基于光束偏移器的光的轨道角动量分束器

Orbital angular momentum splitter of light based on beam displacer

近年来,光的轨道角动量自由度的高维度特性引起了广泛的关注.该自由度在许多科学领域得到了研究和应用,特别是在光通讯和量子信息领域.为了充分利用轨道角动量的高维特性,不同的轨道角动量态的非破坏分离成为一个最基本的要求.然而,目前已有的轨道角动量分束系统,要么在稳定性和级联拓展性方面有所不足;要么分离后的轨道角动量态的特性遭到严重破坏,无法参与进一步的相互作用过程.本文基于光束偏移器构建微型Mach-Zehnder干涉仪,设计了一个稳定且紧凑的轨道角动量分束器,实现了轨道角动量模式的非破坏分束.设计中由于只存在光束的全反射,因此理论上能量损耗为零.在微型Mach-Zehnder干涉仪中的光束经过的光学元件相同,且光束的空间偏移量较小,所以该轨道角动量分束器具有很好的稳定性.此外,由于被分开的轨道角动量态与入射的轨道角动量态具有相同的传播方向,因此该分束器具有很好的可拓展性,便于级联使用.本研究对轨道角动量这一高维自由度在光通讯等相关领域的应用有重要意义.

In recent years,the high-dimensional properties of the orbital angular momentum degree of freedom of light have attracted extensive attention.This degree of freedom has been studied and used in many scientific fields,especially in optical communication and quantum information.In order to fully utilize the high-dimensional properties of orbital angular momentum,non-destructive separation of different orbital angular momentum states has become a fundamental requirement.However,the existing orbital angular momentum beam-splitting systems either lack stability and cascade expansibility,or the properties of the separated orbital angular momentum states are seriously damaged,thus failing to participate in further interaction processes.In this work,we construct a miniature Mach-Zehnder interferometer based on the beam displacer,and design an orbital angular momentum beam splitter,thereby realizing the non-destructive beam splitting of orbital angular momentum mode.In the orbital angular momentum splitter,the theoretical energy loss is zero because there exists only total reflection of the beam.The beam in the miniature Mach-Zehnder interferometer passes through the same optical element,and the spatial deviation of the beam is small,so the orbital angular momentum beam splitter has good stability.In addition,because the separated orbital angular momentum state has the same propagation direction as the incident orbital angular momentum state,the beam splitter has good extensibility and is easy to use in cascade.Our research result is of great significance in using the orbital angular momentum as a high-dimensional degree of freedom in optical communication and other related fields.