Temporal plasmonics: Fano and Rabi regimes in the time domain in metal nanostructures

The Fano and Rabi models represent remarkably common effects in optics. Here we study the coherent time dynamics of plasmonic systems exhibiting Fano and Rabi spectral responses. We demonstrate that these systems show fundamentally different dynamics. A plasmonic system with a Fano resonance displays at most one temporal beat under pulsed excitation, whereas a plasmonic system in the Rabi-like regime may have any number of beats. Remarkably, the Fano-like systems show time dynamics with very characteristic coherent tails despite the strong decoherence that is intrinsic for such systems. The coherent Fano and Rabi dynamics that we predicted can be observed in plasmonic nanocrystal dimers in time-resolved experiments. Our study demonstrates that such coherent temporal plasmonics includes non-trivial and characteristic relaxation behaviors and presents an interesting direction to develop with further research.