The effects of atmospheric turbulence on laser beam propagation in a closed space—An analytic and experimental approach

Kwiecień, Janusz

doi:10.1016/j.optcom.2018.09.022

Cited by 20 publications

(12 citation statements)

References 4 publications

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“…The laboratory experimental setup is presented in Figure 2. The choice of the testbed topology is done based on literature review and additional enhancement have been done using NIR optics, modern instrumentation, customized hardware trigger, and a turbulence generator [1], [10]- [13]. The laser source is a 1064 nm pigtailed DFB laser diode connected to a collimator.…”

Section: Methodsmentioning

confidence: 99%

Characterization of infrared laser beam through atmospheric optical turbulence in laboratory environment

Coronel

Elayoubi

Alahmadi

et al. 2023

Free-Space Laser Communications XXXV

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The atmospheric effects on the propagation of light have been a matter of interest in fields like astronomy, meteorology, and optical communications where phase variations of wavefront have a significant impact in detection systems. The effects of the optical turbulence on the laser beam change from one region to another. This is linked to the atmospheric characteristics of the area (relative humidity, atmospheric pressure, wind, and temperature). Our research center is in a region with harsh atmospheric conditions for optical propagation. For this reason, it is important to measure and replicate these conditions in the laboratory environment. In this work, we present the results of our laboratory experimental setup to characterize infrared beam at 1064-nm using a turbulence chamber designed by our team. In our experimental setup, the transversal windspeed is varied in the turbulence generator chamber, and the beam centroid is measured after 4-m propagation path for different wavelengths and different optical powers. The beam is analyzed before and after the turbulence generation chamber. In this paper, we report our initial results in developing a laboratory experimental setup to emulate Middle East atmospheric conditions and compensate for these effects using an adaptive optics system.

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Section: Methodsmentioning

confidence: 99%

Characterization of infrared laser beam through atmospheric optical turbulence in laboratory environment

Coronel

Elayoubi

Alahmadi

et al. 2023

Free-Space Laser Communications XXXV

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“…where, k = 2π λ is the wave vector. The parameter C 2 n is important since it characterizes the different stages as summarized in [10]. For example, Davis scale presents C 2 n ∼ 10 −18 m −2/3 as a very weak turbulence, C 2 n ∼ 10 −16 m −2/3 as weak turbulence, and C 2 n ∼ 10 −14 m −2/3 as strong turbulence [17], while Wilfter and Dordowa include two stages: C 2 n ∼ 10 −13 m −2/3 as very strong turbulence and C 2 n ∼ 10 −15 m −2/3 as mean turbulence [18].…”

Section: Proposed System Description and Methodsmentioning

confidence: 99%

“…Turbulence theories had helped to study the atmosphere for many years [1][2][3], and different dissertations, research papers, and projects have been proposed [4][5][6][7][8][9][10]. Those works have applied theories to evaluate statistically wavefront distortions and the angle of arrival fluctuations, including an updated study applied in a closed industrial environment, among others.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Characterization Based on Relative Humidity Control at Optical Turbulence Generator

et al. 2019

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In atmospheric turbulence, relative humidity has been almost a negligible variable due to its limited effect, compared with temperature and air velocity, among others. For studying the horizontal path, a laser beam was propagated in a laboratory room, and an Optical Turbulence Generator (OTG) was built and placed along the optical axis. Additionally, there was controlled humidity inside the room and measuring of some physical variables inside the OTG device for determining its effects on the laser beam. The experimental results show the measurements of turbulence parameters C n 2 , l o , and σ I 2 from beam centroids fluctuations, where increases in humidity generated stronger turbulence.

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“…[ [1,2]] ，一直是激光大气工程应用领域的核心问题。大气介质时空分布的不均匀性和各向异性会导致光束质量退化 [3] ，而热晕 [[4-6]] 则是一种由于大气介质对光束能量的吸收而导致的"负透镜效应"。长期以来，研究人员主要采用自适应光学技术 [7] 来抑制大气扰动带来的光束质量退化。然而，受限于系统造价和复杂度，自适应光学技术多应用于天文望远镜和显微成像 [8] 等。近年来，以涡旋光束、贝塞尔光束、艾里光束为代表的空间结构光束 [9] ，因其无衍射、自愈等特性为改善激光大气传输特性提供了新的解决思路和途径。然而，空间结构光束的传输性能随着传输距离的增大也逐步退化。因此，发展抗大气湍流和热晕效应的新型光束及其调控手段仍是研究热点之一。在我们所提出的利用旋转光束缓解大气湍流方案 [10,11] 中，通过使用相位快速旋转的光束，可在湍流特征时间范围内使其遍历大气通道横截面内的非均匀性和各向异性，使激光束的光束质量得到显著提高。这一相位快速旋转的光束可由拓扑荷数不同的涡旋光束经外差干涉产生，其旋转频率与外差频率相同。在泰勒湍流冻结假设 [12] 下，当旋转光束的旋转周期远小于湍流特征时间时可认为大气介旋转光束可由两束具有不同拓扑荷数 l a,b 的涡旋光束经外差干涉产生，经电光调制 [16] 或声光调制 [17] 等调制后，两涡旋光束的中心圆频率分别为 a,b ，则其合成光场可表示为：…”

Section: 引言如何克服大气湍流、热晕等效应引起的光束漂移、扩展和闪烁等现象unclassified

Propagation characteristics of rotating beams under combined effect of atmospheric turbulence and thermal blooming

Zhong¹,

Xiang²,

Zhang³

et al. 2023

Acta Phys. Sin.

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The rotating beam is such a beam that is generated by the heterodyne interference of vortex beams with different topological charges, whose intensity and wavefront rotate rapidly with time. Under Taylor’s frozen air hypothesis, such a rotating beam, whose rotating period is much shorter than the characteristic time of atmospheric turbulence and the thermal blooming, can travel through all the inhomogeneities due to its rapid rotation during its propagation in the air. The rotation can contribute to the smooth of the wavefront distortion caused by the atmospheric turbulence and the thermal blooming, and thus improve the beam quality and reduce the centroid drift of the rotating beam in far field. The physical model of rotating beam is established by the heterodyne interference of two vortex beams. Taking the atmospheric turbulence and the thermal blooming effect into consideration, the propagation model of the rotating beam in the air was established using the Split-Step Fourier Method (SSFM). For simplicity without generality, the influences of the atmospheric turbulence and the thermal blooming effect on the propagation of rotating beam, are both treated as wavefront screen. The difference is that, the wavefront screen of atmospheric turbulence is generated by the Kolmogorov power spectrum, while that of thermal blooming is generated by the fluid mechanics equation. The physical mechanism of how the rotating beam mitigate the atmospheric turbulence and the thermal blooming effect has been analyzed in detail, that is, when the laser beam rotates faster than the airflow, the laser beam can travel all the inhomogeneities and anisotropies of atmosphere in azimuthal direction within the time interval of airflow. After the laser propagates through the frozen air, the total wavefront distortion in the azimuthal direction becomes centrosymmetric with lower PV value, reducing the beam quality degradation. On the basis, the influence of rotation frequency, power ratio of the sub beams, strength of turbulence and thermal blooming on the propagation characteristics of the rotating beam in atmosphere have been analyzed. Within a certain range, as the beam rotation frequency increases, the mitigation effect of the rotating beam on atmospheric turbulence and thermal blooming effects is enhanced. With the increase of turbulence intensity and thermal blooming intensity, the mitigation effect of the rotating beam is weakened but still can maintain well, which can provide reference for the engineering applications of laser beam in atmosphere.

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The effects of atmospheric turbulence on laser beam propagation in a closed space—An analytic and experimental approach

Cited by 20 publications

References 4 publications

Characterization of infrared laser beam through atmospheric optical turbulence in laboratory environment

Characterization of infrared laser beam through atmospheric optical turbulence in laboratory environment

Atmospheric Characterization Based on Relative Humidity Control at Optical Turbulence Generator

Propagation characteristics of rotating beams under combined effect of atmospheric turbulence and thermal blooming

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