Correlation plenoptic imaging (CPI) is a light-field imaging technique employing intensity correlation measurements to simultaneously detect the spatial distribution and the propagation direction of light. Compared to standard methods, in which light-field images are directly encoded in intensity, CPI provides a significant enhancement of the volumetric reconstruction performance in terms of both achievable depth of field and 3D resolution. In this article, we present a novel CPI configuration where light-field information is encoded in correlations between position and momentum measurements, namely, points on a given object plane and points of the Fourier plane of the imaging lens. Besides the fundamental interest in retrieving the properties of position-momentum correlation, the proposed scheme overcomes practical limitations of previously proposed setups, providing higher axial homogeneity and robustness with respect to the identification of reference planes.
Microscope for X-ray orbital angular momentum imaging
光子的轨道角动量（OAM）携带在光学涡旋的波前上，由于其基本自由度，在物理研究中具有重要意义。至于与材料的相互作用，基于修改的选择规则，光学OAM被示出转移到价电子，其中单个离子被仔细地对准到涡旋的中心[Schmiegelow等人，（2016）]。我们在这里展示了一个精心设计的方式提取分布的OAM在二维X射线波场在出射面的标本的涡敏感显微镜，检测涡的倒数空间波场下游的光学涡旋。这种方法使我们能够通过一个单一的图像与超过300 $μ$ m的宽视场测量分布的拓扑电荷和OAM。在各种波长中，X射线OAM的研究特别有趣，因为它可能与预测的OAM诱导的X射线二向色性密切相关[Veenendaal et al.（2007）]。
Experimental Verification of Position-Dependent Angular-Momentum Selection Rules for Absorption of Twisted Light by a Bound Electron
我们分析了原子的多极激发与扭曲的光，即，携带轨道角动量的涡旋光场单个捕获的$^{40}$ Ca $^+$离子用作激发场的局部化和定位探针。我们驱动的$S_{1/2} \to D_{5/2}$过渡和观察不同的过渡的相对强度，取决于离子的横向位置相对于中心的涡旋光场。另一方面，计算了贝塞尔光束、贝塞尔-高斯模和高斯-拉盖尔模形式的扭曲光场的跃迁振幅。分析实验获得的跃迁振幅，我们发现与理论预测的协议在优于3%的水平。最后，我们提出了测量方案与双离子晶体，以提高在未来的实验中的涡旋模式的传感精度。
