Correlation between plasmon lifetime and near-field enhancement in nanoparticle-on-film systems

Abstract

Lifetime and near-field enhancement of coupled plasmonic systems have attracted increasing attention in recent years. However, the relationship between them in the coupled plasmon structure has not been systematically revealed. Here, we studied the correlation between the plasmon lifetime and near-field enhancement of the plasmonic gap mode of nanoparticle-on-film systems, which associates localized surface plasmons with propagating surface plasmons. Both proportional and inversely proportional relationships between lifetime and field enhancement can be achieved by tuning the system parameters. The lifetime can be modulated from 5.4 fs to 20.5 fs, with the near-field intensity enhancement changing from 1036-fold to 9960-fold. Furthermore, it is found that the extension of lifetime is influenced by film thickness and limited by the skin depth of 42 nm, and the near-field enhancement of the system is mostly determined by the coupling efficiency of propagating surface plasmons.