• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文会议>Conference on atmospheric propagation of electromagnetic waves III; 20090126-27; San Jose, CA(US) >Effect of beam types on the scintillations: A review
【24h】

Effect of beam types on the scintillations: A review

机译：光束类型对闪烁的影响：综述

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

When different incidences are launched in atmospheric turbulence, it is known that the intensity fluctuations exhibit different characteristics. In this paper we review our work done in the evaluations of the scintillation index of general beam types when such optical beams propagate in horizontal atmospheric links in the weak fluctuations regime. Variation of scintillation indices versus the source and medium parameters are examined for flat-topped-Gaussian, cosh-Gaussian, cos-Gaussian, annular, elliptical Gaussian, circular (i.e., stigmatic) and elliptical (i.e., astigmatic) dark hollow, lowest order Bessel-Gaussian and laser array beams. For flat-topped-Gaussian beam, scintillation is larger than the single Gaussian beam scintillation, when the source sizes are much less than the Fresnel zone but becomes smaller for source sizes much larger than the Fresnel zone. Cosh-Gaussian beam has lower on-axis scintillations at smaller source sizes and longer propagation distances as compared to Gaussian beams where focusing imposes more reduction on the cosh-Gaussian beam scintillations than that of the Gaussian beam. Intensity fluctuations of a cos-Gaussian beam show favorable behaviour against a Gaussian beam at lower propagation lengths. At longer propagation lengths, annular beam becomes advantageous. In focused cases, the scintillation index of annular beam is lower than the scintillation index of Gaussian and cos-Gaussian beams starting at earlier propagation distances. Cos-Gaussian beams are advantages at relatively large source sizes while the reverse is valid for annular beams. Scintillations of a stigmatic or astigmatic dark hollow beam can be smaller when compared to stigmatic or astigmatic Gaussian, annular and flat-topped beams under conditions that are closely related to the beam parameters. Intensity fluctuation of an elliptical Gaussian beam can also be smaller than a circular Gaussian beam depending on the propagation length and the ratio of the beam waist size along the long axis to that along the short axis (i.e., astigmatism). Comparing against the fundamental Gaussian beam on equal source size and equal power basis, it is observed that the scintillation index of the lowest order Bessel-Gaussian beam is lower at large source sizes and large width parameters. However, for excessively large width parameters and beyond certain propagation lengths, the advantage of the lowest order Bessel-Gaussian beam seems to be lost. Compared to Gaussian beam, laser array beam exhibits less scintillations at long propagation ranges and at some midrange radial displacement parameters. When compared among themselves, laser array beams tend to have reduced scintillations for larger number of beamlets, longer wavelengths, midrange radial displacement parameters, intermediate Gaussian source sizes, larger inner scales and smaller outer scales of turbulence. The number of beamlets used does not seem to be so effective in this improvement of the scintillations.
机译：当在大气湍流中引发不同的入射时，已知强度波动表现出不同的特性。在本文中，我们回顾了在弱波动状态下此类光束在水平大气链路中传播时对常规光束类型的闪烁指数进行评估的工作。检查了平顶高斯，cosh-高斯，cos-Gaussian，环形，椭圆形高斯，圆形（即散光）和椭圆形（即散光）暗空心，最低阶的闪烁指数相对于源和介质参数的变化贝塞尔高斯光束和激光阵列光束。对于平顶高斯光束，当光源尺寸远小于菲涅耳区时，闪烁比单个高斯光束闪烁要大，但对于远大于菲涅耳区的光源，则闪烁要小。与高斯光束相比，与高斯光束相比，高斯光束在较小的光源尺寸和更长的传播距离下具有较低的同轴闪烁，其中高斯光束的聚焦比高斯光束的聚焦减少更多。在较低的传播长度下，cos-高斯光束的强度波动显示出对高斯光束的良好行为。在更长的传播长度下，环形束变得有利。在聚焦情况下，环形光束的闪烁指数低于从较早的传播距离开始的高斯光束和cos-高斯光束的闪烁指数。 Cos-Gaussian光束在较大的光源尺寸下具有优势，而反方向对环形光束有效。当在与光束参数密切相关的条件下，与散光或散光的高斯，环形和平顶光束相比，散光或散光的暗空心光束的闪烁可以更小。椭圆高斯光束的强度波动也可以小于圆形高斯光束，这取决于传播长度和沿长轴的束腰尺寸与沿短轴的束腰尺寸之比（即像散）。在相同的光源尺寸和相同的功率基础上，与基本高斯光束比较，可以观察到，在较大的光源尺寸和较大的宽度参数下，最低阶贝塞尔-高斯光束的闪烁指数较低。但是，对于过大的宽度参数和超出某些传播长度的情况，最低阶的贝塞尔-高斯光束的优势似乎丢失了。与高斯光束相比，激光阵列光束在较长的传播范围和某些中程径向位移参数下表现出较少的闪烁。当将它们相互比较时，对于更大数量的子束，更长的波长，中程径向位移参数，中间高斯光源尺寸，更大的内部尺度和较小的湍流外部尺度，激光阵列光束往往具有减少的闪烁。在改进闪烁方面，使用的子束数量似乎并不那么有效。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号