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1.
The approximative formula for the far-field diffraction of a Gaussian beam through a circular aperture is obtained by using the superposition of Gaussian beams instead of the aperture function, and the explicit expression for calculating the beam divergence is also gained. Using the formula, the influences of the aberrations on the far-field wavefront and the beam's divergence are researched, and the results show that the large aberrations badly affect the far-field wavefront and the divergence. It is suggested that the aberrations and the diffractions should be avoided when designing the transmitter. 相似文献
2.
The near- and far-field diffraction due to a circular aperture illuminated with partially coherent light produced by a turbulent
medium has been theoretically studied. Formulations are developed for investigating the near- and far-field diffraction patterns.
The phase structure function, which is generated by the turbulent medium and determines the partially coherent condition of
a light beam passing through it, is assumed to take both the Gaussian form and the 5/3-power law. Numerical results concerning
the far-field intensity distribution and the axial intensity distribution in the near-field region are presented in diagrams
and discussed. 相似文献
3.
Accurate, analytical series expressions for the far-field diffraction of a Gaussian beam normally incident on a circular and central obscured aperture are derived with the help of the integration of parts method. With this expression, the far-field intensity distribution pattern can be obtained and the divergence angle is deduced too. Using the first five items of the series, the accuracy can satisfy most laser application fields. Compared with the conventional numerical integral method, the series representation is very convenient for understanding the physical meanings. 相似文献
4.
The diffraction spectral intensity characteristics of a time-dependent Gaussian pulse from an apodized circular aperture in the far field are studied both theoretically and numerically. It is shown that the apodization of the diffracted Gaussian pulse spectrum can be found. Also the red or blue shift of the spectral intensity maximum of the incident pulse is presented. 相似文献
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6.
The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented. 相似文献
7.
The spectral characteristics of a pulsed hollow Gaussian beam passing through a circular aperture are studied. Based on the vectorial Rayleigh diffraction integrals, the analytical expressions of the spectra for the complex analytic signal representation and for the complex amplitude envelope representation are derived, respectively, and the comparison between them is made. The influences of the truncation parameter and the beam order on the spectral shifts and on the spectral switches are illustrated. It is shown that the spectrum for the complex analytic signal representation and that for the complex amplitude envelope representation are obvious different as the pulse shorter than an optical period. 相似文献
8.
Polarization singularities in near-field of Gaussian vortex beam diffracted by a circular aperture
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Polarization singularities in the near-field of Gaussian vortex beams diffracted by a circular aperture are studied by a rigorous electromagnetic theory.It is shown that there exist C-points and L-lines,which depend on off-axis displacement parameters along the x and y directions,waist width,wavelength,and topological charge of the diffracted Gaussian vortex beam,as well as on propagation distance.The results are illustrated by numerical calculations. 相似文献
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10.
Recurring to the characteristic of Bessel function, we give the analytic expression of the Fresnel diffraction by a circular aperture, thus the diffractions on the propagation axis and along the boundary of the geometrical shadow are discussed conveniently. Since it is difficult to embody intuitively the physical meaning from this series expression of the Fresnel diffraction, after weighing the diffractions on the axis and along the boundary of the geometrical shadow, we propose a simple approximate expression of the circular diffraction, which is equivalent to the rigorous solution in the further propagation distance. It is important for the measurement of the parameter of the beam, such as the quantitative analysis of the relationship of the wave error and the divergence of the beam. In this paper, the relationship of the fluctuation of the transverse diffraction profile and the position of the axial point is discussed too. 相似文献
11.
线偏振高斯光束经圆形光阑衍射后,其远场可表示成互相正交的横电(TE)项和横磁(TM)项之和。利用TE项和TM项的远场能流分布,导出了高斯衍射光束的TE项和TM项远场功率的解析表达式,由此可度量TE项和TM项在远场占总功率的比例。基于能流二阶矩的定义,给出了高斯衍射光束、TE项和TM项远场发散角的解析式以及三者远场发散角间的关系通式,重点分析了f参数和截取参数对远场发散角的影响。结果表明:随着f参数的增大,远场发散角先增大后趋向于各自的饱和值。截取参数对远场发散角的影响与f参数相关,当f参数较大时,截取参数对远场发散角的影响不明显;当f参数适中时,随着截取参数的增大,远场发散角先减小后趋向于各自的最小值;但当f参数较小时,高斯衍射光束和TM项二者的远场发散角出现一定的波动性。 相似文献
12.
线偏振高斯光束经圆形光阑衍射后,其远场可表示成互相正交的横电(TE)项和横磁(TM)项之和。利用TE项和TM项的远场能流分布,导出了高斯衍射光束的TE项和TM项远场功率的解析表达式,由此可度量TE项和TM项在远场占总功率的比例。基于能流二阶矩的定义,给出了高斯衍射光束、TE项和TM项远场发散角的解析式以及三者远场发散角间的关系通式,重点分析了f参数和截取参数对远场发散角的影响。结果表明:随着f参数的增大,远场发散角先增大后趋向于各自的饱和值。截取参数对远场发散角的影响与f参数相关,当f参数较大时,截取参数对远场发散角的影响不明显;当f参数适中时,随着截取参数的增大,远场发散角先减小后趋向于各自的最小值;但当f参数较小时,高斯衍射光束和TM项二者的远场发散角出现一定的波动性。 相似文献
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14.
《Physics letters. A》2006,360(2):394-399
Based on the generalized diffraction integral formula for treating the propagation of a laser beam through a misaligned paraxial ABCD optical system in the cylindrical coordinate system, analytical formula for a circular flattened Gaussian beam propagating through such optical system is derived. Furthermore, an approximate analytical formula is derived for a circular flattened Gaussian beam propagating through an apertured misaligned ABCD optical system by expanding the hard aperture function as a finite sum of complex Gaussian functions. Numerical examples are given. 相似文献
15.
基于麦克斯韦方程组解的矢量角谱表述与稳相法,在仅有远场近似的条件下,得到了被圆相位片衍射的空心高斯光束远场能流密度分布的解析表达式.结果表明,光束的总能流可以表示为自由项与附加项之和,其中附加项是相位片对能流分布的影响;总能流、自由项能流、附加项能流又可以分别表示为各自的TE项和TM项之和.利用所导出的公式,描绘了空心高斯光束的总能流、自由项能流、附加项能流及其各自的TE项与TM项能流的横截面分布图.讨论了截断参数与附加相移对纵向总能流分布的影响. 相似文献
16.
依据基尔霍夫衍射理论,利用幂级数展开的方法,推导出傍轴条件下高斯光束的矩孔及单缝衍射的近似计算公式,并通过数值计算、数值模拟等方法对衍射场的基本特性进行了讨论。 相似文献
17.
Zhou G. Q. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(1):149-155
In the far-field, the TM polarized Gaussian beam is just a sum of two orthogonal terms:
the TE and the TM terms. The analytical expressions for the ratios of the powers of the TE
and the TM terms to that of the TM polarized Gaussian beam are obtained without any
approximation. The contributions of the powers of the TE and TM terms to the power of the
TM polarized Gaussian beam only depend on the f-parameter. The analytical
divergence angles of the TE term, the TM term, and the TM polarized Gaussian beam are
derived. The formulae of the kurtosis parameters of the TE term, the TM term, and the TM
polarized Gaussian beam are also presented. The divergence angles and the kurtosis
parameters are only determined by the f-parameter. Relations among the
divergence angles and the kurtosis parameters of the TE term, the TM term, and the TM
polarized Gaussian beam are presented, respectively. The influence of the
f-parameter on the ratios of the powers of the TE and the TM terms to
the power of the TM polarized Gaussian beam, the far-field divergence angles, and the
kurtosis parameters are numerically analyzed. 相似文献
18.
Based on the vectorial Rayleigh diffraction integral and the hard-edge aperture function expanded as the sum of finite-term complex Gaussian functions, an approximate analytical expression for the propagation equation of vectorial Gaussian beams diffracted at a circular aperture is derived and some special cases are discussed. By using the approximate analytical formula and diffraction integral formula, some numerical simulation comparisons are done, and some special cases are discussed. We find that a circular aperture can produce the focusing effect but the beam becomes the shape of ellipse in the Fresnel region. When the Fresnel number is equal to unity, the beam is circular and the focused spot reaches a minimum. 相似文献
19.
Analytical nonparaxial vectorial electric field expressions for both Gaussian beams and plane waves diffracted through a circular aperture are derived by using the vector plane angular spectrum method for the first time,which is suitable for the subwavelength aperture and the near-field region.The transverse properties of intensity distributions and their evolutions with the propagating distance,and the power transmission functions for diffracted fields containing the whole field,the evanescent field and the propagating field are investigated in detail,which is helpful for understanding the relationship between evanescent and propagating components in the near-field region and can be applied to apertured near-field scanning optical microscopy. 相似文献