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.     

Propagation of stochastic electromagnetic vortex beams through the turbulent biological tissues

The general analytical expression of the stochastic electromagnetic vortex beams through turbulent biological tissues is derived based on the fractal model. The statistical properties, including the spectral density, the spectral degree of coherence and the spectral degree of polarization are investigated in detail. It can be found that the normalized spectral density of the stochastic electromagnetic vortex beams with higher topological charge is less influenced by turbulence than that with lower topological charge. In addition, the change of the degree of polarization versus propagation distance of the anisotropic vortex beams in biological tissues differs from that of the isotropic vortex beams. The findings might be useful in the investigation of the structures of biological tissues and operation of communication and sensing systems involving biological tissues turbulence channels.     

Modulation in the statistical properties of stochastic electromagnetic beams through an electromagnetic induced transparency atomic vapor

We report analytical expressions for the elements of the 2 × 2 cross-spectral density matrix of a stochastic electromagnetic beam passing through an electromagnetic induced transparency (EIT) atomic vapor. By use of the derived formulas the changes in the spectral density, the spectral degree of coherence, and the spectral degree of polarization of such a beam on propagation can be studied in detail. Numerical examples show that the statistical properties of the stochastic electromagnetic beam can be modulated by the Rabi frequency of the control light when the beam propagates through the EIT atomic vapor.     

高斯光束通过双焦透镜的聚焦特性

 从Collins公式出发,研究了高斯光束通过双焦透镜后的聚焦特性。在无光阑的情况下,给出了轴上光强和x, y方向两束腰及其位置的解析公式。详细的数值计算表明,轴上光强最大点位于其中一个束腰位置附近或者相重合,但始终不能超过透镜较大的焦点。并且,相对束腰的位移随光阑效应的增加而增加。     

环状光束通过像散透镜的变换特性

 基于Tovar提出的平顶多高斯光束模型,给出了环状光束模型。利用广义惠更斯-菲涅耳衍射积分理论,对环状光束通过像散透镜后的传输和聚焦特性进行计算和分析,并讨论了透镜像散对环状光束经透镜变换后对光束质量的影响。研究结果表明:环状光束通过像散透镜后变为非旋转对称光束;聚焦光强随着透镜像散系数的增大而逐渐减弱,聚焦光斑的方位仅由像散系数确定;在光束阶数和入射光波波长一定的情况下,环状光束通过像散透镜的变换特性和光束质量不仅与透镜像散系数有关,还与系统菲涅耳数有关,像散系数增大或菲涅耳数减小时,光束质量变差。     

高斯光束通过双焦透镜的聚焦特性

从Collins公式出发,研究了高斯光束通过双焦透镜后的聚焦特性。在无光阑的情况下,给出了轴上光强和x, y方向两束腰及其位置的解析公式。详细的数值计算表明,轴上光强最大点位于其中一个束腰位置附近或者相重合,但始终不能超过透镜较大的焦点。并且,相对束腰的位移随光阑效应的增加而增加。     

环状光束通过像散透镜的变换特性

基于Tovar提出的平顶多高斯光束模型,给出了环状光束模型。利用广义惠更斯-菲涅耳衍射积分理论,对环状光束通过像散透镜后的传输和聚焦特性进行计算和分析,并讨论了透镜像散对环状光束经透镜变换后对光束质量的影响。研究结果表明:环状光束通过像散透镜后变为非旋转对称光束;聚焦光强随着透镜像散系数的增大而逐渐减弱,聚焦光斑的方位仅由像散系数确定;在光束阶数和入射光波波长一定的情况下,环状光束通过像散透镜的变换特性和光束质量不仅与透镜像散系数有关,还与系统菲涅耳数有关,像散系数增大或菲涅耳数减小时,光束质量变差。     

The propagation properties and kurtosis parametric characteristics of Hermite-cosh-Gaussian beams passing through fractional Fourier transformation systems

Based on the Collins diffraction integral formula and irradiance moments, the propagation properties and kurtosis parametric characteristics of Hermite-cosh-Gaussian (HChG) beams passing through fractional Fourier transformation systems with spherically aberrated lenses are analyzed in detail. The closed-form expressions for the propagation equation and kurtosis parameter of HChG beams passing ideal fractional Fourier transformation systems are also obtained. By using an efficient algorithm some numerical calculations are also performed in this paper. The results show that the spherically aberrated lenses greatly influence on the intensity distribution and kurtosis parameter of HChG beams passage through fractional Fourier transformation systems. The intensity distribution and kurtosis parameter of HChG beams passage through two types of Lohmann's systems with spherically aberrated lenses, respectively, are no longer equal even in the case of the same fractional order and the same spherical aberration coefficients. The fundamental periods of the two types of Lohmann's systems with spherically aberrated lenses are different, 4 for the type I and 2 for the type II. Therefore, the two optical setups for implementing the fractional Fourier transformation are no longer equivalent in the presence of spherically aberrated lenses.     

Polarization properties of stochastic electromagnetic beams

The behavior of the degree of polarization of a Gaussian Schell-model beam propagating in free space is investigated. Contour diagrams for the degree of polarization, and for the spectral density (‘intensity’) of the polarized and the unpolarized portions of the beam are presented.     

Depolarization of beams of relativistic particles passing through bent crystals

It is shown that the characteristic depolarization length of leptons and baryons is much greater than their dechannelization length. This is due to the gyromagnetic ratio close to two for leptons and due to the large rest mass for baryons. Surgut State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 20–23, October, 1999.     

聚丙烯酸酯泡沫密度均匀性的射线检测技术

低密度泡沫材料大多存在一定程度的密度不均匀性，这对其后续使用性能将带来不良影响。文中简述了ICF靶用聚丙烯酸酯泡沫的制备方法，并利用β射线和X射线检测技术，对直径为mm量级的低密度聚丙烯酸酯泡沫柱进行密度分布表征。研究结果表明:泡沫柱沿轴向的密度分布比较均匀，而沿径向呈内低外高分布，形成了明显的密度梯度。实验表明:射线检测技术测量靶用低密度泡沫的方法可基本满足目前的实验要求，但密度分辨率和空间分辨率还有待进一步提高。     

高斯光束通过像散透镜后光束参数的变化

以二阶矩和环围功率作为束宽定义,对高斯光束通过像散透镜后光束参数,包括束宽和远场发散角作了解析和数值研究。结果表明：因像散引入束宽和远场发散角的相对误差与像散因子、瑞利尺寸、透镜焦距有关。对于束宽而言,相对误差还与传输距离z有关。在几何焦面处x和y方向束宽的相对误差相等。     

Effects of coherence on anisotropic electromagnetic Gaussian-Schell model beams on propagation

An analytical formula for the cross-spectral density matrix of the electric field of anisotropic electromagnetic Gaussian-Schell model beams propagating in free space is derived by using a tensor method. The effects of coherence on those beams are studied. It is shown that two anisotropic stochastic electromagnetic beams that propagate from the source plane z=0 into the half-space z>0 may have different beam shapes (i.e., spectral density) and states of polarization in the half-space, even though they have the same beam shape and states of polarization in the source plane. This fact is due to a difference in the coherence properties of the field in the source plane.     

Focusing properties of twisted Gaussian Schell-model beams passing through a system: The aperture lens or the aperture and lens separated

Starting from the propagation law of partially coherent light, the focusing properties of twisted Gaussian Schell-model (TGSM) beams passing through an optical system consisting of an aperture lens or through a system consisting of a separated aperture and lens are studied. The propagation expressions for focused TGSM beams have been derived. Our main attention is focused on the effect of the coherence of partially coherent light, the twist parameter and the distance between the aperture and lens on the focusing properties of TGSM beams. Numerical calculation results are given to illustrate how the coherence of partially coherent light, the twist parameter and the distance between the aperture and lens affect the axial irradiance in the focused field.     

非傍轴双曲余弦-高斯脉冲电磁光束远场特性

利用矢量瑞利-索末菲衍射积分公式,推导出了非傍轴部分空间相干部分光谱相干双曲余弦-高斯(ChG)脉冲电磁光束在自由空间传输时交叉谱密度矩阵的远场解析公式,并用来表示脉冲电磁光束的光谱密度(光强)和偏振度。结果表明,对非傍轴远场部分空间相干部分光谱相干ChG脉冲电磁光束,其非傍轴性主要由参数f, f决定,而离心参数、脉冲宽度和时间相干长度影响其非傍轴行为。非傍轴部分空间相干部分光谱相干高斯-谢尔模型脉冲电磁光束的远场传输可作为特例处理。     

非傍轴双曲余弦-高斯脉冲电磁光束远场特性

利用矢量瑞利-索末菲衍射积分公式,推导出了非傍轴部分空间相干部分光谱相干双曲余弦-高斯(ChG)脉冲电磁光束在自由空间传输时交叉谱密度矩阵的远场解析公式,并用来表示脉冲电磁光束的光谱密度(光强)和偏振度。结果表明,对非傍轴远场部分空间相干部分光谱相干ChG脉冲电磁光束,其非傍轴性主要由参数f, f决定,而离心参数、脉冲宽度和时间相干长度影响其非傍轴行为。非傍轴部分空间相干部分光谱相干高斯-谢尔模型脉冲电磁光束的远场传输可作为特例处理。     

Far-field properties of electromagnetic elliptical Gaussian vortex beams

The explicit far-field expressions for the TE and TM terms and energy flux distributions of electromagnetic elliptical Gaussian vortex beams are derived and their far-field properties including the phase singularities and energy flux distributions of the TE and TM terms and whole beam are studied in detail. It is shown that there exist two edge dislocations. The number and position of edge dislocations and energy flux distributions are dependent on the amplitude ratio and waist width ratio of electromagnetic elliptical Gaussian vortex beams. The analytical results are illustrated numerically.     

高斯-谢尔模型光束通过杨氏双缝衍射后的解析传输公式

 通过将杨氏双缝窗口函数表示为复高斯函数叠加的方法,从Collins公式出发推导出了高斯-谢尔模型(GSM)光束通过杨氏双缝和ABCD光学系统后光强的近似解析表达式。利用该公式作了数值计算,通过与Collins公式计算结果进行比较,确定了该公式的适用范围,研究了相干长度和双缝中心遮拦比对解析公式适用范围的影响,并对该公式的应用前景作了展望。