Ferlic Nathaniel A, Avramov-Zamurovic Svetlana, O'Malley Owen, Kelly Thomas, Judd K Peter
J Opt Soc Am A Opt Image Sci Vis. 2024 Jun 1;41(6):B85-B94. doi: 10.1364/JOSAA.520909.
The experimental study of optical turbulence proves difficult due to challenges in generating controllable conditions in a laboratory environment. Confined water tanks that produce Rayleigh-Bénard (RB) convection are one method to generate optical turbulence using a controllable temperature gradient. It is of utmost concern to quantify the properties of the optical turbulence generated for characterization of other optical applications such as imaging, sensing, or communications. In this experimental study a Gaussian beam is propagated through a RB water tank where two intensity measurements are made at the receiver's pupil and focal plane. The pupil and focal plane results include quantification of the intensity fluctuation distribution, scintillation distribution, and refractive index structure constant at various values of the temperature gradient. The angle of arrival fluctuations is also calculated at the focal plane to obtain a second estimate of 2. The pupil plane estimate for 2 using scintillation index and focal plane angle of arrival fluctuations is compared to preliminary predictions of 2 as a function of RB temperature gradient showing 2∼ . The outcomes of the study confirm that the RB process produces intensity fluctuations that follow gamma-gamma and log-normal probability density functions. Estimates of the refractive index structure constant 2 produce the same trends with different magnitudes when measured from the pupil and focal plane.
由于在实验室环境中生成可控条件存在挑战，光学湍流的实验研究颇具难度。产生瑞利 - 贝纳德（RB）对流的受限水箱是利用可控温度梯度生成光学湍流的一种方法。对于为成像、传感或通信等其他光学应用的特性表征而生成的光学湍流，量化其特性至关重要。在本实验研究中，高斯光束穿过RB水箱，在接收器的光瞳和焦平面进行两次强度测量。光瞳和焦平面的测量结果包括在不同温度梯度值下强度波动分布、闪烁分布和折射率结构常数的量化。还在焦平面计算到达角波动，以获得对2的第二个估计值。将利用闪烁指数和焦平面到达角波动得到的光瞳平面2估计值与作为RB温度梯度函数的2初步预测值进行比较，结果表明2∼ 。该研究结果证实，RB过程产生的强度波动遵循伽马 - 伽马和对数正态概率密度函数。从光瞳和焦平面测量的折射率结构常数2的估计值呈现相同趋势，但幅度不同。
