatism,but doesn't affect the M2 factor in general.
2004, 28(6): 652-654.
Abstract:
The direct numerical integration,the complex-Gaussian-function expansion,the matrix approach and the beam mode expansion used to simulate beam propagation through optical systems containing hard-edged apertures are compared. It is shown that the direct numerical integration is a widely applicable method,but is very cumbersome and time-consuming as the number of ape rtures increases. The complex-Gaussian-function expansion provides a useful method for fast simulating the hard-edged diffracted beam propagation in the Fresnel and Fraunhofer regions,and obvious calculation errors exist only in the extreme near field. The matrix representation is applicable to the hard-edged diffracted beam propagation in both Fresnel and Fraunhofer regions,but holds only for rotationally symmetrical optical systems and beams. The beam expansion method is suited to approximate the weakly truncated beams in the far field.
The direct numerical integration,the complex-Gaussian-function expansion,the matrix approach and the beam mode expansion used to simulate beam propagation through optical systems containing hard-edged apertures are compared. It is shown that the direct numerical integration is a widely applicable method,but is very cumbersome and time-consuming as the number of ape rtures increases. The complex-Gaussian-function expansion provides a useful method for fast simulating the hard-edged diffracted beam propagation in the Fresnel and Fraunhofer regions,and obvious calculation errors exist only in the extreme near field. The matrix representation is applicable to the hard-edged diffracted beam propagation in both Fresnel and Fraunhofer regions,but holds only for rotationally symmetrical optical systems and beams. The beam expansion method is suited to approximate the weakly truncated beams in the far field.
2004, 28(6): 655-657.
Abstract:
In the inertial confinement fusion (ICF),to achieve optimum fuel compression,the laser beams must irradiate the target uniformly,requiring excellent beam quality.In this paper,using the modeling of transient stimulated rotational Raman scattering (SRRS),the SRRS of high-power ultraviolet laser beams in long air path has been studied.The threshold condition for the SRRS,the effect of diffraction and hot spots on laser beam quality has been anal yzed.As a result,the effect of diffraction on threshold is very small,but it makes the beam quality decrease.The hot spots not only decrease the threshold con dition but also drop the beam quality.
In the inertial confinement fusion (ICF),to achieve optimum fuel compression,the laser beams must irradiate the target uniformly,requiring excellent beam quality.In this paper,using the modeling of transient stimulated rotational Raman scattering (SRRS),the SRRS of high-power ultraviolet laser beams in long air path has been studied.The threshold condition for the SRRS,the effect of diffraction and hot spots on laser beam quality has been anal yzed.As a result,the effect of diffraction on threshold is very small,but it makes the beam quality decrease.The hot spots not only decrease the threshold con dition but also drop the beam quality.
2004, 28(6): 658-660.
Abstract:
According to the differential equation of light and the characteristic that the GRIN(graded-index) medium can focus the light beam automatically,we have designed the GRIN medium stick array to collimate the laser-diode light beams. The data of computer simulation indicate that the collimation system will work well as planed and the result of collimation can reach as much as 3mrad～4mrad.
According to the differential equation of light and the characteristic that the GRIN(graded-index) medium can focus the light beam automatically,we have designed the GRIN medium stick array to collimate the laser-diode light beams. The data of computer simulation indicate that the collimation system will work well as planed and the result of collimation can reach as much as 3mrad～4mrad.
2004, 28(6): 661-663.
Abstract:
The expression of the far-field light intensity of LD (laser diode) at any spatial location is deduced with Fourier transformation and conversion of coordinates.On this basis,the far-field light intensity distribution is analyzed while the posture of LD relative to origin O has rotated or translated.The theoretical basis has been provided for the testing of parameters like disperse angle and distribution of light intensity etc.of LD.
The expression of the far-field light intensity of LD (laser diode) at any spatial location is deduced with Fourier transformation and conversion of coordinates.On this basis,the far-field light intensity distribution is analyzed while the posture of LD relative to origin O has rotated or translated.The theoretical basis has been provided for the testing of parameters like disperse angle and distribution of light intensity etc.of LD.
2004, 28(6): 664-666.
Abstract:
As to the nonlinear optical equations,the exact analytical solutions can only be available on the condition that the refractive index of the medium is axial symmetry with the paraxial approximation.Beyond these con ditions,the analysis of the equations should resort to computer simulations.The traditional simulation based on Taylor series is a very intricate method consuming a great number of time.However,by introducing new proper variables,the Runge-Kutta method is an economic method on this problem.In this method,the calculations related to the refractive index on either side of the optical planes are greatly simplified.The Runge-Kutta method is introduced and the comparisons between these two methods are also presented.
As to the nonlinear optical equations,the exact analytical solutions can only be available on the condition that the refractive index of the medium is axial symmetry with the paraxial approximation.Beyond these con ditions,the analysis of the equations should resort to computer simulations.The traditional simulation based on Taylor series is a very intricate method consuming a great number of time.However,by introducing new proper variables,the Runge-Kutta method is an economic method on this problem.In this method,the calculations related to the refractive index on either side of the optical planes are greatly simplified.The Runge-Kutta method is introduced and the comparisons between these two methods are also presented.
2004, 28(6): 667-669,672.
Abstract:
In order to analyse testing precision of centrobaric of laser facula,atmosphere transmission,image error of optical system,size of infrared CCD photosensitive cell and relative measuring position are studied.The analytical results provide academic reference for optimization of the testing system.
In order to analyse testing precision of centrobaric of laser facula,atmosphere transmission,image error of optical system,size of infrared CCD photosensitive cell and relative measuring position are studied.The analytical results provide academic reference for optimization of the testing system.
2004, 28(6): 670-672.
Abstract:
The diffraction of Gaussian beams at an square aperture is studied based on the Kirchhoff and Fresnel diffraction integrals.Detailed numerical results are presented and compared.It is shown that for a given waist width w0(w0≥λ,λ is wavelength),the valid range of the Fresnel diffraction integral depends on the truncation parameter.Otherwise,if the waist width w0 is comparable to or evenless than the wavelength λ,the Kirchhoff diffraction integral should be used.
The diffraction of Gaussian beams at an square aperture is studied based on the Kirchhoff and Fresnel diffraction integrals.Detailed numerical results are presented and compared.It is shown that for a given waist width w0(w0≥λ,λ is wavelength),the valid range of the Fresnel diffraction integral depends on the truncation parameter.Otherwise,if the waist width w0 is comparable to or evenless than the wavelength λ,the Kirchhoff diffraction integral should be used.
