Annular Gaussian beams in turbulent media
Annular Gaussian beams in turbulent media
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DOI：
10.1117/12.507774
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发表时间：
2004-01
期刊：
影响因子：
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通讯作者：
Frida Stromqvist Vetelino;L. Andrews
中科院分区：
文献类型：
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作者：
Frida Stromqvist Vetelino;L. Andrews
具有不同辐照度分布的激光束可以具有良好的闪烁和衍射特性，这是光无线通信领域中的重要品质。研究了辐照截面为圆环形的激光束在随机介质（大气）中的传输。环形光束是由不稳定的光学谐振器和扩束器产生的，不稳定的光学谐振器被用作高功率激光器中的谐振腔，扩束器由望远镜组成，其中第二个反射镜阻挡圆形孔径的中心部分。环形光束被建模为两束不同光斑尺寸的准直高斯光束之差。衍射和闪烁特性的环形光束，水平近地面传播（即恒定的折射率结构参数Cn 2），进行了比较，一个准直和一个聚焦高斯光束。利用Rytov近似计算了环形光束和高斯光束在弱湍流大气中的轴上闪烁指数。求解扩展惠更斯-菲涅耳积分，得到平均辐照度，并由此计算半孔径直径中的功率分数。
A laser beam with a different irradiance profile may have favorable scintillation and diffraction characteristics, which are important qualities in the area of optical wireless communication. The propagation in random media (atmosphere) of a laser beam with an annular, donut-shaped, irradiance cross section was examined. Annular beams are created by unstable optical resonators, which are used as resonant cavities in high power lasers, and by beam expanders that consist of telescopes where the second mirror obstruct the central portion of the circular aperture. The annular beam was modeled as the difference of two collimated Gaussian beams, with different spot sizes. Diffraction and scintillation characteristics of the annular beam, for horizontal near ground propagation (i.e. constant refractive-index structure parameter Cn2), were compared to one collimated and one focused Gaussian beam. The Rytov approximation was used to calculate the on-axis scintillation index in weak atmospheric turbulence for both the annular and the Gaussian beams. The extended Huygens-Fresnel integral was solved to obtain the mean irradiance, from which the fraction of power in half aperture diameter was calculated.