Local near-field optical response of gold nanohole excited by propagating plasmonic excitations

The remote excitation of a localized surface plasmons (LSP) by the propagating plasmonic excitations, i.e., propagating surface plasmons (PSP), receives increasing attention in recent years. Here, we study the local near-field optical response of the gold nanohole, which support LSP, remotely excited by the PSP (PSP-LSP) and the results show that this optical response of the gold nanohole relates to the excitation field, the local near-field optical spectra show a redshift phenomenon, but the intrinsic frequency of LSP remains invariant. We attribute this spectral redshift phenomenon of the PSP-LSP to the dominating effects of the PSP. A weak dependence of the resonant wavelength peak on the size of a nanostructure has been observed. Moreover, it is found that the dephasing time of the PSP-LSP is longer than the case directly excited by the laser field, and it presents a decreased trend with the increasing distance from the PSP launching location. The results in this work can be used to improve the efficiency of remote excitations and provide a new path to prolong the dephasing time of the enhanced resonant field.