共查询到20条相似文献,搜索用时 109 毫秒
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高明南娓娜吕宏倪晋平 《光子学报》2013,(9):1107-1112
根据推广的惠更斯-菲涅耳原理和Rytov相位结构函数二次近似,推导出高斯-谢尔模型光束在湍流大气传输中交叉谱密度矩阵的表达式,研究了湍流对椭圆偏振高斯-谢尔模型光束传输中的偏振特性影响,并与部分偏振高斯-谢尔模型光束进行了对比分析.结果表明,相对于部分偏振高斯-谢尔模型光束,椭圆偏振高斯-谢尔模型光束在湍流大气传输中偏振度、方位角以及椭圆度的变化受湍流的影响较小.同时得到椭圆偏振高斯-谢尔模型光束在湍流大气斜程传输中偏振度的变化幅度比部分偏振高斯-谢尔模型光束的小,而方位角和椭圆度的变化幅度比部分偏振高斯-谢尔模型光束的大. 相似文献
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部分相干部分偏振电磁束通过光阑透镜的传输 总被引:2,自引:2,他引:0
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. 相似文献
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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。 相似文献
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被光阑衍射部分偏振高斯-谢尔模型光束的远场特性 总被引:5,自引:0,他引:5
从部分相干光的传输理论出发,采用光束相干-偏振矩阵方法研究了被光阑衍射部分偏振高斯-谢尔模型光束的远场特性,对远场偏振和光强特性作了详细的数值计算和物理分析。研究结果表明,光阑衍射部分偏振高斯-谢尔模型光束的远场特性与光阑截断参量、光的空间相干性和衍射角有关。并与自由空间的传输特性和以前的工作作了比较分析。 相似文献
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根据光束的相干-偏振矩阵理论,应用柯林公式对部分相干光经光阑衍射后的轴向、横向偏振特性从近场区到远场区的演化规律进行了详细的数值计算。经研究表明,由于光阑的衍射效应,使得高斯谢尔模型光束的偏振出现非均匀分布,光束偏振度沿轴向、横向分布出现多峰振荡现象,并且随着光阑截断参数的减小、光束空间相干长度的增大和传输距离的增大,多峰振荡逐渐增强。光束在自由空间沿轴向传输时,在近场区偏振度分布均匀,与源平面相同,随着传输距离的增大和空间相干长度的减小,偏振度沿轴向分布逐渐增大,无振荡现象。 相似文献
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非均匀偏振光束通过环状光阑像散透镜的聚焦特性 总被引:4,自引:3,他引:1
借助于光束相干偏振矩阵和广义惠更斯-菲涅耳衍射积分公式,研究了非均匀偏振(NUP)光束通过环状光阑像散透镜的聚焦特性,并将圆孔光阑作为环状光阑内径为零的特例处理.数值计算结果表明,实际焦点位置、光强和偏振度分布与透镜的像散、环状光阑的菲涅耳数和遮拦比以及NUP光束参量有关. 相似文献
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屏蔽效应的研究对于防御电磁干扰,保证电子系统的正常工作是非常重要的。计算了屏蔽腔上开有不同形状的孔阵时对屏蔽效应的影响,分析比较了各种不同孔间距对屏蔽效应的影响。计算结果表明,圆形孔阵的穿透系数最小,方形孔阵次之,蜂巢形孔阵较大,但频谱分布基本一致。而对于哑铃形孔阵,由于孔面形状差异较大,孔面处磁流分布变化也较大,不仅穿透系数比前三者都大,而且高频时穿透系数的频率分布也发生较大改变。另外,随着孔阵中孔间距变大,孔之间的互耦减弱,耦合进屏蔽腔内的场强也变小。 相似文献
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Xiaoxu Lian 《Optics & Laser Technology》2011,43(7):1264-1269
Analytical expression for the propagation of nonparaxial cosh-Gaussian (ChG) beams diffracted by a rectangular aperture is derived based on the vector Rayleigh-Sommerfeld diffraction integrals and expansion of the aperture window function into a finite sum of complex Gaussian functions, and used to study the phase singularities of nonparaxial diffracted ChG vortex beams. The pair creation, annihilation, motion of phase singularities in the diffracted field and the dependence of position and number of phase singularities on the aperture and beam parameters, as well as on the beam nonparaxiality are illustrated by numerical examples. 相似文献
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Guoquan Zhou 《Optics Communications》2010,283(18):3383-3467
Based on the angular spectrum representation of an arbitrary electromagnetic beam and the method of stationary phase, an analytically vectorial structure of an apertured Laguerre-Gaussian beam in the far-field has been derived without any approximation. The analytical expressions of the energy flux of the TE term, the TM term, and the apertured Laguerre-Gaussian beam are also presented in the far-field, respectively. The energy flux distributions of the TE term, the TM term, and the apertured Laguerre-Gaussian beam are numerically demonstrated in the far-field reference plane. The influences of the f-parameter, the truncation parameter, the radial and angular mode numbers, and the dependent relation of angle on the energy flux distributions in the far-field of the TE term, the TM term, and the apertured Laguerre-Gaussian beam are also discussed in detail. 相似文献
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《Current Applied Physics》2018,18(7):793-798
Subwavelength aperture antenna arrays are designed and fabricated for potential applications in fluorescence sensing in the near UV/blue range. They are designed using finite-difference time-domain (FDTD) simulation, fabricated using focused ion beam etching and characterised using angular Fourier spectroscopy. The aperture arrays are formed in the top layer of an aluminum-silica-aluminum trilayer and produce a maximum simulated field intensity enhancement of 5.8 times at 406 nm and highly directive emission with a beamwidth of 8.3 deg. The normal incidence reflection response has been measured and shows reasonable agreement with modelled results. In addition, to investigate higher field intensity enhancements, bowtie aperture arrays are simulated and the influence of parameters such as dielectric gap, position of dipole source, and aperture shape and size are discussed and show enhancements up to 67 times are possible. 相似文献
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Zhangrong Mei 《Optics Communications》2011,284(22):5248-5252
The focal shifts of focused truncated random electromagnetic beams are investigated. Based on the complex Gaussian expansion method for a hard-edged aperture function, the analytical propagation formula of cross-spectral density matrix for a random electromagnetic beam focused by an optical system with a thin lens and a circular aperture is derived. The Fresnel numbers related with the beam and system parameters are defined and used to examine focal shifts. The dependence of the focal shifts on the different Fresnel numbers and polarization distribution are discussed in detail with numerical examples. 相似文献
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To obtain the image of an object obscured by moving scattering media, a set-up involving a lens with double aperture is employed. The condition for the minimum speed of the scattering media is first derived, the evaluation of which using the set-up parameters yields 0.038 km/h. An improved reconstructed image is then confirmed in the experiment. Advantages of the technique include the relief of the need, respectively, for a local reference beam and a mechanically very stable set-up. 相似文献
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Periodic slit screens are often installed in rectangular apertures either to mask the opening or to reduce transmitted noise. This investigation considers the higher-order scattered and transmitted sound from a point source through a periodic screen mounted in a rigid baffle. In particular, this paper considers the spatial characteristics, or directivity, of the scattered field for a particular higher order mode. Uncoupled higher-order mode analysis is used to estimate the scattered and transmitted sound fields for the selected mode of the aperture without the presence of the screen. Transmission coefficients for the screens are then calculated using the well established equivalent mass layer effect and applied to the calculated higher-order mode scattered and transmitted sound pressures. Using an anechoic chamber, measurements were made over a small arc of the scattered sound field through a range of screens of different aspect ratios but the same porosity. The screens consisted of equally spaced open slits and solid laths and the number of slits was reduced to change the aspect ratio. In each case the point source was positioned on the impinging side of the aperture so as to drive one particular scattered higher-order aperture mode at or near cut-on. Comparison of the measured and predicted sound pressures indicate that good estimates of the sound field can be obtained through the approach of applying simple corrections for the presence of the screens to the estimates for the open aperture established using uncoupled calculations for the higher-order modes. It is also shown that the results for a specific mode excited at one particular frequency are applicable at other excitation frequencies provided that the correct non-dimensionalisation is applied. 相似文献
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有孔双层屏蔽腔体的宽频带屏蔽效能 总被引:5,自引:3,他引:2
用扩展为可分析腔内高次模的传输线方法研究了有孔双层屏蔽腔体的屏蔽效能,该方法可以考虑腔内较宽的频带范围。计算了双层屏蔽腔内电场的屏蔽系数,与单层屏蔽腔内屏蔽系数的比较表明,采用双层屏蔽使得腔体的屏蔽效能大为提高。分析了双层屏蔽腔体孔缝耦合的共振效应、腔内的谐振。结果表明:满足共振效应成立条件时双层屏蔽腔内也发生共振现象,屏蔽效能在共振频率附近明显降低;在腔内的谐振点屏蔽系数出现极小值,此时屏蔽效果较差;在0.1~4.5 GHz的范围内,屏蔽系数随着频率的增加总体上呈下降趋势。 相似文献
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The propagation of elliptical Gaussian beam passing through paraxial optical systems with aperture is investigated analytically by using tensor method. The approximate formula for propagation of elliptical Gaussian beam through hard apertured optical systems is derived based on the fact that the circ function can be expanded into a finite sum of complex Gaussian functions. The derived formula provides a convenient tool for treating the propagation and transformation of elliptical Gaussian beam through apertured optical systems. As an application example, the propagation properties of elliptical Gaussian beam through apertured fractional Fourier systems are discussed. 相似文献