Near-field imaging of surface-plasmon vortex-modes around a single elliptical nanohole in a gold film

被引：9

作者：

Triolo, Claudia ^{[1
]}

Savasta, Salvatore ^{[1
,2
]}

Settineri, Alessio ^{[1
]}

Trusso, Sebastiano ^{[3
]}

Saija, Rosalba ^{[1
]}

Agarwal, Nisha Rani ^{[4
]}

Patane, Salvatore ^{[1
]}

机构：

[1] Univ Messina, Dipartimento Sci Matemat & Informat, Sci Fis & Sci Terra, Messina, Italy

[2] RIKEN, Cluster Pioneering Res, Theoret Quantum Phys Lab, Wako, Saitama 3510198, Japan

[3] CNR, IPCF, Messina, Italy

[4] Univ Ontario Inst Technol, Fac Sci, Nanoimaging & Spect Lab, Oshawa, ON, Canada

来源：

SCIENTIFIC REPORTS | 2019年 / 9卷 / 1期

关键词：

ORBITAL ANGULAR-MOMENTUM; OPTICAL MICROSCOPY; THIN-FILMS; LIGHT; APERTURE;

D O I：

10.1038/s41598-019-41781-2

中图分类号：

O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];

学科分类号：

07 ; 0710 ; 09 ;

摘要：

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. 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).

引用

页数：9

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