  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-Perot 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.
