Plasmonic modes with long radiative lifetimes combine strong nanoscale light confinement with a narrow spectral line width carrying the signature of Fano resonances. The interplay between radiative and non-radiative lifetimes of subradiant modes critically determines their optical properties and optimal use in nanoplasmonic applications. Here, it is shown analytically and numerically with the example of a silver nanostructure that the coupling to radiation of a subradiant mode, its radiance, can be classified into three different regimes. The modulation damping is a unitless lineshape parameter which provides direct information on the radiance. In the weak coupling regime, subradiant modes are very sensitive to geometrical displacements and deformations. Strong modulation of their spectral lineshape is also observed. At critical coupling, the radiative and non-radiative decays are balanced and the electromagnetic energy stored in the mode is maximal. For larger coupling, hybridization of the modes may be observed. In general, the classification of the coupling regimes presented here provides a systematic way to choose the most adapted coupling regime for specific nanoplasmonic applications.

Date Published: 11 September 2013
PDF: 6 pages
Proc. SPIE 8809, Plasmonics: Metallic Nanostructures and Their Optical Properties XI, 88090A (11 September 2013); doi: 10.1117/12.2023325

Published in SPIE Proceedings Vol. 8809:
Plasmonics: Metallic Nanostructures and Their Optical Properties XI
Mark I. Stockman, Editor(s)