Polarization properties of polarized and partially coherent Electromagnetic Gaussian-Schell model pulse beams on slant path in turbulent atmosphere

This paper is based on the unified theory of coherence and polarization of stochastic electromagnetic beams and the extended Huygens–Fresnel principle, combined with the quadratic approximation of Rytov’s phase structure function and the generalized Stokes parameters. We have derived the novel expressions for the cross-spectral density matrix elements and the degree of cross-polarization of a class of elliptically polarized spatially and spectrally partially coherent Electromagnetic Gaussian-Schell model pulse (EGSMP) beams propagating through atmospheric turbulence along a slant path. Additionally, we calculate and analyze the effects of the turbulent intensity, the initial pulse duration, waist width of the beam, the spatial coherence length and temporal coherence length et al. on the polarization properties of fully polarized and partially coherent EGSMP beams. Finally, a comparison of the impact of those factors on the partially polarization beams is made. The results show that the influences of the turbulent intensity, the initial pulse duration, waist width of the beam, the spatial coherence length and temporal coherence length et al. on the polarization properties of fully polarized and partially coherent EGSMP beams are larger. While the effects of those parameters on the partially polarization and partially coherent EGSMP beams are smaller. It is noted that the results of this paper have established sound theoretical basis on the topic of improving performance of the laser system propagating through the atmospheric turbulence.     

Changes in the statistical properties of stochastic anisotropic electromagnetic beams propagating through the oceanic turbulence

On the basis of the extended Huygens?CFresnel principle, an analytical propagation expression for the elements of the cross-spectral density matrix of a stochastic anisotropic electromagnetic beam through oceanic turbulence is derived. From this formula the spectral density, spectral degree of coherence, spectral degree of polarization, orientation angle and the degree of ellipticity of such a beam on propagation are determined. Some numerical calculations are illustrated relating to the anisotropic electromagnetic Gaussian Schell-model beams propagating through oceanic turbulence. The results indicate that the spectral degree of coherence of stochastic anisotropic electromagnetic beams tends to zero with increasing propagation distance through oceanic turbulence, which is in agreement with results previously reported for turbulent atmosphere. It is also found that the changes in the statistical properties of the anisotropic source on propagation are qualitatively different from those of the isotropic source.     

Changes in the state of polarization of partially coherent flat-topped beam in turbulent atmosphere for different source conditions

The polarization states, i.e. the size, the shape and the orientation of the polarization ellipse of partially coherent flat-topped (PCFT) beams passing through atmospheric turbulence are studied in detail. The effects are studied of different source conditions on the polarization states of a PCFT beam propagating through atmospheric turbulence. Based on the unified theory of the polarization states for random electromagnetic beams, we have established the detailed formula for calculating the change of the polarization states of such beams. The polarization states behavior of PCFT beams passing through atmospheric turbulence for any arbitrary order of a flat-topped beam “N” under different source conditions were investigated.     

Propagation of astigmatic stochastic electromagnetic beams in oceanic turbulence

In this paper, we investigate the characteristics of astigmatic stochastic electromagnetic beams through oceanic turbulence. Taking the electromagnetic Gaussian Schell-model (GSM) beam as an example, the analytic expressions for the spectral density and the spectral degree of polarization of the beam propagating the oceanic turbulence are derived. It is indicated that the spectral density along the z-axis of the GSM beam in the oceanic turbulence is severely influenced by the source correlation properties, as well as by the sea-related parameters. We show that the characteristics of the spectral density along the x-axis, y-axis and z-axis of astigmatic electromagnetic GSM beams passing through the oceanic turbulence are qualitatively different. Furthermore, we find that as the astigmatic coefficient becomes larger, the maximum value of the spectral density along the z-axis increases rapidly and the width of the spectral density becomes shorter rapidly. Finally, the results have shown that different strengths of astigmatism have different effects on the spectral degree of polarization.     

Effect of oceanic turbulence on polarization of stochastic beams

On the basis of the extended Huygens-Fresnel principle and the unified theory of coherence and polarization of light we determine the changes in various polarization properties of stochastic beams propagating through the turbulent clear-water ocean. The ocean-induced fluctuations in the refractive index are described via the recently developed power spectrum which takes into account both temperature and salinity variations. Numerical examples of changes in the spectral density, the degree of polarization and in the polarization ellipse are given for electromagnetic Gaussian Schell-model beams. We demonstrate, in particular, how polarization of the propagating beam is affected by statistical properties of the source and by several parameters of oceanic turbulence. We find that propagation of light beams in the oceanic turbulence resembles that in the atmospheric turbulence qualitatively, however evolution and asymptotic saturation of polarization in the oceanic turbulence occurs at much shorter distances.     

部分相干部分偏振电磁束通过光阑透镜的传输

基于广义斯托克斯参量,推导出了部分相干部分偏振高斯谢尔模型(GSM)电磁柬通过光阑透镜后交叉谱密度矩阵、光强、偏振度、偏振椭圆的方位角及椭偏角的解析表达式,并用以研究菲涅耳数、自相关和互相关长度以及束腰宽度对焦移和偏振特性的影响.对主要数值计算结果做了物理解释.     

部分相干部分偏振电磁束通过光阑透镜的传输

基于广义斯托克斯参量,推导出了部分相干部分偏振高斯谢尔模型(GSM)电磁束通过光阑透镜后交叉谱密度矩阵、光强、偏振度、偏振椭圆的方位角及椭偏角的解析表达式,并用以研究菲涅耳数、自相关和互相关长度以及束腰宽度对焦移和偏振特性的影响。对主要数值计算结果做了物理解释。     

Spectral changes of aberrated stochastic electromagnetic flat-topped beams propagating in turbulent atmosphere

In this paper, taking the electromagnetic partially coherent flat-topped (PCFT) beam as an example, we investigate the spectral changes of stochastic electromagnetic beams with astigmatic aberration propagating through a turbulent atmosphere. The analytic expressions for the spectrum of the beams propagating through the turbulent atmosphere are derived. It is shown that the spectral changes of the electromagnetic PCFT beams in the turbulent atmosphere are closely related with the astigmatism aberration, the strength of atmospheric turbulence, the inner scale of turbulence, the correlation of source and the order of flatness of electromagnetic PCFT beams. It is important to note that the spectral changes of the aberrant electromagnetic PCFT beams are insensitive to the atmospheric turbulence. Some possible explanations have also been given for the interesting physical phenomena.     

Changes in polarization properties of partially polarized,partially coherent vectorial cosh-Gaussian beams propagating in oceanic turbulence

Changes in polarization properties of partially polarized, partially coherent vectorial cosh-Gaussian (ChG) beams propagating in oceanic turbulence are studied with the unified theory of coherence and polarization. Numerical examples of changes in optical intensity and polarization properties such as the degree of polarization, orientation angle, and degree of ellipticity of the beam propagating in the turbulent ocean are given. We find that both parameters of the source and oceanic turbulence have an effect upon the polarization properties of the beam. The degree of polarization fluctuates when the ChG beam propagates in the oceanic turbulence, and it has an obvious reconstruction phenomenon in the far-field zone.     

矩形分布高斯-谢尔模型列阵光束的等效曲率半径

推导出矩形分布高斯-谢尔模型（GSM）列阵光束通过湍流大气传输的等效曲率半径的解析表达式。研究表明,等效曲率半径由湍流强度、GSM列阵光束参数及光束的叠加方式等因素共同确定。湍流使得等效曲率半径减小,但湍流对交叉谱密度函数叠加时等效曲率半径的影响要比光强叠加时大。在自由空间中,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径要比光强叠加时的大。但是,随着湍流的增强,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径可以大于、等于或小于光强叠加时的等效曲率半径。此外,若光束相干参数和子光束数目越大,则等效曲率半径受湍流的影响越大。GSM列阵光束的等效曲率半径受湍流的影响比高斯列阵光束要小。     

矩形分布高斯-谢尔模型列阵光束的等效曲率半径

 推导出矩形分布高斯-谢尔模型（GSM）列阵光束通过湍流大气传输的等效曲率半径的解析表达式。研究表明,等效曲率半径由湍流强度、GSM列阵光束参数及光束的叠加方式等因素共同确定。湍流使得等效曲率半径减小,但湍流对交叉谱密度函数叠加时等效曲率半径的影响要比光强叠加时大。在自由空间中,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径要比光强叠加时的大。但是,随着湍流的增强,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径可以大于、等于或小于光强叠加时的等效曲率半径。此外,若光束相干参数和子光束数目越大,则等效曲率半径受湍流的影响越大。GSM列阵光束的等效曲率半径受湍流的影响比高斯列阵光束要小。     

Changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic Hermite–Gaussian beams in turbulence

The unified theory of coherence and polarization is applied to an investigation of the changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic Hermite–Gaussian (EHG) beams propagating through atmospheric turbulence. Based on the extended Huygens–Fresnel principle, the 2×2 electric cross-spectral density matrix of partially coherent EHG beams in turbulence is expressed analytically by using a quadratic approximation of Rytov's phase structure function. The analytical expressions for the degree of polarization, the degree of coherence and the spectrum of partially coherent EHG beams in turbulence are derived, and the corresponding analytical results of electromagnetic Gaussian Schell-model (EGSM) beams can be obtained when the order number of the Hermite polynomial is zero. Some interesting results are obtained, which are illustrated by using numerical examples.     

Propagation properties of radial partially coherent flat-topped array beams in a turbulent atmosphere

With the help of the tensor method, the analytical expression for the cross-spectral density of the radial partially coherent flat-topped array (RPCFTA) beams propagating in a turbulent atmosphere is derived, where the correlated superposition and uncorrelated superposition are considered. The average intensity, the spatial coherence properties and power in bucket (PIB) of these kinds of beams are investigated in detail. It is shown by numerical results and analysis that the average intensity and the spatial coherence of the correlated or uncorrelated RPCFTA beams will change on propagation and this change is dependent upon the correlation of the source's beamlets and atmospheric turbulence. In addition, the comparisons of the average intensity and the spatial coherence between the correlated and the uncorrelated RPCFTA beams propagating both in turbulent atmosphere and in free space are also given, and some interesting results are obtained. The laser power of focus ability of the single PCFT beam is worse than that of the correlated RPCFTA beam and but better than that of the uncorrelated RPCFTA beam when propagation distance in turbulent atmosphere is far-field plane.     

部分相干Airy光束在湍流大气中传输时的偏振特性

研究了部分相干Airy光束在湍流大气中传输时的偏振特性,偏振保持度作为衡量偏振传输效果的一个重要参数.结果表明:部分相干Airy光束在湍流大气中传输足够远时,其偏振度会变回到初始值;而在自由空间中传输,光束的偏振度会保持在某一个特定值;在湍流大气中,当光束传输距离不是很远时,光束对称轴上的偏振度分布为Airy函数,但是当传输足够远时,该偏振度分布逐渐趋向于类高斯状;光束的束腰半径越大,相干长度越长,越有利于光束传输后偏振的保持;存在一个指数截断因子,使得光束的偏振保持度很差.这些结论对于Airy光束在通信领域中的应用具有重要的意义.     

Effect of cross-polarization of electromagnetic source on the degree of polarization of generated beam

In this paper we study the degree of cross-polarization of a beam-like field whose cross-spectral density matrix is symmetric with respect to the permutation of its spatial arguments. Formulas were derived expressing the degree of cross-polarization in terms of the generalized Stokes parameters. With the help of an uniformly polarized quasi-homogeneous model source, the effect of degree of cross-polarization of a source on the degree of polarization of the radiated beam was demonstrated, that, two sources with same spectral degrees of coherence and polarization but with different degrees of cross-polarization can generate beams that have different spectral degrees of polarization in the far field.     

Intensity distribution for the broadband aberrated partially coherent flat-topped beam propagating through turbulent atmosphere

In this paper, taking the partially coherent flat-topped (PCFT) beam as an example, we investigate the intensity distribution of broadband beams with astigmatic aberration propagating through a turbulent atmosphere. The analytic expressions for the intensity of the beams propagating through the turbulent atmosphere are derived. It is shown that the intensity distribution of the broadband aberrated PCFT beams in the turbulent atmosphere are closely related with the astigmatism aberration, the strength of atmospheric turbulence, the order of flatness, the correlation of source and the bandwidth of PCFT beams. It is important to note that the position of the focal plane of the broadband aberrated (or not) PCFT beams can be modulated by changing the aberration, the order of flatness, the correlation and the bandwidth of PCFT beams.     

直流固态继电器电磁脉冲失效模式实验研究

采用电流注入法对某型直流固态继电器输入端与输出端的电磁脉冲损伤机制及失效模式进行了实验研究,结果表明:输入端注入电磁脉冲信号时,输出端会产生误动作,并可造成输入电路中三极管BE节产生短路损伤,导致输入端施加控制信号时输出端无法导通;输出端注入电磁脉冲信号时,可造成输出电路中MOSFET管的栅极和漏极产生短路损伤,导致输出端短路。     

随机电磁高阶Bessel-Gaussian光束在海洋湍流中的传输特性

利用广义惠更斯-菲涅耳衍射积分公式得到了随机电磁高阶Bessel-Gaussian光束在海洋湍流中传输的交叉谱密度矩阵的一般表达式,通过数值计算主要研究了随机电磁高阶Bessel-Gaussian光束在海洋湍流中传输时其在远场输出面的统计特性的变化,包括归一化光谱强度、光谱偏振度、两点的光谱相干度等.数值模拟结果显示海洋湍流能够对随机电磁高阶Bessel-Gaussian光束的归一化光谱强度分布产生影响,随着传输距离的增加,零阶Bessel-Gaussian光束中心出现凹陷,高阶Bessel-Gaussian光束中心会变平坦继而又凹陷下去,不管零阶还是高阶,当传输距离增加到足够远,光强分布都会演变成最终的类高斯分布.x轴上各点的偏振度改变与相干长度δ_(xx),δ_(yy)以及海洋湍流参数有关.x轴上任意一点和原点这两点的光谱相干度也随x的增加而呈振荡变化,并且海洋的均方温度耗散率χT对光谱相干度有影响.     

Polarization ellipse and Stokes parameters of a stochastic electromagnetic Gaussian Schell-model beam propagating through a polarization grating

An analytical propagation formula for the cross-spectral density matrix of a stochastic electromagnetic Gaussian Schell-model (EGSM) beam after propagating through a polarization grating is derived with the help of a tensor method. The statistics properties, particularly the degree of polarization, polarization ellipse and Stokes parameters, of the EGSM beam on propagation after passing through a polarization grating are studied numerically. Our results clearly show that the statistics properties of the EGSM beam on propagation are closely determined by the initial parameters of the EGSM beam and the parameter of the polarization grating. The polarization grating provides one way for modulating the polarization properties of an EGSM beam.     

Effective Radius of Curvature and Rayleigh Length of Partially-Coherent Array Beams Passing Through Oceanic Turbulence

Based on the spatial power spectrum of the refractive index of ocean water, we derive analytical expressions for the effective radius of curvature and Rayleigh length of partially-coherent Hermite–Gaussian linear array (PCHGA) beams propagating through oceanic turbulence. In addition, we discuss theoretically and analyze numerically the influence of oceanic turbulence and array parameters. The effective radius of curvature and Rayleigh length of PCHGA beams increase with the relative strength of temperature and salinity fluctuations, the rate of dissipation of turbulent kinetic energy per unit mass of fluid, the array beam number, beam order, and relative separation distance, but decrease with the increase in the rate of dissipation of the mean-square temperature. The analysis provided here will help to understand the propagation of array beams through ocean turbulence.