Superimposed volume holograms for measuring the phase and degree of mutual coherence of a light wave

Superimposed volume holograms, which make it possible to determine the phase and degree of mutual coherence of a stationary light wave consisting of partially coherent plane components incident on the holograms at different angles are proposed. To find these parameters of the light wave, the intensities of the waves reconstructed by the holograms are measured in the case of amplitude and phase modulation of the wave incident on the holograms. The phases and degrees of mutual coherence of the components of the wave incident on the holograms are found from the measured data. The holograms are studied based on the modal theory of superimposed volume holograms.     

Optical fibre excitation by partially coherent sources

Sources for optical fibre excitation have previously been assumed to be either totally coherent or incoherent. This paper formulates the modal excitation problem for partially coherent sources. The modal excitation coefficients are given in terms of the source complex degree of coherence and numerical results and simple analytical expressions appropriate to multimode step index fibres are presented. The assumption of equal modal power when excitation is by a very incoherent source is examined and the following simple criterion developed: for highly incoherent sources, modes with eigenvaluesU < the reciprocal of the coherence length, measured in units of fibre radius, are approximately equally excited, while the remaining modes carry little power.     

Geometric optics approach to optical fibre excitation by partially coherent sources

A general partially coherent source field on the end of an optical fibre has been represented by a characteristic angular spectrum of independent plane waves. The launching of both trapped and tunnelling (leaky) power is investigated for both step and graded-index fibres by considering the effect of one component of the angular spectrum, using geometric optics acceptance theory. The effect of the degree of coherence on the pulse response of the fibres is briefly discussed.     

部分相干光对周期性局域空心光束的影响

用旋转毛玻璃和光阑把激光变成部分相干光, 再经过双轴棱锥系统把一束平行光变成两束同频率但不同径向波矢分量的无衍射贝塞尔光, 相干叠加产生了部分相干的周期性局域空心光束. 通过干涉理论与实验结果相互佐证, 得出局域空心光束的周期为2.5 mm. 进一步探究入射光场相干度对产生局域空心光束的影响, 发现随着相干度的降低局域空心光束中心暗斑与周围光强的衬比度会降低, 但不影响局域空心光束的周期以及中心暗斑尺寸.     

Phase singularities and coherence vortices in linear optical systems

It is demonstrated for a time-invariant linear optical system that there exists a definite connection between the optical vortices (phase singularities of the field amplitude) which appear when it is illuminated by spatially coherent light and the coherence vortices (phase singularities of the field correlation function) which appear when it is illuminated by partially coherent light. Optical vortices are shown to evolve into coherence vortices when the state of coherence of the field is decreased. Examples of the connection are given. Furthermore, the generic behavior of coherence vortices in linear optical systems is described.     

部分相干椭球光笼

 从理论上研究部分相干光束经透镜聚焦的三维光强分布。研究结果表明，在几何焦点附近的光强分布不仅依赖于入射部分相干光束的光强分布，而且还依赖于入射光束的空间相干度。基于这一点，提出了一种控制部分相干光束的空间相干度，在几何焦点附近获得了类似椭球光笼形状的光强分布的新方法。通过控制入射部分相干光的空间相干度，来改变聚焦在几何焦点附近的三维光强分布，从而获得希望得到的光强分布。     

相干模表示的部分相干高斯-谢尔光束的相位-空间积

与传统的相干激光光束的评价不同,对部分相干光束质量进行评价时,不仅要反映其远场发散特性,而且还要能体现光源本身的部分相干性。根据部分相干光的相干模表示法,推导了由部分相干光源所产生光束的相位一空间积Q。与前人在相干光源情形下得到的结论相比,得出的相位一空简积Q不仅包含各个全相干模基元线性组合的贡献,而且还有来自不同的全相干模基元之间相互作用的贡献。     

Propagation of partially coherent Gaussian laser beams in graded-index fibres

Using statistical approach the author has solved the equations for the mutual coherence function of partially coherent Gaussian laser beams in graded-index fibres. The expressions for the complex degree of coherence and the intensity distribution have also been shown that the self-focusing length inside the fibre depends upon the degree of coherence. The result have been discussed for both conical and cylindrical guides.     

Propagation of a partially coherent beam through Selfoc fibers

Propagation of a partially coherent beam through a Selfoc fiber is considered. The inhomogeneous Helmholtz equations satisfied by the mutual coherence function are solved using the modal expansion. The result is applied to the cases when the incident beam is either incoherent or coherent. An expression for the intensity distribution is also obtained.     

Focusing properties of twisted Gaussian Schell-model beams passing through a system: The aperture lens or the aperture and lens separated

Starting from the propagation law of partially coherent light, the focusing properties of twisted Gaussian Schell-model (TGSM) beams passing through an optical system consisting of an aperture lens or through a system consisting of a separated aperture and lens are studied. The propagation expressions for focused TGSM beams have been derived. Our main attention is focused on the effect of the coherence of partially coherent light, the twist parameter and the distance between the aperture and lens on the focusing properties of TGSM beams. Numerical calculation results are given to illustrate how the coherence of partially coherent light, the twist parameter and the distance between the aperture and lens affect the axial irradiance in the focused field.     

扩展光源的时间和空间相干性效应分析

在干涉仪不同支路臂中分别加入透明光学层,将扩展光源入射到迈克尔逊干涉仪,观察光场的时间和空间相干现象,发现2种情况下出射光的时间和空间相干包络极值位置发生错位现象。论证了不同支路臂中的光学层可破坏干涉场中的光波相干特性,从而导致时间和空间相干性出现超前或滞后的空间位置互易效应。利用该效应,在2个入射光源条件下,可以得到一种测量光学样品的几何厚度和折射率的实验途径,并给出了相关的计算公式。     

Coherence-vortex lattice formed via Mie scattering of partially coherent light by several dielectric nanospheres

We previously demonstrated that Mie scattering of stationary partially coherent light by dielectric spheres generates coherence vortices. In this Letter, we demonstrate that a lattice of coherence vortices can be generated by Mie scattering of partially coherent electromagnetic waves by a system of three coplanar dielectric spheres. Spontaneous coherence-vortex creation and destruction is observed in our computer modeling of this system.     

Propagating a partially coherent radially polarized beam through aligned and misaligned ABCD optical systems

In the present work the propagation of a partially coherent radially polarized beam through aligned and misaligned ABCD optical systems is discussed. The elements of the beam coherence-polarization matrix for a partially coherent radially polarized beam propagating through these systems are derived for the first time. Using the derived analytical results the intensity distribution of the focused partially coherent radially polarized beam after a low-NA lens is investigated. It is shown that the coherence of the light source affects the beam intensity profile at the focal plane significantly, while for the given coherence of the light source the focal length of the used lens does not affect the beam intensity profile at the focal plane. This is consistent with the case of a partially coherent Hermite-Gaussian beam, as expected.     

Analytic design of an anamorphic optical system for generating anisotropic partially coherent Gaussian Schell-model beams

The analytic design of anamorphic optical system for transforming the coherent Gaussian beam of a He–Ne laser to a partially coherent Gaussian Schell-model beam with an anisotropic cross-section and an anisotropic degree of coherence is described. Design equations are formulated and some design examples are presented.     

Single-atom-response to a Partially Coherent Intense Laser Field

Ｓｉｎｇｌｅ┐ａｔｏｍ┐ｒｅｓｐｏｎｓｅｔｏａＰａｒｔｉａｌｙＣｏｈｅｒｅｎｔＩｎｔｅｎｓｅＬａｓｅｒＦｉｅｌｄＨＵＳｕｘｉｎｇＸＵＺｈｉｚｈａｎ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｐｔｉｃｓａｎｄＦｉｎｅＭｅｃｈａｎｉｃｓ，ＣｈｉｎｅｓｅＡｃ...     

Spatial statistics of a partially coherent wave in a randomly inhomogeneous cubic medium

The spatial statistics of a partially coherent light wave in a randomly inhomogeneous medium is considered on the basis of perturbation theory. The equations for the spatial coherence function of the light wave in a nonlinear irregular medium were solved. The variation in the fluctuation field dispersion, in its amplitude and phase, as well as the behavior of the radius of spatial correlation for various perturbations of the incident radiation, were investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 27, No. 1, pp. 56–64, January, 1984.     

用于实现散射介质中时间反演的数字相位共轭的相干性

抑制散射介质对光的散射,调控光在散射介质中的传输,是光通信、生物光子学、光镊等领域的重要课题.设计并实现了基于宽谱光源和数字相位共轭的可调控光在散射介质中传输的时间反演实验系统.实验获取了不同相干长度下物光和参考光束之间的光程差与干涉图样、相位图及时间反演信号之间的关系,分析了光源相干性对调控光在散射介质中传输的影响.实验结果表明,基于宽谱光源的相干特性和数字相位共轭技术,通过调节光程差能选择性获取同一散射角度及相同传输路径的光束的相对相位,再利用空间光调制器对参考光束进行调控,实现光束的反向传播,从而选择性实现对同一散射角度及相同传输路径的光的时间反演.     

Lensless imaging with partially coherent light

Based on the fourth-order correlation of light, lensless imaging with incoherent or partially coherent light is investigated theoretically by use of classical optical coherence theory. A novel lensless optical system for implementing imaging is proposed. The visibility and quality of the image are influenced by the coherence and transverse size of the light source. The results suggest useful imaging applications in x-ray, gamma-ray, or other wavelengths where no effective lens is available, and they have potential applications in optical metrology and holography.     

Diffractive optical elements with a double identical microstructure for determination of statistical parameters of random phase objects

Physical processes of interference pattern formation in partially coherent and coherent optical systems containing special diffractive optical elements with a double identical microstructure are studied in the case when a thin scattering object is present in the optical system. Methods for determining the spatial coherence function of the light field, the autocorrelation function of transmission of random phase screens, and the statistical parameters of the screens are considered.