Abstract
We propose and experimentally demonstrate several nano-devices which are able to selectively excite optical fields using surface plasmons within the designed structures. It was the first time to our best knowledge that up to ten selective states could be excited in the near-field. On the other hand, the device is also capable of analyzing the polarization state in the near-field, especially the handedness of circular polarizations. Numerical analysis, device fabrication and optical measurement are all covered in this work. Numerical experiments suggest that up to ten selective localized surface plasmon states can be generated using excitation with different polarization states, in a device consisting of seven gold nanospheres or nanodisks. This capability can be also reproduced using a designed structure with several nano-holes on a gold film. The proposed device was fabricated using a common process involving thermally evaporated gold film and focused ion-beam milling. Optical measurements were performed with a homemade optical measurement system, which include a near-field scanning optical microscope and polarization controlling optics. Selective excitations of localized surface plasmons were experimentally verified, and shown to be capable of distinguishing the handedness of circular polarizations.