共查询到20条相似文献,搜索用时 15 毫秒
1.
The rotational frequency shift is studied for fields of arbitrary states of coherence and polarization. It is shown that the power spectrum of the field in the rotating frame is influenced both by the degree of polarization and the degree of coherence. Examples for some model field classes are given. 相似文献
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We study the spatial coherence properties of a three-dimensional, primary, quasi-homogeneous, and isotropic source and the far field that it generates. We assess the spectrum, degree of polarization, electromagnetic degree of coherence, and effective degree of coherence of the source and of the far field. We also demonstrate the formalism for a spherical Gaussian Schell-model current source. The polarization properties of light are fully accounted for in the analysis, and it is found that certain results pertaining to scalar coherence theory are reproduced also within the electromagnetic treatment. 相似文献
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Jingjing Chen Feinan Chen Yanru Chen Yu Xin Yongqing Wang Qi Zhao Muchun Zhou 《Optics Communications》2012,285(19):3955-3960
The coherence properties of the scattered field generated by linearly polarized and uniformly unpolarized electromagnetic plane waves incident on anisotropic quasi-homogeneous media are studied. The analytical expressions for the spectral density and the spectral degree of coherence of the three dimensional scattered field are derived. The results of the numerical simulations indicate that not only the properties of the anisotropic media have a great effect on the coherence properties of the scattered field, but also the polarization of the incident wave. And most important, the effect of the polarization of the incident wave on the coherence properties of the scattered field nearly concerns the properties of the anisotropic media. There are also close and interesting relations between the coherence properties of the scattered field that generated by the anisotropic media and by the corresponding isotropic media. 相似文献
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半导体光放大光纤环形激光器的偏振混沌与相干性 总被引:3,自引:0,他引:3
研究了基于半导体光放大器(SOA)的光纤环形激光器的偏振混沌光的特性及其相干性。实验采集激光器的输出功率和偏振度,得到了基于半导体光放大器的光纤环形激光器的输出从自发辐射到受激辐射、再到偏振态混沌激光辐射的演化过程。利用马赫-曾德尔(M-Z)干涉仪验证了混沌激光的相干性,并发现混沌干涉只有零级。测量不同光程差时干涉仪的输出功率,计算相应的干涉条纹可见度,进一步算得混沌激光的相干时间约为40 ps。这一结果与根据光谱计算的该混沌激光的相干时间43 ps基本一致。实验还测得该混沌激光的相干性与半导体光放大器的电流无关。并指出了混沌激光相干应用于低相干光源探测领域的灵敏度和分辨力优势。 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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It is demonstrated for stationary fields that when the polarization state of the electric field can be modified arbitrarily the maximal value of the modulus of the degree of coherence proposed by Wolf [Phys. Lett. A312, 263 (2003)] is equal to the largest intrinsic degree of coherence. In addition, when the light is a mixing of a coherent light that satisfies the factorization condition in the two spatial variables with a statistically uncorrelated, partially coherent, perfectly polarized light, but with a nonparallel polarization state, we show that the polarization modifications that maximize the modulus of the Wolf degree of coherence lead to a light that also satisfies the factorization condition. 相似文献
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Tomohiro Shirai 《Optics Communications》2010,283(22):4478-4483
A physical interpretation of the recipe for synthesizing genuine 2 × 2 cross-spectral density matrices that characterize stochastic electromagnetic sources and beams is described. In this interpretation, the synthesized field is regarded as an incoherent superposition of spatially coherent fields originating from a partially polarized, spatially incoherent virtual source. The coherence and the polarization properties of the synthesized field are also examined in view of this interpretation. As a result, we found that the spectral degree of coherence and that of polarization of the synthesized field are generally different from those of the virtual source by the effect of the superposition. We also found, however, that there are some situations in which the spectral degree of polarization of the synthesized field remains unchanged even though the superposition takes place. 相似文献
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Román Castañeda 《Optics Communications》2011,284(18):4114-4123
Random stationary electromagnetic fields can be modeled in terms of point sources disposed onto two distinct layers, named the radiant and the virtual layers. It allows describing the propagation of the power and the states of spatial coherence and polarization of the field by means of separate phase-space ray-maps. Spatial coherence of the field, correlation of the polarization angles and achievement of the Fresnel-Arago laws within the structured spatial coherence supports are the necessary conditions that determine the electromagnetic point sources in the virtual layer. The contributions of these sources produce two types of modulations on the electromagnetic field at the observation plane, one of them of scalar type is the interferometric power modulation, and the other one of vector type is de modulation of the polarization state provided by the radiant point sources, according to the Stokes' parameters. Some examples are presented. 相似文献
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用量子Maxwell-BlochC-数方程讨论了存在均匀消相阻尼的一维稀薄等离子体系统中电场和极化的发展过程及相干特性,给出了线性阶段的解析结果和非线性阶段的数值结果。数值结果显示了电场和极化的发展过程及随机源对它们的影响。最后给出了电场和极化的相干度及自由电子对相干度的影响。当等离子体频率远小于辐射频率时,自由电子的作用可以忽略。 相似文献
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Nicole M. Trease Krishna K. Dey Philip J. Grandinetti 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(2):334-339
Central transition (CT) sensitivity enhancement schemes that transfer polarization from satellites to the CT through selective saturation or inversion of neighboring satellite transitions have provided a welcome improvement for magic-angle spinning spectra of half-integer quadrupole nuclei. While many researchers have investigated and developed different methods of creating enhanced CT populations, here we investigate the conversion of these enhanced CT populations into observable CT coherence. We show a somewhat unexpected result that a conversion pulse length optimized for maximum sensitivity on equilibrium populations may not be optimum for an enhanced (non-equilibrium) polarization. Furthermore, CT enhancements can be lost if excessive rf field strength is used to convert this enhanced polarization into CT coherence. While a maximally enhanced CT signal is expected when using a perfectly selective CT conversion pulse, we have found that significant sensitivity loss can occur when using surprisingly low rf field strengths, even for sites with relatively large quadrupole coupling constants. We have systematically investigated these issues, and present some general guidelines and expectations when optimizing the conversion of enhanced (non-equilibrium) CT populations into observable CT coherence. 相似文献
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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. 相似文献
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Based on the extended Huygens–Fresnel diffraction integral and the unified theory of coherence and polarization, the slanting propagation properties of stochastic electromagnetic twist anisotropic Gaussian–Schell model (ETAGSM) beams in turbulent atmosphere have been investigated. Both numerical calculation and physical interpretation are obtained. The influence of the atmospheric turbulence and the source parameters on the polarization distribution, intensity distribution and coherence distribution has been studied in great detail. The investigation reveals that slanting propagation can weaken the influence of atmospheric turbulence on the spectral properties of stochastic ETAGSM beams more obviously. It is also shown that we can modulate the spectral degree of polarization in the output plane especially in the far field by simply controlling the coherence, the spot width or the twisty properties of the source beams. The distribution of the spectral degree of polarization and cross-polarization of the beams in the output plane is also given out. 相似文献
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When a totally unpolarized light is scattered by a medium that spatially totally depolarizes incident polarized light, the scattered field presents an increase of the order described by the temporal degree of polarization. We analyze the behavior of some polarization and coherence properties in such a physical situation. 相似文献
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On the basis of a plane-wave spectrum representation, the polarization features of a transverse quasimonochromatic non-paraxial field have been studied. A relationship has been established between the polarization characteristics in the near field and the coherence and symmetry properties of the beam in the far field. 相似文献
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Nonclassical polarization properties of a quantum field propagating through non-Kolmogorov turbulence are studied in a turbulent atmosphere paraxial channel. The analytic equation for the quantum degree of polarization of linearly polarized light is obtained. It is shown by numerical simulation that the polarization fluctuations of the quantum field are a function of the turbulent strength, the photon number, the propagation distance, the fractal constant α and the coherence length ρ0. 相似文献
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It is shown how surface plasmons that travel between the slits in Young's interference experiment can change the state of spatial coherence of the field that is radiated by the two apertures. Surprisingly, the coherence can both be increased and decreased, depending on the slit separation distance. This results in a modulation of the visibility of the interference fringes. Since many properties of a light field-such as its spectrum, polarization, and directionality - may change on propagation and are dependent on the spatial coherence of the source, our results suggest that the use of surface plasmons provides a new way to alter or even tailor the statistical properties of a light field. 相似文献