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RSS2001 Vol. 25, No. 5
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2001, 25(5): 321-328.
[Abstract]
[PDF 1091KB]
Abstract:
The devveloping strategy and high-level roadmap of American high-energy laser weapons is first described in the paper.Then the significant progress of various laser weapons,such as war-zone airborne laser weapons,tactical high-energy laser weapons,space-based laser weapons,ground-based laser weapons and shipborne laser weapons is reviewed.Finally,the technical challenges and possible measures are discussed and analyzed.
The devveloping strategy and high-level roadmap of American high-energy laser weapons is first described in the paper.Then the significant progress of various laser weapons,such as war-zone airborne laser weapons,tactical high-energy laser weapons,space-based laser weapons,ground-based laser weapons and shipborne laser weapons is reviewed.Finally,the technical challenges and possible measures are discussed and analyzed.
2001, 25(5): 328-330.
Abstract:
The theory of ellipsometry is obtained through the composition of two polarized beams.Then the method for phase retardation measurement with λ/4 wave-plate is obtained.
The theory of ellipsometry is obtained through the composition of two polarized beams.Then the method for phase retardation measurement with λ/4 wave-plate is obtained.
2001, 25(5): 331-334.
Abstract:
Based on the thermal mechanism of laser ignition, a one dimension finite difference model has been developed to model the process of laser ignition.The laser ignition characters of B/KNO3/bakelite has also been simulated. Results show that with laser energy, laser power, laser energy density or laser absorption coefficient increasing, ignition delay time is prolonged,variation curve of surface temperature of the powder appears double peaks with laser energy approaching ignition energy threshold,and that ignition power threshold increases with beam semidiameter augmenting, while reduces with laser pulse augmenting. Simulation results are accord with actual rules of laser ignition and experimental outcomes on the whole.
Based on the thermal mechanism of laser ignition, a one dimension finite difference model has been developed to model the process of laser ignition.The laser ignition characters of B/KNO3/bakelite has also been simulated. Results show that with laser energy, laser power, laser energy density or laser absorption coefficient increasing, ignition delay time is prolonged,variation curve of surface temperature of the powder appears double peaks with laser energy approaching ignition energy threshold,and that ignition power threshold increases with beam semidiameter augmenting, while reduces with laser pulse augmenting. Simulation results are accord with actual rules of laser ignition and experimental outcomes on the whole.
2001, 25(5): 335-337.
Abstract:
On the basis of analyzing far-field intensity distribution of pane-waves diffracted by a rectangular annular aperture, a detailed study of the beam quality has been made. Numerical calculation results have been illustrated. The results indicate that it is suitable to characterizing beam quality of this type of annular beams with power in bucket (PIB),β parameter and η parameter.On the other hand,the weakness of these methods has also pointed out.
On the basis of analyzing far-field intensity distribution of pane-waves diffracted by a rectangular annular aperture, a detailed study of the beam quality has been made. Numerical calculation results have been illustrated. The results indicate that it is suitable to characterizing beam quality of this type of annular beams with power in bucket (PIB),β parameter and η parameter.On the other hand,the weakness of these methods has also pointed out.
2001, 25(5): 338-343.
Abstract:
A digital angle measurement technique based on Michelson interferometer is introduced in the paper.Through changing the angular displacement into linear displacement,using special circuits to subdivide and measure the interference pattern,exact measurement for a big angle is realized.Compared with other similar measuring system,this system can be applied to wider-angle measurement with high accuracy.The principle of the system,some special notes and error analysis have been introduced.
A digital angle measurement technique based on Michelson interferometer is introduced in the paper.Through changing the angular displacement into linear displacement,using special circuits to subdivide and measure the interference pattern,exact measurement for a big angle is realized.Compared with other similar measuring system,this system can be applied to wider-angle measurement with high accuracy.The principle of the system,some special notes and error analysis have been introduced.
2001, 25(5): 343-346.
Abstract:
NiCrBSi-TiC and Ti-TiC metal-ceramic composite coatings have been respectively cladded on the surface of TC4 alloys by laser.The microstructure and microhardness of coating has been analyzed.The results show that the NiCrBSi-TiC coating is consisted of γ-Ni primary dendrites,γ-Ni and Ni3B,M23(CB)6,CrB eutectics and TiC particles uniformly distributing in the substrate. Partial dissolution or melting appearing on the edges of TiC particles in the cladding process is observed. While in the Ti-TiC coating,total dissolution melting of TiC particles and their regrowth in the form of dendrites during cooling are found. The microhardness of NiCrBSi-TiC coating (HV900～1200) is distinctly higher than that of Ti-TiC coating (HV600～700).
NiCrBSi-TiC and Ti-TiC metal-ceramic composite coatings have been respectively cladded on the surface of TC4 alloys by laser.The microstructure and microhardness of coating has been analyzed.The results show that the NiCrBSi-TiC coating is consisted of γ-Ni primary dendrites,γ-Ni and Ni3B,M23(CB)6,CrB eutectics and TiC particles uniformly distributing in the substrate. Partial dissolution or melting appearing on the edges of TiC particles in the cladding process is observed. While in the Ti-TiC coating,total dissolution melting of TiC particles and their regrowth in the form of dendrites during cooling are found. The microhardness of NiCrBSi-TiC coating (HV900～1200) is distinctly higher than that of Ti-TiC coating (HV600～700).
2001, 25(5): 347-350.
Abstract:
The effect of outer magnetic field on the penetration depth during the process of laser beam welding has been studied. The results show that there is an optimal value of the outer magnetic field when the weld penetration depth reaches its maximum value.The penetration depth decreases obviously as the outer magnetic field is excessively strong or weak.
The effect of outer magnetic field on the penetration depth during the process of laser beam welding has been studied. The results show that there is an optimal value of the outer magnetic field when the weld penetration depth reaches its maximum value.The penetration depth decreases obviously as the outer magnetic field is excessively strong or weak.
2001, 25(5): 351-355.
Abstract:
Based on the generalized Huygens-Fresnel diffraction integral,the transformation properties of Gaussian beams passing a titled lens are studied.A closed-form propagation equation is derived and some useful results are obtained.A comparison of tilted-axis Gaussian beams with off-axis Gaussian beams is mode.The beam quality of tilted-axis Gaussian beams is analyzed in terms of M2 factor and the power in the bucket.
Based on the generalized Huygens-Fresnel diffraction integral,the transformation properties of Gaussian beams passing a titled lens are studied.A closed-form propagation equation is derived and some useful results are obtained.A comparison of tilted-axis Gaussian beams with off-axis Gaussian beams is mode.The beam quality of tilted-axis Gaussian beams is analyzed in terms of M2 factor and the power in the bucket.
2001, 25(5): 356-361.
Abstract:
The method to measure the distribution of particles.size based on FD principle has been applied for a long time.However its results are affected by the limitation of SSPD and the error of inversion method itself.In the paper,the effect of diffration image central framing,the characters of PSD and CCD response property are studied.Then two methods,i.e.the central framing by PSD and RGB equilibrium by CCD for the diffraction image receiving are put forward,which settle the problem of precision of central framing and determination of r and H and meanwhile escape the problem of peak value saturation by a CCD.Finally,a continual distribution I(H) is obtained and the distribution of particles.size n(D) is inverted accurately upon the Shifrin inversion in the measurement.
The method to measure the distribution of particles.size based on FD principle has been applied for a long time.However its results are affected by the limitation of SSPD and the error of inversion method itself.In the paper,the effect of diffration image central framing,the characters of PSD and CCD response property are studied.Then two methods,i.e.the central framing by PSD and RGB equilibrium by CCD for the diffraction image receiving are put forward,which settle the problem of precision of central framing and determination of r and H and meanwhile escape the problem of peak value saturation by a CCD.Finally,a continual distribution I(H) is obtained and the distribution of particles.size n(D) is inverted accurately upon the Shifrin inversion in the measurement.
2001, 25(5): 361-363.
Abstract:
The influence of the nonlinear absorption on the photobleaching of polymer PMMA/DR1 film is studied in this paper. The experimental results show that the photobleaching induced by the two-photon absorption at 1064nm wavelength can make the film's refractive index change, but this change will become saturated with the photobleaching time.
The influence of the nonlinear absorption on the photobleaching of polymer PMMA/DR1 film is studied in this paper. The experimental results show that the photobleaching induced by the two-photon absorption at 1064nm wavelength can make the film's refractive index change, but this change will become saturated with the photobleaching time.
2001, 25(5): 364-367.
Abstract:
In the paper,some important issues while analyzing general astigmatic Gaussian(GAG) beams are stressed on.Then typical numerical examples are given to illustrate the transformation properties of GAG beams,i.e. for GAG beams,the waist is not certainly located at the position corresponding to the infinite curvature radius of the wave-front and there may be several waists even though in free space,which are different from those of conventional stigmatic Gaussian and simple astigmatic Gaussian beams.
In the paper,some important issues while analyzing general astigmatic Gaussian(GAG) beams are stressed on.Then typical numerical examples are given to illustrate the transformation properties of GAG beams,i.e. for GAG beams,the waist is not certainly located at the position corresponding to the infinite curvature radius of the wave-front and there may be several waists even though in free space,which are different from those of conventional stigmatic Gaussian and simple astigmatic Gaussian beams.
2001, 25(5): 368-371.
Abstract:
On the basis of the analysis of various fast Hankel transformation(FHT) algorithms, the quasi-discrete Hankel transformation(QDHT) is chosen to study the beam propagation through multi-pass laser amplifier system containing a spatial filter. Numerical examples show that FHT is a useful fast algorithm to simulate the beam propagation through a large high power laser amplifier system with cylindrical symmetry.
On the basis of the analysis of various fast Hankel transformation(FHT) algorithms, the quasi-discrete Hankel transformation(QDHT) is chosen to study the beam propagation through multi-pass laser amplifier system containing a spatial filter. Numerical examples show that FHT is a useful fast algorithm to simulate the beam propagation through a large high power laser amplifier system with cylindrical symmetry.
2001, 25(5): 372-375.
Abstract:
Based on the second moments method and orthogonal basis mode expansion,analytical expressions for the M2 factor and mode coherence coefficients of cosh-Gaussian beams have been derived, thus analysis of mode correlation and mode structure of cosh-Gaussian beams is available. A simple method has been also proposed to produce cosh-Gaussian beams in the laboratory.
Based on the second moments method and orthogonal basis mode expansion,analytical expressions for the M2 factor and mode coherence coefficients of cosh-Gaussian beams have been derived, thus analysis of mode correlation and mode structure of cosh-Gaussian beams is available. A simple method has been also proposed to produce cosh-Gaussian beams in the laboratory.
2001, 25(5): 376-378.
Abstract:
We are trying to explore a clinical therapy that can increase the cure rate and decrease the recurrent rate of condyloma acuminatum (CA) after laser operation. 45 female patients with CA in genitalia have been treated with OPIN suppository on the basis of laser operation.The results indicate that the cure rate of CA by laser operation in combination with OPIN suppository is much higher than that of simple laser operation (88.00% vs 60.00%, p<0.01),and the recurrent rate obviously decreases (12.00% vs 40.00% p<0.01). No side effect has been found at the stage of treatment. Therefore,laser operation in combination with OPIN suppository is a safe and effective treatment with CA in female genitalia.
We are trying to explore a clinical therapy that can increase the cure rate and decrease the recurrent rate of condyloma acuminatum (CA) after laser operation. 45 female patients with CA in genitalia have been treated with OPIN suppository on the basis of laser operation.The results indicate that the cure rate of CA by laser operation in combination with OPIN suppository is much higher than that of simple laser operation (88.00% vs 60.00%, p<0.01),and the recurrent rate obviously decreases (12.00% vs 40.00% p<0.01). No side effect has been found at the stage of treatment. Therefore,laser operation in combination with OPIN suppository is a safe and effective treatment with CA in female genitalia.
2001, 25(5): 378-381.
Abstract:
In the paper,the character of satellite communication is introduced.Based on calculation and analysis, the performance parameters of high power optical fiber amplifier for transmitter system and optical fiber preamplifier for receiver system of satellite laser communication have been put forward.The experimental layout of high power optical fiber amplifier and low noise figure optical fiber preamplifier is given.
In the paper,the character of satellite communication is introduced.Based on calculation and analysis, the performance parameters of high power optical fiber amplifier for transmitter system and optical fiber preamplifier for receiver system of satellite laser communication have been put forward.The experimental layout of high power optical fiber amplifier and low noise figure optical fiber preamplifier is given.
2001, 25(5): 382-385.
Abstract:
With silicasol,alumina hydrogel,polyethylene glycol,nitric acid,etc,as adhesive agents while catalyst forming,Pt/SnO2 catalyst used in closed CO2 laser is prepared.The effect of adhesive agents on physical characters and activity of catalyst for CO oxidation are investigated.It is concluded that the conversion of CO on the Pt/SnO2 catalyst which is prepared by containing silica-base adhesion agent is 100% at room temperature of -20℃ as well as space velocity of 1×104h-1.The catalyst still has an excellent activity for CO oxidation at -35℃.
With silicasol,alumina hydrogel,polyethylene glycol,nitric acid,etc,as adhesive agents while catalyst forming,Pt/SnO2 catalyst used in closed CO2 laser is prepared.The effect of adhesive agents on physical characters and activity of catalyst for CO oxidation are investigated.It is concluded that the conversion of CO on the Pt/SnO2 catalyst which is prepared by containing silica-base adhesion agent is 100% at room temperature of -20℃ as well as space velocity of 1×104h-1.The catalyst still has an excellent activity for CO oxidation at -35℃.
2001, 25(5): 386-390.
Abstract:
A monitoring method, which can improve the precision of the turning point monitoring approach,is proposed in the paper. This method stops depositing each layer of a film at the point which has different reflectance extreme overshoot so that the structure of the deposited film is similar to the design. It can improve the monitoring precision of a coating with quarterwave or non-quarterwave optical thickness layers.
A monitoring method, which can improve the precision of the turning point monitoring approach,is proposed in the paper. This method stops depositing each layer of a film at the point which has different reflectance extreme overshoot so that the structure of the deposited film is similar to the design. It can improve the monitoring precision of a coating with quarterwave or non-quarterwave optical thickness layers.
2001, 25(5): 390-393.
Abstract:
Five specifications of diamond core drill have been selected as laser welding object.The welding methods and process parameters, such as laser power, welding speed, focused position and assistant gas have been studied.Some practical application results are introduced.
Five specifications of diamond core drill have been selected as laser welding object.The welding methods and process parameters, such as laser power, welding speed, focused position and assistant gas have been studied.Some practical application results are introduced.
2001, 25(5): 394-397.
Abstract:
The range of the included angle and intensity ratio between reference beam and object beam in holography have been studied through observation of the reappear images with different included angle and intensity ratio.Experiments show that the results would be satisfactory as the range of included angle is 0～140°and the intensity ratio is 2:1～120:1.
The range of the included angle and intensity ratio between reference beam and object beam in holography have been studied through observation of the reappear images with different included angle and intensity ratio.Experiments show that the results would be satisfactory as the range of included angle is 0～140°and the intensity ratio is 2:1～120:1.
2001, 25(5): 398-401.
Abstract:
The effect of the width of pass band on the distortion measurement of Q-switched laser pulse is studied theoretically and some regular conclusions are drawn. In addition, the RF excited Q-switched laser pulses are detected by detecting system with a certain width of pass band and the distortion of waveform is observed.The experimental results are consistent with the theoretical results.
The effect of the width of pass band on the distortion measurement of Q-switched laser pulse is studied theoretically and some regular conclusions are drawn. In addition, the RF excited Q-switched laser pulses are detected by detecting system with a certain width of pass band and the distortion of waveform is observed.The experimental results are consistent with the theoretical results.
