10:45 〜 11:15
▲ [13a-2C-6] [JSAP-OSA Joint Symposia 2015 Invited Talk] Manipulating Focusing and polarizing in Plasmonic Nanostructures
キーワード：surface plasmon polaritons, focusing,scanning near-field optical microscopy,Archimedes' spiral structure
Surface plasmon polaritons (SPPs) have shorter wavelengths and stronger field enhancement, confined to the dielectric-metal interface, in comparison with light and have been widely used in nano-optics, resonance sensing and imaging, including surface plasmon focusing. However, the low conversion efficiency and high propagation loss of SPPs limit its use. Controlling the propagation direction of SPPs by using nanostructures on metal surfaces is important. The manipulating of the focusing and polarization in plasmonic nanostructures is the key problem.
Here, we fabricated a spiral nanostructure on the Au film by using focused ion beam etching, which is used as a plasmonic circular polarization analyzer. By designing the relative orientation of two nano-apertures in the spiral structural unit, the propagation direction of the surface plasmon polaritons excited by circularly polarized light of opposite handedness can be controlled. Therefore, the spiral structure could be used to accurately determine the chirality of the excited circularly polarized light. Based on the results of scanning near-field optical microscopy (SNOM), the obtained circular polarization extinction ratio of this structure was above 500. This structure shows advantages of flexible detecting size and a very wide spectrum.
Further, by varying the chirality of the incident circularly polarized light and the spiral structure, we theoretically and experimentally studied the focusing properties of the Archimedes spiral structures. We found that in addition to the chirality of the incident light and the spiral structure, the pitch of the spiral structure and the wavelength of excited light also influence the surface plasmon field. By using a phase analysis and a FDTD simulation, we calculated the electric field and phase distribution in different spiral structures. A near-field vortex mode with spin-dependent topological charges was obtained. The SNOM measurements verified the theory and simulation.
Here, we fabricated a spiral nanostructure on the Au film by using focused ion beam etching, which is used as a plasmonic circular polarization analyzer. By designing the relative orientation of two nano-apertures in the spiral structural unit, the propagation direction of the surface plasmon polaritons excited by circularly polarized light of opposite handedness can be controlled. Therefore, the spiral structure could be used to accurately determine the chirality of the excited circularly polarized light. Based on the results of scanning near-field optical microscopy (SNOM), the obtained circular polarization extinction ratio of this structure was above 500. This structure shows advantages of flexible detecting size and a very wide spectrum.
Further, by varying the chirality of the incident circularly polarized light and the spiral structure, we theoretically and experimentally studied the focusing properties of the Archimedes spiral structures. We found that in addition to the chirality of the incident light and the spiral structure, the pitch of the spiral structure and the wavelength of excited light also influence the surface plasmon field. By using a phase analysis and a FDTD simulation, we calculated the electric field and phase distribution in different spiral structures. A near-field vortex mode with spin-dependent topological charges was obtained. The SNOM measurements verified the theory and simulation.