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1.
Analytic expressions and computed examples are given to elucidate the coherence and polarization properties of Stokes beams, i.e. beams formed by superposition of a completely unpolarized and a completely polarized electromagnetic Gaussian Schell-model beam. We found that superposition of such two beams cannot form a Stokes beam with a constant state of polarization on propagation. An additional constraint on the source plane parameters of the two Gaussian Schell-model beams is proposed. The resultant Stokes beam with a constant state of polarization on propagation is found to be a Gaussian Schell-model beam with the same variances as the two constituent Gaussian Schell-model beams. However, the modulus of the Gaussian intensity distributions across the source planes of these beams may be different. 相似文献
2.
The spatial correlation properties and the spectral intensity distributions of focused Gaussian Schell-model (GSM) array beams are studied in detail. The closed-form expressions for the spectral degree of coherence and the spectral intensity of focused GSM array beams are derived. It is shown that the spectral degree of coherence of focused GSM array beams is the same as that of focused GSM beams in the focal plane. On the other hand, it is found that, in the focal plane the spectral intensity distribution of focused GSM array beams is the fringe pattern when the value of the coherence length is small. However, it becomes one peak located at the center as the value of the coherence length is large enough. In the focal plane, the spectral intensity maximum increases and the width of the normalized spectral intensity distribution decreases as the beam number increases. In general, for GSM array beams, the width of the modulus of the spectral degree of coherence in the focal plane always exceeds that of the normalized spectral intensity distribution, which is different from the behavior of focused GSM beams. In addition, the power in the bucket (PIB) and the beam propagation factor (M2 factor) are also discussed. The main results are explained physically. 相似文献
3.
Based on the propagation law of cross-spectral density function,
studied in this paper are the coherence vortices of partially
coherent, quasi-monochromatic singular beams with Gaussian
envelope and Schell-model correlator in the far field, where our
main attention is paid to the evolution of far-field coherence
vortices into intensity vortices of fully coherent beams. The
results show that, although there are usually no zeros of
intensity in partially coherent beams with Gaussian envelope and
Schell-model correlator, zeros of spectral degree of coherence
exist. The coherence vortices of spectral degree of coherence
depend on the relative coherence length, mode index and
positions of pairs of points. If a point and mode index are kept
fixed, the position of coherence vortices changes with the
increase of the relative coherence length. For the low coherent
case there is a circular phase dislocation. In the coherent
limit coherence vortices become intensity vortices of fully
coherent Laguerre--Gaussian beams. 相似文献
4.
The analytical expression for the beam propagation factor (M2-factor) of Gaussian Schell-model (GSM) array beams propagating through atmospheric turbulence is derived. It is shown that the M2-factor of GSM array beams depends on the beam number, the relative beam separation distance, the beam coherence parameter, the type of beam superposition, and the strength of turbulence. The turbulence results in an increase of the M2-factor. However, for the superposition of the intensity the M2-factor is less sensitive to turbulence than that for the superposition of the cross-spectral density function. The M2-factor of GSM array beams is larger than that of the corresponding Gaussian array beams. However, the M2-factor of GSM array beams is less affected by turbulence than that of the corresponding Gaussian array beams. For the superposition of the cross-spectral density function a minimum of the M2-factor of GSM array beams may appear in turbulence, which is even smaller than that of the corresponding single GSM beams. 相似文献
5.
衍射扭曲高斯-谢尔模型光束在远场的光谱移动和光谱开关 总被引:1,自引:0,他引:1
从部分相干光的传输理论出发,研究了被光阑衍射扭曲高斯-谢尔模型光束远场的光谱变化规律。结果表明,扭曲高斯-谢尔模型光束在远场也会出现光谱移动和光谱开关效应。与衍射高斯-谢尔模型光束情况相比,光谱移动和光谱开关效应不仅与光束空间相关性、截断参量和源光谱谱宽有关,光束的扭曲因子也会对衍射扭曲高斯-谢尔模型光束远场的光谱移动和光谱开关效应产生影响。通过数值计算结果详细讨论了光束扭曲因子影响衍射扭曲高斯-谢尔模型远场光谱的规律。 相似文献
6.
7.
Chunyi Chen Huamin Yang Shoufeng Tong Yan Lou 《Applied physics. B, Lasers and optics》2013,111(3):373-381
The spatiotemporal coherence properties of broadband Gaussian Schell-model (GSM) beams with different spectral bandwidths propagating through atmospheric turbulence are numerically calculated and analyzed. The results show that although the spatial coherence properties of an intermediate-broadband GSM beam almost do not depend on the spectral bandwidth, those of its ultra-broadband counterpart do. The temporal coherence of an ultra-broadband GSM beam not only has radial dependence in the observation plane, but also varies with the increasing propagation distance; however, the same behavior does not hold for an intermediate-broadband GSM beam of which the temporal coherence remains nearly invariable as the radial distance of the observation point or propagation distance changes. 相似文献
8.
基于相干性和偏振性统一理论,采用Rytov相位结构函数平方近似推导出了部分相干电磁平顶光束在湍流大气中传输的偏振度、相干度和光谱强度公式,并研究了湍流对其传输特性的影响.研究表明,偏振度和相干度与源光谱的带宽无关.大气湍流使得不同阶数的部分相干电磁平顶光束的偏振度经长程传输后均趋于其初始值.大气湍流使得部分相干电磁平顶光束与电磁高斯-谢尔模型光束相干度的差别减小,并导致相干度的振荡和相位奇异现象消失.大气湍流使得相干性较好的部分相干电磁平顶光束的光谱跃变现象消失. 相似文献
9.
In view of second-order coherence theory, the generalized diffractive axicon illuminated by partially coherent Gaussian Schell-model (GSM) beams is analyzed. An analytical equation for focal depth of axicon without aperture illuminated by spatial partially coherent GSM beam is derived. We showed that the off-axis images can be evaluated by using the method of stationary phase at any correlation state, hence we demonstrated that the intensity distribution of diffracted beam is a superposition of Bessel Beams of various orders. We also showed that the diffracted beam is nondiffractive only on the boundaries of the focal depth. 相似文献
10.
The anomalous spectral behaviors of partially coherent polychromatic hollow Gaussian Schell-model beams (HGSMBs) diffracted by a slit are investigated. Besides spectral switches, asymmetrical dual-peak spectral split and multi-peak spectral split are observed. In the vicinity of the positions where spectral switches occur, flat-topped spectrum can be obtained, the bandwidth of which is adjustable by changing the transverse coherence width and the observation position. The flat-topped spectrum has potential application for creating probe beams in optical metrology systems and generating broadband optical sources in fiber optic sensor interface systems. 相似文献
11.
大气湍流对部分相干电磁平顶光束传输的影响 总被引:1,自引:1,他引:0
基于相干性和偏振性统一理论,采用Rytov相位结构函数平方近似推导出了部分相干电磁平顶光束在湍流大气中传输的偏振度、相干度和光谱强度公式,并研究了湍流对其传输特性的影响.研究表明,偏振度和相干度与源光谱的带宽无关.大气湍流使得不同阶数的部分相干电磁平顶光束的偏振度经长程传输后均趋于其初始值.大气湍流使得部分相干电磁平顶光束与电磁高斯一谢尔模型光束相干度的差别减小,并导致相干度的振荡和相位奇异现象消失.大气湍流使得相干性较好的部分相干电磁平顸光束的光谱跃变现象消失. 相似文献
12.
基于广义惠更斯-菲涅耳原理,采用Rytov相位结构函数二次近似和硬边窗口函数的复高斯展开法,推导了受光阑限制的多色高斯-谢尔模型(GSM)光束在大气湍流中的二阶矩束宽公式。研究表明:二阶矩束宽随着大气湍流折射率结构常数、源光谱带宽和光束传输距离的增加而增大,随着光束截断参数和光束相干参数的增加而减小;并且,当源光谱带宽越大、光束截断参数和光束相干参数越小,则湍流对受光阑限制的多色GSM光束扩展的影响就越小。关键词: 相似文献
13.
Can two partially coherent cosh-Gaussian beams generate far fields with the same spectral degree of coherence?
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Taking partially coherent cosh--Gaussian (ChG) beams as an example
of more general partially coherent beams, we have studied the
spectral degree of coherence of partially coherent ChG beams in the
far field. It is shown that, unlike Gaussian Schell-model (GSM)
beams, in the strict sense there do not exist two partially coherent
ChG beams which can generate far fields with the same spectral
degree of coherence. However, under certain conditions it is
possible to find two partially coherent ChG beams with the same
spectral degree of coherence in the far field. 相似文献
14.
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
15.
According to the paraxial form of the extended Huygens-Fresnel principle, the analytical formulas of the on-axis average irradiance and the on-axis scintillation index for a rectangular array Gaussian Schell-model (RAGSM) beams in atmospheric turbulence have been derived. The on-axis bit error rate has been analyzed quantitatively. Their effects of the turbulence intensity, the initial correlation length, and the array parameters including the beamlet number (M and N) and the array separation distance (x0 and y0) have been discussed. The results show that the correlated and uncorrelated superposition RAGSM beams exhibit the different on-axis intensity distribution, the similar variation of the on-axis scintillation and the bit error rate. At the nearer propagation distance the on-axis scintillation rises against propagation distance with the increasing beamlet number and the decreasing array separation distance, whereas the situation is reversed at the farther propagation distance. The effects of array parameters on the bit error rate are similar to that on the scintillation. For a given propagation distance the scintillation index increases with the stronger coherence and the larger waist width of the array beam. 相似文献
16.
The effect of turbulence on the spreading of radial Gaussian Schell-model (GSM) array beams is studied quantitatively by examining the mean-squared beam width. The analytical expression for the turbulence distance z T of radial GSM array beams is derived by using the integral transform technique, which indicates within what ranges radial GSM array beams will be less affected by turbulence. It is shown that the effect of turbulence on the spreading of radial GSM array beams can be reduced by choosing the suitable array beam parameters and the type of the beam superposition. In addition, a comparison with the previous work is also made. 相似文献
17.
Suye Lü 《Optics Communications》2007,279(1):150-158
Based on the theory of optical coherence, the spatial coherence properties and directionality of partially coherent cosh-Gaussian (ChG) beams are studied. It is shown that unlike Gaussian Schell-model (GSM) beams, in the strict sense there do not exist partially coherent ChG beams which may produce the same far-field radiant intensity distribution as a fully coherent laser beam. However, under certain conditions it is possible to find partially coherent ChG beams with the same far-field radiant intensity distribution as a fully coherent laser beam. 相似文献
18.
Turbulence-induced changes in degree of polarization, degree of coherence and spectrum of partially coherent electromagnetic beams
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Based on a recently formulated unified theory of coherence
and polarization, a method is described to study turbulence-induced
changes in the polarization, the coherence and the spectrum of
partially coherent electromagnetic beams on propagation. The
electromagnetic Gaussian Schell-model beam is taken as a typical
example of partially coherent electromagnetic beams, and the
closed-form expressions for the degree of polarization, the degree
of coherence and the spectrum of electromagnetic Gaussian
Schell-model beams propagating through atmospheric turbulence are
derived in the quadratic approximation of Rytov's phase structure
function. Some interesting results are obtained, which are
illustrated by numerical examples and are explained in physics. 相似文献
19.
Z. Tong O. Korotkova Y. Cai H. T. Eyyuboglu Y. Baykal 《Applied physics. B, Lasers and optics》2009,97(4):849-857
With the help of the generalized Huygens–Fresnel principle and the tensor approach for electromagnetic stochastic beams we
investigate the behavior of their two-point spatial correlation properties on interaction with a laser resonator. In particular,
the evolution of the degree of coherence, of the degree of cross-polarization and of the intensity correlations (at one and
two points in space) is analyzed for typical beams and cavities. The theory is illustrated by numerical curves pertaining
to various correlation properties of typical electromagnetic Gaussian Schell-model beams. 相似文献