共查询到19条相似文献,搜索用时 78 毫秒
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对Du Fort-Frankel差分格式用于谐振腔模式计算进行简要分析,以该差分格式为基础,提出基于移动矩阵法的非稳腔模式数值计算快速算法.对空腔共焦非稳腔模式进行数值模拟,将计算结果与参考文献进行对比,两者吻合较好.对有源共焦非稳谐振腔内增益区位置对谐振腔输出功率的影响进行数值计算,结果表明:对于采用共焦非稳腔的大功率激光器,当增益体积一定、小信号增益曲线相同时,随着谐振腔内增益区与凹面镜之间的距离的减小,激光器输出功率会有较为明显的提高.数值算例证明了本文方法的正确性和有效性. 相似文献
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首先用几何光学方法分析了虚共焦非稳腔腔镜倾斜引起的准直光线偏离光轴,形成偏斜光线的角度灵敏度和偏斜距离灵敏度同非稳腔放大率m和腔镜倾斜角β之间的关系,然后用C-6程序计算、分析了柱面条状虚共焦非稳腔单镜、双镜反向和同向倾斜三种情况下不同倾斜角对近场相位和远场强度的影响。数值结果表明,镜腔倾斜会使近场相位由均匀分布变成非均匀分布。从布导致远场光束质量变坏。 相似文献
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Output beam drift and deformation in high-power COIL 总被引:1,自引:0,他引:1
During the operation of a chemical oxygen iodine laser (COIL) with an unstable resonator of a large Fresnel number, as the output power increases, an instability of the output laser beam will appear, behaving mainly as far-field beam spot drift and deformation. In order to interpret this phenomenon, thermal expansion analysis on the scraper with finite element analysis method and a simulation of the output beam mode of this kind of laser by the method of Fast Fourier Transform were developed. From the experimental measurement and the calculation, we proposed that the presence of the nonuniform temperature distribution of scraper causes the front surface of the scraper to tilt and bulge due to thermal expansion. As the output power is increasing, all the mirror surfaces, especially the scraper's, will absorb more and more heat, causing thermal expansion of the mirror front surface to occur more seriously, thus resulting in the tilting and deformation of the far-field beam spot. The initial misalignment of the direction is also an important factor leading to the far-field beam spot drift and deformation. 相似文献
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In scalar diffraction theory, Kirchhoff formula, Rayleigh–Sommerfeld formula, and angular spectrum transmission formula are classic formulas that express diffraction correctly. But as complex calculation, Fresnel diffraction integral, which is the paraxial approximate solution to these formulas, is used widely. This paper presents diffraction transfer function corresponding to each classic diffraction formula, gives discussion on methods when using fast Fourier transform to calculate these formulas, derives conditions each formula must meet when it is calculated correctly based on sampling theorem, and finally real examples are finished to certify the results. 相似文献
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With the help of numerical calculations of the finite element method, we simulate the distributions of the temperature in skin after laser irradiation with four wavelengths, 532 nm, 694 nm, 755 nm, and 800 nm, respectively. Combined metabolism of the organism with the traditional Pennes equation, the induced thermal effect in tissue is expressed. The simulated results show that the temperature in the irradiation center decreases as the increase of the wavelength for the same irradiation duration, and the relationships of the distribution of temperature and the wavelength along the radial and longitudinal directions are different. 相似文献
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Measurement of decay time based on FFT 总被引:1,自引:0,他引:1
Weimin Sun Jianzhong Zhang Lei Yu Yang Zhang Yanrong Xiang Libo Yuan Tong Sun K. T. V. Grattan 《Optics & Laser Technology》2004,36(4):323-326
Decay time is an important parameter in fluorescence temperature and pH value measurement. Many approaches are developed based on different principles. The decay acquisition and estimation method is one of them. A novel estimation method is given in this paper, based on the fast Fourier transform (FFT). The decay time can be calculated from the frequent items of the FFT. The advantages of this method include high accuracy, quick processing, independence on base offset etc. A set of experiment results is obtained based on this method. 相似文献