Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
Material Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Science. 2020 May 15;368(6492):763-767. doi: 10.1126/science.aba9192.
Applications that use the orbital angular momentum (OAM) of light show promise for increasing the bandwidth of optical communication networks. However, direct photocurrent detection of different OAM modes has not yet been demonstrated. Most studies of current responses to electromagnetic fields have focused on optical intensity-related effects, but phase information has been lost. In this study, we designed a photodetector based on tungsten ditelluride (WTe) with carefully fabricated electrode geometries to facilitate direct characterization of the topological charge of OAM of light. This orbital photogalvanic effect, driven by the helical phase gradient, is distinguished by a current winding around the optical beam axis with a magnitude proportional to its quantized OAM mode number. Our study provides a route to develop on-chip detection of optical OAM modes, which can enable the development of next-generation photonic circuits.
应用光的轨道角动量（OAM）有望提高光通信网络的带宽。然而，不同 OAM 模式的直接光电流检测尚未得到证实。大多数关于电磁场电流响应的研究都集中在与光强度相关的效应上，但相位信息已经丢失。在这项研究中，我们设计了一种基于二碲化钨（WTe）的光电探测器，其电极几何形状经过精心设计，便于直接表征光的 OAM 的拓扑电荷。这种轨道光电流效应由螺旋相位梯度驱动，其特点是电流围绕光束轴缠绕，其大小与 OAM 模式数成正比。我们的研究为开发光 OAM 模式的片上检测提供了一种途径，这可以促进下一代光子电路的发展。
