Elettra-Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy.
Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia.
Nat Commun. 2017 Apr 5;8:14971. doi: 10.1038/ncomms14971.
Optical vortices are currently one of the most intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM), have been successfully utilized in the visible and infrared in a wide variety of applications. Moving to shorter wavelengths may open up completely new research directions in the areas of optical physics and material characterization. Here, we report on the generation of extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of OAM. From a basic physics viewpoint, our results help to resolve key questions such as the conservation of angular momentum in highly nonlinear light-matter interactions, and the disentanglement and independent control of the intrinsic and extrinsic components of the photon's angular momentum at short-wavelengths. The methods developed here will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules and violation of dipolar selection rules in atoms.
光学涡旋是目前光学领域研究最集中的课题之一。这些携带轨道角动量（OAM）的光束已经在可见光和红外光中成功应用于各种领域。向更短的波长移动可能会在光学物理和材料特性领域开辟全新的研究方向。在这里，我们报告了具有飞秒持续时间和可控 OAM 的极紫外光涡旋的产生。从基础物理的角度来看，我们的结果有助于解决关键问题，例如高度非线性光物质相互作用中的角动量守恒，以及在短波长下光子角动量的内在和外在分量的解缠和独立控制。这里开发的方法将允许测试一些最近提出的概念，例如 OAM 诱导的二色性、有机分子中的磁开关以及原子中偶极选择定则的违反。
