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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2018
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/1810.04902 |
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| _version_ | 1866910646512123904 |
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| author | Triolo, Claudia Savasta, Salvatore Settineri, Alessio Trusso, Sebastiano Saija, Rosalba Agarwal, Nisha Rani Patanè, Salvatore |
| author_facet | Triolo, Claudia Savasta, Salvatore Settineri, Alessio Trusso, Sebastiano Saija, Rosalba Agarwal, Nisha Rani Patanè, Salvatore |
| contents | We present scanning near-field images of surface plasmon modes around a single elliptical nanohole in 88 nm thick Au film. We find that rotating surface plasmon vortex modes carrying extrinsic orbital angular momentum can be induced under linearly polarized illumination. The vortex modes are obtained only when the incident polarization direction differs from one of the ellipse axes. Such a direct observation of the vortex modes is possible thanks to the ability of the SNOM technique to obtain information on both the amplitude and the phase of the near field. The presence of the vortex mode is determined by the rotational symmetry breaking of the system and it can be considered the counterpart of the photonic spin Hall effect. Finite element method calculations show that such a vorticity originates from the presence of nodal points where the phase of the field is undefined, leading to a circulation of the energy flow. The configuration producing vortex modes corresponds to a nonzero total topological charge (+1). |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_1810_04902 |
| institution | arXiv |
| publishDate | 2018 |
| record_format | arxiv |
| spellingShingle | Near-field imaging of surface-plasmon vortex-modes around a single elliptical nanohole in a gold film Triolo, Claudia Savasta, Salvatore Settineri, Alessio Trusso, Sebastiano Saija, Rosalba Agarwal, Nisha Rani Patanè, Salvatore Optics We present scanning near-field images of surface plasmon modes around a single elliptical nanohole in 88 nm thick Au film. We find that rotating surface plasmon vortex modes carrying extrinsic orbital angular momentum can be induced under linearly polarized illumination. The vortex modes are obtained only when the incident polarization direction differs from one of the ellipse axes. Such a direct observation of the vortex modes is possible thanks to the ability of the SNOM technique to obtain information on both the amplitude and the phase of the near field. The presence of the vortex mode is determined by the rotational symmetry breaking of the system and it can be considered the counterpart of the photonic spin Hall effect. Finite element method calculations show that such a vorticity originates from the presence of nodal points where the phase of the field is undefined, leading to a circulation of the energy flow. The configuration producing vortex modes corresponds to a nonzero total topological charge (+1). |
| title | Near-field imaging of surface-plasmon vortex-modes around a single elliptical nanohole in a gold film |
| topic | Optics |
| url | https://arxiv.org/abs/1810.04902 |