Generation and shaping of near-field optical vortices using plasmonic spiral and slot

• Main Authors: Huang, Wei-Lun, 黃偉倫
• Other Authors: Huang, Chen-Bin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/67207531314206507963

碩士 === 國立清華大學 === 光電工程研究所 === 100 === 　　In this work, we use finite-difference time-domain method to simulate the optical vortex phenomenon of surface plasmons. An optical vortex is characterized by its topological charge, which denotes the number of phase singularities within a 2 azimuthal rotation. There are two main factors can influence the topological charge of surface plasmon vortex: one is the geometrical charge which can determine the geometry of plasmonic spiral device, another is the spin angular momentum of the photon of the incident circularly polarized plane wave. We analyze the basic property of surface plasmon vortex distributions in space by studying the relationship between these two factors. Furthermore, we change the structure arrangement of plasmonic spiral device in a novel way that can adaptively control the intensity distributions of the surface plasmon vortex in space without changing the topological charge and the basic property of the surface plasmon vortex. 　　In the aspect of sample fabrication, we use thermal evaporation to deposit the metallic film upon to the cover glass substrate. Then we use focused ion beam to mill the micro structure of plasmonic spiral device. In the aspect of near-field measurement, we use collection mode near-field scanning optical microscope with normal incident set-up and the shear force feedback scanning method to obtain the near-field signal of surface plasmon vortex, which is generated from the plasmonic spiral device. Finally, we compare the experimental data with the simulation result. Similar phenomenon can verify the correctness of the design principle of plasmonic spiral device.