共查询到20条相似文献,搜索用时 15 毫秒
1.
Generalized Stokes parameters of stochastic spatially and spectrally partially coherent electromagnetic pulsed beams 总被引:1,自引:0,他引:1
The analytical expressions for the generalized (two-point) Stokes parameters of stochastic electromagnetic Gaussian Schell-model pulsed (GSMP) beams propagating in free space are obtained. The changes in the spectral Stokes parameters in free space propagation are studied. The dependence of on-axis and transverse spectral Stokes parameters of stochastic electromagnetic GSMP beams on the pulse parameters including pulse duration and temporal coherence length is stressed and illustrated numerically. The results are interpreted physically. 相似文献
2.
Haixia Wang Chaoliang Ding Zhiguo Zhao Yongtao Zhang Liuzhan Pan 《Optics & Laser Technology》2012,44(6):1800-1807
Based on the generalized Rayleigh–Sommerfeld diffraction integral, the analytical expression for 3×3 cross-spectral density matrix of nonparaxial spatially and spectrally partially coherent electromagnetic Cosh-Gaussian (ChG) pulsed beams propagating in free space is derived, and used to formulate the spectral density and spectral degree of polarization of electromagnetic pulsed beams at the z-plane. It is found that the parameters f and fαα are the key parameters in determining the nonparaxiality of spatially and spectrally partially coherent electromagnetic ChG pulsed beams. And the decentered parameter, pulse duration and temporal coherence length can change the nonparaxial behavior of the electromagnetic ChG pulsed beams. The effect of decentered parameter, pulse duration and temporal coherence length on the spectral density and spectral degree of polarization of electromagnetic ChG pulsed beams is illustrated through numerical calculations. Propagation of nonparaxial spatially and spectrally partially coherent electromagnetic Gaussian Schell-model pulsed beams can be treated as a special case when the decentered parameter of electromagnetic ChG pulsed beams approaches to zero. 相似文献
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Dongbing Liu 《Optics Communications》2010,283(3):379-385
The analytical expression for the spectrum of spatially and spectrally partially coherent cosh-Gaussian pulsed (ChGP) beams focused by an aperture lens is derived and used to study their spectral properties at the focal plane and on the axis. The effect of the truncation parameter, spatial correlation parameter, decentered parameter and temporal coherence length on the spectral shifts and spectral switches of spatially and spectrally partially coherent ChGP beams is stressed. The results are illustrated numerically and interpreted physically. 相似文献
7.
The analytical propagation expression of partially coherent flat-topped vortex beams through a paraxial optical ABCD system is derived, and it then is used to investigate the coherence vortex properties of partially coherent flat-topped vortex
beams in the Fourier transform and fractional Fourier transform systems. It is shown that in the Fourier transform system
the coherence vortex depends on the flat-topped beam order N, spatial coherence parameter α and position (x
1,y
1) of the reference point, whereas in the fractional Fourier transform system the flat-topped beam order N does not affect the spectral degree of coherence. Furthermore, in both transform systems, depending on the choice of the
reference point, the zero value point of the spectral degree of coherence may be present or absent. In particular, if x
1=y
1=0 is selected, the phase at the zero value point of the spectral degree of coherence may be determinate; thus the coherence
vortex does not exist. 相似文献
8.
The effects of turbulent atmosphere on the spectral degree of polarization (SDP) of aberrated partially coherent flat-topped beam were studied. Analytical formula for the SDP was derived. Detailed analyses of the SDP demonstrate that it is strongly affected by astigmatic aberration when propagating through turbulent atmosphere. The effect of source parameters such as correlation length and order of flatness as well as the strength of the atmospheric turbulence effect () on the SDP were analysed. The analyses are illustrated by numerical examples. 相似文献
9.
对部分空间和部分光谱相干2维高斯-谢尔模型脉冲光束在自由空间传输的光谱和时间特性做了详细的数值研究。结果表明,部分空间和部分光谱相干高斯-谢尔模型脉冲光束在自由空间传输中发生了光谱移动,光谱移动与场点位置、空间相关长度和时间相干长度有关。在轴上,光谱出现蓝移,相对光谱移动随传输距离的增加而增大,随空间相关长度和时间相干长度的增加而减小,并逐渐趋于一定值。在轴外,光谱出现蓝移和红移,并与空间相关长度和时间相干长度有关。脉冲时间波形不变,对所得主要结果做了物理解释。 相似文献
10.
Paraxial propagation of partially coherent flat-topped beam 总被引:3,自引:0,他引:3
The propagation of flat-topped beam passing through a paraxial optical ABCD system is extended to partially coherent case and has been studied in detail. Based on Wigner distribution function (WDF), the irradiance distribution of partially coherent flat-topped beam is derived. Furthermore, two propagation parameters, such as M2-factor and Power in Bucket (PIB) are illustrated analytically and numerically. 相似文献
11.
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. 相似文献
12.
C. L. Ding L. Z. Pan B. Lü 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(2):329-336
Taking the stochastic electromagnetic J
0-correlated Schell-model pulsed
(JSMP) beam as a typical example of stochastic spatially and spectrally
partially coherent electromagnetic pulsed beams, the analytical expressions
for the cross-spectral density matrix, spectral density, spectral degree of
polarization and spectral degree of coherence of stochastic electromagnetic
JSMP beams propagating in free space are derived, and used to study the
changes in the spectrum, polarization, and coherence of stochastic spatially
and spectrally partially coherent electromagnetic JSMP beams. It is shown
that the on-axis spectrum is blue-shifted in free-space propagation and is
dependent on the pulse temporal coherence length and spatial correlation
parameter. The distribution of the on-axis spectral degree of polarization
depends on the frequency and spatial correlation parameter. The spectral
degree of coherence increases with increasing pulse temporal coherence
length. The results derived are interpreted physically. 相似文献
13.
Experimental generation of a partially coherent flat-topped beam 总被引:1,自引:0,他引:1
An efficient optical system is proposed to generate a partially coherent flat-topped (FT) beam theoretically. Furthermore, we report the experimental generation of a partially coherent FT beam based on the proposed optical system. The intensity distribution and the modulus of the square of the spectral degree of coherence of the generated partially coherent FT beam are measured. The experimental results are consistent with the theoretical results. 相似文献
14.
《Waves in Random and Complex Media》2013,23(4):513-523
Abstract In this paper, we study the effects of turbulent atmosphere on the degree of polarization of a partially coherent electromagnetic beam, which propagates through it. The beam is described by a 2?2 cross–spectral density matrix and is assumed to be generated by a planar, secondary, electromagnetic Gaussian Schell–model source. The analysis is based on a recently formulated unified theory of coherence and polarization and on the extended Huygens–Fresnel principle. We study the behaviour of the degree of polarization in the intermediate zone, i.e. in the region of space where coherence properties of the beam and the atmospheric turbulence are competing. We illustrate the analysis by numerical examples. 相似文献
15.
Polarization changes in partially coherent electromagnetic beams propagating through turbulent atmosphere 总被引:4,自引:0,他引:4
Mohamed Salem Olga Korotkova Aristide Dogariu Emil Wolf 《Waves in Random and Complex Media》2004,14(4):513-523
In this paper, we study the effects of turbulent atmosphere on the degree of polarization of a partially coherent electromagnetic beam, which propagates through it. The beam is described by a 2⊗2 cross-spectral density matrix and is assumed to be generated by a planar, secondary, electromagnetic Gaussian Schell-model source. The analysis is based on a recently formulated unified theory of coherence and polarization and on the extended Huygens-Fresnel principle. We study the behaviour of the degree of polarization in the intermediate zone, i.e. in the region of space where coherence properties of the beam and the atmospheric turbulence are competing. We illustrate the analysis by numerical examples. 相似文献
16.
The propagation of partially coherent flat-topped (PCFT) beams with non-circular symmetries in a turbulent atmosphere is investigated and an analytical formula for the average intensity is derived. Detailed analyses of PCFT beams in a turbulent media led to the derivation of analytical formulae. These formulae demonstrated that higher-order PCFT beams are less broadened in comparison with those with smaller orders and also demonstrated that PCFT beams with smaller correlation lengths are more broadened than the others. The Strehl ratio for PCFT beams is also calculated and the results show that PCFT beams with a higher order of flatness and smaller correlation length are less affected in turbulent media. 相似文献
17.
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. 相似文献
18.
采用相屏近似处理方法对激光通过湍流大气的传输进行了数值模拟。从数值模拟的结果拟合出两个公式:一是通过湍流前后部分相干平顶高斯光束的束宽平方比随阶数、传输距离和湍流强度的变化关系式;一是通过湍流后的相干长度随初始光束相干长度、湍流相干长度的变化关系式。研究发现:部分相干平顶高斯光束分解为相互独立的厄米-高斯光束的叠加;相干性越差的光束受到湍流的影响程度就越小;湍流对光束传输的影响与光束自身相干特性对其传输的影响之间是不相关的。 相似文献
19.
The concept of existing scalar coherent four-petal Gaussian (FPG) beam is extended to the more general partially coherent electromagnetic four-petal Gaussian (PCFPG) beam, and the cross-spectral density matrix of the latter is derived in analytical expressions. Intensity distributions and degree of polarization in free space are investigated by numerical examples. Results show that propagation properties of the PCFPG beam are different from their scalar coherent and scalar partially coherent counterparts. Both intensity distributions and polarization strongly depend on transversal coherence lengths. When the propagation distance increases to a large value, intensity distributions of PCFPG beams convert into the Gauss profile. Polarization of PCFPG beams shows an oscillating characteristic upon propagation, and the oscillation would enhance with the increase of coherence lengths. These results may find potential applications in beam shaping and free space optical communications. 相似文献
20.
采用相屏近似处理方法对激光通过湍流大气的传输进行了数值模拟。从数值模拟的结果拟合出两个公式:一是通过湍流前后部分相干平顶高斯光束的束宽平方比随阶数、传输距离和湍流强度的变化关系式;一是通过湍流后的相干长度随初始光束相干长度、湍流相干长度的变化关系式。研究发现:部分相干平顶高斯光束分解为相互独立的厄米-高斯光束的叠加;相干性越差的光束受到湍流的影响程度就越小;湍流对光束传输的影响与光束自身相干特性对其传输的影响之间是不相关的。 相似文献