Tunable slow- and fast-light devices based on molecular-aggregate nanofilms

We study the tunability of nanofilms composed of linear molecular aggregates for slow- and fast-light performance. In order to describe a wide range of intensity field regimes, we consider a two-exciton model for the molecular aggregate where exciton creation or annihilation may occur. Our simulations show fractional delays and advancements of the order of those found in longer propagating media. This nanometric device presents two functionalities: (i) it allows the existence of slow or fast light in a different bandwidth of pulsed signals and (ii) such dual performance can be tuned by a small perturbation of the input signal amplitude for a fixed pulse temporal width. Both effects are tested under the usual presence of disorder in these molecular systems. This study concludes that a molecular-aggregate nanofilm presents a wide control of group velocity in the GHz and THz bandwidths.