中国物理B ›› 2020, Vol. 29 ›› Issue (6): 67301-067301.doi: 10.1088/1674-1056/ab862a

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Optical spin-to-orbital angular momentum conversion instructured optical fields

Yang Zhao(赵阳), Cheng-Xi Yang(阳成熙), Jia-Xi Zhu(朱家玺), Feng Lin(林峰), Zhe-Yu Fang(方哲宇), Xing Zhu(朱星)   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Center for Nanoscale Science and Technology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China;
    3 Collaborative Innovation Center of Quantum Matter, Beijing 100871, China;
    4 National Center for Nanoscience and Technology, Beijing 100190, China
  • 收稿日期:2020-03-03 修回日期:2020-03-31 出版日期:2020-06-05 发布日期:2020-06-05
  • 通讯作者: Feng Lin, Zhe-Yu Fang E-mail:linf@pku.edu.cn;zhyfang@pku.edu.cn
  • 基金资助:
    Project supported by the National Key R&D Program of China (Grant Nos. 2017YFA0205700, 2015CB932403, and 2017YFA0206000) and the National Natural Science Foundation of China (Grant Nos. 21790364, 11374023, 61422501, 11674012, 61176120, 61378059, 6097701, and 61521004).

Optical spin-to-orbital angular momentum conversion instructured optical fields

Yang Zhao(赵阳)1, Cheng-Xi Yang(阳成熙)1, Jia-Xi Zhu(朱家玺)1, Feng Lin(林峰)1, Zhe-Yu Fang(方哲宇)1,2,3,4, Xing Zhu(朱星)1,2,4   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Center for Nanoscale Science and Technology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China;
    3 Collaborative Innovation Center of Quantum Matter, Beijing 100871, China;
    4 National Center for Nanoscience and Technology, Beijing 100190, China
  • Received:2020-03-03 Revised:2020-03-31 Online:2020-06-05 Published:2020-06-05
  • Contact: Feng Lin, Zhe-Yu Fang E-mail:linf@pku.edu.cn;zhyfang@pku.edu.cn
  • Supported by:
    Project supported by the National Key R&D Program of China (Grant Nos. 2017YFA0205700, 2015CB932403, and 2017YFA0206000) and the National Natural Science Foundation of China (Grant Nos. 21790364, 11374023, 61422501, 11674012, 61176120, 61378059, 6097701, and 61521004).

摘要: We investigate the dynamic quantities: momentum, spin and orbital angular momenta (SAM and OAM), and their conversion relationship in the structured optical fields at subwavelength scales, where the spin-orbit interaction (SOI) plays a key role and determines the behaviors of light. Specifically, we examine a nanostructure of a Ag nanoparticle (Ag NP) attached on a cylindrical Ag nanowire (Ag NW) under illumination of elliptically polarized light. These dynamic quantities obey the Noether theorem, i.e., for the Ag nanoparticle with spherical symmetry, the total angular momentum consisting of SAM and OAM conserves; for the Ag NW with translational symmetry, the orbital momentum conserves. Meanwhile, the spin-to-orbital angular momentum conversion is mediated by SOI arising from the spatial variation of the optical potential. In this nanostructure, the conservation of momentum imposes a strict restriction on the propagation direction of the surface plasmon polaritons along the Ag NW. Meanwhile, the orbital momentum is determined by the polarized properties of the excitation light and the topography of the Ag NP. Our work offers insights to comprehend the light behaviors in the structured optical fields in terms of the dynamic quantities and benefits to the design of optical nano-devices based on interactions between spin and orbital degrees of freedom.

关键词: orbital angular momentum, spin angular momentum, spin-orbit interaction of light, silver nanowire

Abstract: We investigate the dynamic quantities: momentum, spin and orbital angular momenta (SAM and OAM), and their conversion relationship in the structured optical fields at subwavelength scales, where the spin-orbit interaction (SOI) plays a key role and determines the behaviors of light. Specifically, we examine a nanostructure of a Ag nanoparticle (Ag NP) attached on a cylindrical Ag nanowire (Ag NW) under illumination of elliptically polarized light. These dynamic quantities obey the Noether theorem, i.e., for the Ag nanoparticle with spherical symmetry, the total angular momentum consisting of SAM and OAM conserves; for the Ag NW with translational symmetry, the orbital momentum conserves. Meanwhile, the spin-to-orbital angular momentum conversion is mediated by SOI arising from the spatial variation of the optical potential. In this nanostructure, the conservation of momentum imposes a strict restriction on the propagation direction of the surface plasmon polaritons along the Ag NW. Meanwhile, the orbital momentum is determined by the polarized properties of the excitation light and the topography of the Ag NP. Our work offers insights to comprehend the light behaviors in the structured optical fields in terms of the dynamic quantities and benefits to the design of optical nano-devices based on interactions between spin and orbital degrees of freedom.

Key words: orbital angular momentum, spin angular momentum, spin-orbit interaction of light, silver nanowire

中图分类号:  (Collective excitations (including excitons, polarons, plasmons and other charge-density excitations))

  • 73.20.Mf
78.20.Bh (Theory, models, and numerical simulation) 78.67.Uh (Nanowires) 78.67.Bf (Nanocrystals, nanoparticles, and nanoclusters)