共查询到19条相似文献,搜索用时 125 毫秒
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讨论环形孔径高斯光束的远场光斑能量分布,并给出拟合表达式。首先推导光束没有拌动时远场光斑的光能分布表达式,然后研究各种不同中心遮拦和不同光束截断比。在有以及没有激光束拌动的情况下,对高斯光束的远场环围能量分布变化的影响。 相似文献
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复宗量双曲正弦高斯光束的传输特性 总被引:2,自引:0,他引:2
对复宗量双曲正弦高斯(EshG)光束的一些基本特性进行了研究。由Collins公式出发推导出了光束通过近轴ABCD光学系统传输的场分布函数,根据二阶矩的定义和光束在近轴ABCD光学系统中的传输公式推导出了光束通过近轴ABCD光学系统光斑尺寸的解析表达式。得到了复宗量双曲正弦高斯光束在自由空间传输时束腰宽度和位置的解析表达式以及M2因子的表达式。对光强分布、光斑尺寸、束腰宽度及其位置和M2因子进行了数值计算,并对计算结果作了分析。本文所得结果具有广泛的意义,因为正弦高斯光束、双曲正弦高斯光束和复宗量正弦高斯光束均可视为其特例。 相似文献
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激光光斑能量分布的三维伪彩色可视化方法 总被引:5,自引:0,他引:5
人眼对不同灰度级的分辨能力非常有限,但对色彩却相当敏感,能区分有不同亮度、色度和饱和度的成千上万种颜色。根据人眼视觉的这个特点,提出了一种激光光斑能量分布的三维伪彩色可视化方法。该方法利用伪彩色技术将激光光斑的256级灰度图像变换为连续变化的伪彩色图像,通过空间灰度插值运算将离散的图像数据生成光斑的彩色三维模型,实现激光光斑能量分布结构的三维可视化,以反映光斑不同区域能量分布的相对大小和位置,并可以通过3D坐标变换进一步方便人们从各个角度观察激光的能量分布。这为光束质量的评判提供了重要依据。 相似文献
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本文应用复源球面波理论,将高斯光束场按矢量球波函数展开,对高斯光束入射到单个球形粒子上时的弹性散射问题进行了理论分折。并对球形粒子在波束传播轴上时的远场散射光强角分布进行了数值计算,同时还与平面波散射的结果进行了比较。 相似文献
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本文引入象差函数分析聚焦激光光学系统焦点附近的光强分布。推导出了激光光束平行漂移对聚焦光斑位置影响的公式。分析表明,平行漂移将使聚焦光斑产生纵向焦移和横向焦移,其大小取决于光束平移量ρ_0,球差系数S_1,出瞳半径a以及高斯参考球的半球R_0。 相似文献
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从拉盖尔-高斯涡旋光束表达式出发,基于瑞利衍射理论,通过研究涡旋光束在大气湍流中传输时的旋转相干函数的变化规律,总结了涡旋光束在大气湍流中传输时各轨道角动量之间的串扰情况,使用了拓扑荷数探测概率描述串扰规律,并推导了拓扑荷数探测概率的解析表达式。研究了涡旋光束通过湍流后的拓扑荷数的分布情况,并将结果与涡旋光束通过大气随机相位屏的数值仿真结果进行了对比,给出了理论与仿真的拓扑荷数的探测概率随湍流强度以及初始涡旋光束拓扑荷数大小的关系图对比,验证了推导的拓扑荷数探测概率解析表达式的正确性。通过该表达式可进一步研究大气湍流与涡旋光束相互作用从而影响涡旋光束轨道角动量散射的本质,为涡旋光束的空间光通信中选择合适的拓扑荷数间隔,以及在不同湍流强度下选择合适束腰大小以减少串扰带来的误码率提供了理论依据。 相似文献
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首次提出了菱形形位相元结构的随机位相板,用衍射理论分析了经这种随机位相板变换后的激光在远场的光斑特性。结果表明其能量利用率高于其它随机位相板用面阵CCD记录的远场光斑,经计算机处理后得到的光斑包络与数值计算结果一致。 相似文献
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Annularly apodized beams have been suggested for use in optical storage because of their potential to go beyond the conventional spot size and depth-of-focus limits. One concern for such applications is the effects of small aberrations on beams in which the energy is concentrated in a small annular ring. We present calculations and experimental results that show that annular apodization of a Gaussian beam reduces the sensitivity to defocus as well as balanced spherical and coma aberrations. The sensitivity to astigmatism is increased by a small amount. 相似文献
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Bochum H 《Applied optics》1997,36(15):3349-3356
The theoretical and experimental investigation of field properties of annular waveguide lasers with a Fabry-Perot resonator is presented. Oscillation with high azimuthal mode order leads to an annular intensity distribution in the far field with almost linear dependence of the annular diameter on the mode order. Low-order fields form a distinct focal spot in the far field. A laser device with a discharge area of 6-cm diameter and 53-cm length yields an output power of 600 W. 相似文献
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Abstract A theoretical analysis based on coupled field-matter equations is given to describe the recently observed phenomenon of a central dark spot formation of a Gaussian beam transmitted through an absorbing defocusing liquid medium. We find that such a pattern formation, which is accompanied by normal defocusing rings in the far field, originates from interplay between the wave-front curvature of the Gaussian beam and strong spatial self-phase medulation arising from thermally induced refractive index change in the medium. Results of numerical analysis for a thin medium are shown to be in a good quantitative agreement with our experimental findings. Further, the dark spot formation is also predicted by using a focused Gaussian beam and self-focusing medium. 相似文献
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《Advanced Powder Technology》2023,34(7):104058
The powder distribution and interaction between the laser beam and powder flow affect the deposition quality during the process of laser direct energy deposition with a continuous coaxial nozzle. In this paper, some key analytical formulae related to the laser beam-powder flow interaction are comprehensively deduced and validated. The powder distribution formulae for different regions are first established considering the divergence angles of powder jet. The energy attenuation formulae of laser beam passing through the powder flow are derived considering the change of powder distribution from annular to circular Gaussian modes. The temperature formulae of powder particles passing through the laser beam are derived based on a proposed temperature formula with the solid-liquid phase transition, and the powder temperature is also further analyzed. These formulae are validated by published deposition examples and used to analyze the laser beam-powder flow interaction. 相似文献
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Based on the Fresnel diffraction integral and by introducing a hard-aperture function into a finite sum of complex Gaussian functions, the approximate analytical expression for the near-field spectral intensity distribution of a space-time-dependent Gaussian pulsed beam passing through an annular aperture is derived, which permits us to study the on- and off-axis spectral anomalies that are near phase singularities of the diffracted Gaussian pulsed beam in the near-field. The expressions for a circular black screen and a circular aperture are given as special cases of the general results. The relative spectral shift of a space-time-dependent Gaussian pulsed beam versus the different values of the truncation parameters and the position parameters of observation points are also studied and illustrated with numerical calculations. It is shown that the spectral switch appears near phase singularities in the near-field, and the near-field spectral behavior depends on the truncation parameters, the pulse duration tau, and the position parameter. The results of this work have potential applications in free-space information encoding and transmission. 相似文献
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Log-amplitude and phase fluctuations of higher-order annular laser beams in a turbulent medium 总被引:3,自引:0,他引:3
Baykal Y 《Journal of the Optical Society of America. A, Optics, image science, and vision》2005,22(4):672-679
Log-amplitude and phase-correlation and structure functions of higher-order annular laser beams in a turbulent atmosphere are derived. A higher-order annular beam source is defined as the superposition of two different higher-order Hermite-Gaussian beams. A special case of such an excitation is the annular Gaussian beam in which two beams operate at fundamental modes of different Gaussian beam sizes, yielding a doughnut-shaped (annular) beam when the second beam is subtracted from the first beam. Our formulation utilizes Rytov approximation, which makes it applicable in the weak-turbulence regime, especially for log-amplitude fluctuations. Limiting cases of our formulations correctly match with known higher-order-mode solutions that in turn reduce to the Gaussian-beam-wave (TEM00-mode) results. Our results can be applied to determine the scintillation index and the phase fluctuations in free-space optics links under higher-order annular laser beam excitation. Except for the numerical evaluation of a specific example covering an annular Gaussian beam, the results in general are left in integral form and need to be numerically evaluated in detail to obtain quantitative results. 相似文献
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Fischer DG van Dijk T Visser TD Wolf E 《Journal of the Optical Society of America. A, Optics, image science, and vision》2012,29(1):78-84
The scattering of a partially coherent beam by a deterministic, spherical scatterer is studied. In particular, the Mie scattering by a Gaussian Schell-model beam is analyzed. Expressions are derived for (a) the extinguished power, (b) the radiant intensity of the scattered field, and (c) the encircled energy in the far field. It is found that the radiant intensity and the encircled energy in the far field depend on the degree of coherence of the incident beam, whereas the extinguished power does not. 相似文献
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Hayes RR 《Applied optics》1997,36(30):8063-8068
The narrow beam widths associated with intersatellite optical communication links make such links susceptible to signal fading because of pointing jitter. Such fading can be aggravated by stationary offsets in pointing. We calculated the fade rates for the case of two spaceborne telescopes having Gaussian beam profiles, a pointing offset, and pointing jitter that can be described by Gaussian statistics. An integral solution is derived for the general case of a nonsymmetrical system, with and without pointing bias, and closed-form solutions are presented for the case of a symmetrical system (identical platforms and optics). These results show that, for a system with 3-dB margin, the rms pointing jitter must be held to less than 7% of the full beam width to keep the fade rate below once per year. 相似文献
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The far-field anomalous spectral behaviours of a space–time-dependent Gaussian pulsed beam passing through a rectangular aperture are studied. By expanding a hard aperture function into a finite sum of complex Gaussian functions and starting from the Fresnel diffraction integral, the approximate analytical expression for the spectral intensity of a space–time-dependent Gaussian pulsed beam passing through a rectangular aperture is derived. Meanwhile, the corresponding closed-forms for the slit and the unapertured cases are also given as special cases of the general results. The red and blue shifts and the spectral intensity distribution are studied and illustrated with numerical calculations. Specifically, it is shown that the spectral switch takes place when the truncation parameter is equal to particular values or the observation position is at the critical diffraction angle. The possibility of tunable spectral switching in the far field with an apertured pulsed beam by varying the size of the rectangular aperture is highlighted. 相似文献