强聚焦高阶时空涡旋的生成方法及其传播特性  

Generation and Propagation of Strongly Focused High-Order Spatiotemporal Optical Vortex

作　　者：于自强 莫德威 于飞 詹其文 陈建 Yu Ziqiang;Mo Dewei;Yu Fei;Zhan Qiwen;Chen Jian(School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;Shanghai Key Laboratory of Modern Optical System,University of Shanghai for Science and Technology,Shanghai 200093,China;The R&D Center for High Power Laser Components,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;School of Physics and Optoelectronic Engineering,Hangzhou Institute for Advanced Study,UCAS,Hangzhou 310024,Zhejiang,China)

机构地区：[1]上海理工大学光电信息与计算机工程学院,上海200093 [2]上海理工大学,上海市现代光学系统重点实验室,上海200093 [3]中国科学院上海光学精密机械研究所高功率激光单元技术实验室,上海201800 [4]国科大杭州高等研究院物理与光电工程学院,浙江杭州310024

出　　处：《光学学报》2024年第10期338-346,共9页Acta Optica Sinica

基　　金：国家自然科学基金(12274299,92050202);上海市青年科技启明星(22QA1406600)。

摘　　要：主要研究了经高数值孔径物镜强聚焦生成高阶时空涡旋的方法及高度局域时空涡旋在焦平面前后的传播特性。根据模式转换理论,对入射波包进行预处理,利用Richards Wolf矢量衍射公式仿真计算预处理后的入射波包以及经透镜强聚焦后在焦平面及焦平面前后传播的时空波包的三维时空分布,并对其强度和相位进行了分析。结果表明,强聚焦波包具有预定的高阶时空螺旋相位,且在透镜焦平面前后传播过程中,时空波包的总拓扑荷数保持不变,波包强度分布发生旋转,波包内部演化出若干个一阶时空相位奇点。Objective Photons can carry spin angular momentum(SAM)related to their polarization state and orbital angular momentum(OAM)related to their spiral phase.In recent years,spatiotemporal optical vortices(STOVs)that carry transverse OAM have gained rapidly growing interest in the field of optics due to their capacity to introduce new degrees of freedom for regulating the optical field.Current research is primarily concentrated on low-order STOVs,with limited attention given to the generation and propagation characteristics of high-order STOVs.We mainly investigate the generation of high-order strongly focused STOVs based on incident wavepacket preconditioning using mode conversion theory.Additionally,we also study the propagation characteristics of highly localized STOVs both before and after the focal plane.Methods Research has shown that when STOVs are focused by a high numerical aperture(NA)objective lens,they will experience the so-called spatiotemporal astigmatism effect similar to the focusing effect of a cylindrical lens on the Laguerre-Gaussian(LG)light field.Thus,STOVs will collapse and lose their spatiotemporal spiral phase on the focal plane of the high NA objective lens.With the understanding of such a spatiotemporal astigmatism,we preconditioned the incident wavepacket by a linear superposition of LG spatiotemporal wavepackets and then employed a high NA objective lens to focus the preconditioned incident wavepacket.The high-order STOVs on the focal plane or propagating away from the focal plane were calculated based on the Richards Wolf diffraction theory.In the simulations,it was assumed that the NA of the objective lens was 0.9,and the waist radius was set to be 0.5.Meanwhile,spatiotemporal coupling was ignored,and thus each temporal slice of the incident wavepacket was focused onto its corresponding temporal slice within the focal volume.The spatial sizes of the incident wavepackets were normalized to the pupil of the objective lens.Results and Discussions Although the third-order STOV exhibits trans

关 键 词：物理光学 轨道角动量 时空光涡旋 强聚焦 光束传播 拓扑荷数 

分 类 号：O436[机械工程—光学工程]