We demonstrate an ultrafast manipulation of the Rabi splitting energy Ω(R) in a metal-molecular aggregate hybrid nanostructure. Femtosecond excitation drastically alters the optical properties of a model system formed by coating a gold nanoslit array with a thin J-aggregated dye layer. Controlled and reversible transient switching from strong (Ω(R) ≃ 55 meV) to weak (Ω(R) ≈ 0) coupling on a sub-ps time scale is directly evidenced by mapping the nonequilibrium dispersion relations of the coupled excitations. Such a strong, externally controllable coupling of excitons and surface plasmon polaritons is of considerable interest for ultrafast all-optical switching applications in nanoscale plasmonic circuits.

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Ultrafast optical parametric amplifiers (OPAs) can provide, under suitable conditions, ultra-broad gain bandwidths and can thus be used as effective tools for the generation of widely tunable few-optical-cycle light pulses. In this paper we review recent work on the development of ultra-broadband OPAs and experimentally demonstrate pulses with durations approaching the single-cycle limit and almost continuous tunability from the visible to the mid-IR.

The generation of sub-optical-cycle, carrier-envelope phase-stable light pulses is one of the frontiers of ultrafast optics. The two key ingredients for sub-cycle pulse generation are bandwidths substantially exceeding one octave and accurate control of the spectral phase. These requirements are very challenging to satisfy with a single laser beam, and thus intense research activity is currently devoted to the coherent synthesis of pulses generated by separate sources. In this review we discuss the conceptual schemes and experimental tools that can be employed for the generation, amplification, control, and combination of separate light pulses. The main techniques for the spectrotemporal characterization of the synthesized fields are also described. We discuss recent implementations of coherent waveform synthesis: from the first demonstration of a single-cycle optical pulse by the addition of two pulse trains derived from a fiber laser, to the coherent combination of the outputs from optical parametric chirped-pulse amplifiers.