Spectral and temporal modulations of femtosecond SPP wave packets induced by resonant transmission/reflection interactions with metal-insulator-metal nanocavities.

To study the dynamical optical interactions of nano-scaled metal-insulator-metal (MIM) structures in temporal-frequency domain, femtosecond surface plasmon polariton (SPP) wave packets propagate over a surface with a MIM structure. The resonance nature of the SPP-cavity interaction is reflected as strong modulations in the spectra of transmitted and reflected SPP wavepackets, which show peaks and valleys, respectively, corresponding to the MIM cavity's eigenmode. These features indicate that the MIM structure acts as a Fabry-Pérot etalon-type spectrum filter. With appropriate tuning of the resonance frequency of the cavity, one can extract a wave packet with a narrower time duration and temporally shifted intensity peak.