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A new method of calculating the orbital angular momentum spectra of Laguerre-Gaussian beams in channels with atmospheric turbulence 下载免费PDF全文
Studying orbital angular momentum(OAM) spectra is important for analyzing crosstalk in free-space optical(FSO)communication systems. This work offers a new method of simplifying the expressions for the OAM spectra of Laguerre-Gaussian(LG) beams under both weak/medium and strong atmospheric turbulences. We propose fixing the radius to the extreme point of the intensity distribution, review the expression for the OAM spectrum under weak/medium turbulence,derive the OAM spectrum expression for an LG beam under strong turbulence, and simplify both of them to concise forms.Then, we investigate the accuracy of the simplified expressions through simulations. We find that the simplified expressions permit accurate calculation of the OAM spectrum for large transmitted OAM numbers under any type of turbulence. Finally,we use the simplified expressions to analytically address the broadening of the OAM spectrum caused by atmospheric turbulence. This work should contribute to the concise theoretical derivation of analytical expressions for OAM channel matrices for FSO-OAM communications and the analytical study of the laws governing OAM spectra. 相似文献
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Silicon nanoparticles have attracted great attention in the past decades because of their intriguing physical properties,active surface state, distinctive photoluminescence and biocompatibility. In this review, we present some of the recent progress in preparation methodologies and surface functionalization approaches of silicon nanoparticles. Further, their promising applications in the fields of energy and electronic engineering are introduced. 相似文献
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为了对粗珩阶段缸套内孔表面粗糙度Rk粗糙度集中的Rk、Rpk和Rvk进行预测,进而对粗珩加工参数进行优化,以珩磨压力(P)、珩磨头旋转速度(VR)和往复速度(VRe)为决定因素,Rk粗糙度集为目标响应,进行多目标优化.建立基于广义回归神经网络(Generalized regression neural network, GRNN)与响应曲面法(Response surface methodology,RSM)的粗糙度预测模型,并采用三因素三水平的全因子珩磨试验进行验证,结果表明所建立模型的预测结果与试验结果具有很好的一致性. GRNN预测模型决定系数R2的均值为0.959,RSM多元回归预测模型决定系数R2的均值为0.963,与RSM所建立的多元回归预测模型相比,GRNN预测模型在预测Rk和Rpk时,预测精度更高,预测误差更小,R2分别提高了0.025和0.020,在预测Rvk时RSM多元回归模型更优,R2提高了0.057.进一步结合响应曲面法分析了3个决定因素对粗糙度的影响显著性并进行了排序,对于... 相似文献
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携带轨道角动量的汉克-贝塞尔(Hankel-Bessel,HB)光束具有无衍射和自聚焦特性,用来作为信息传输的载体有望增大信息传输容量.基于Rytov近似理论,推导得到了HB涡旋光束经过海洋水平弱湍流信道后的螺旋相位谱的解析表达式,并利用数值仿真方法研究了海洋湍流参数对轨道角动量模式探测概率的影响.结果表明,海洋湍流导致发射轨道角动量模式的探测概率下降,出现模式串扰和螺旋相位谱扩展.海洋湍流对HB涡旋光束的负面影响随着轨道角动量模式数、传输距离、温度方差耗散率的增加而增强,随湍流动能耗散率的增加而减弱.HB涡旋光束受以盐度波动驱动的海洋湍流的负面影响更大.另外,在弱湍流及几十米传输距离条件下,HB涡旋光束的传输性能要差于最佳束腰大小设置的拉盖尔-高斯涡旋光束.这些结果有望为海洋环境水下光通信链路的实现提供一定的参考价值. 相似文献
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