Dynamics and dephasing of plasmon polaritons in metallic photonic crystal superlattices: Time- and frequency-resolved nonlinear autocorrelation measurements and simulations

We present time- and frequency-resolved nonlinear autocorrelation measurements of polaritonic eigenstates in gold nanowire photonic crystal superlattices on a dielectric waveguide layer. The measurements show a complex behavior of the third-harmonic signal. The spectrum consists of several components with different intensities and time dynamics. Simulations based on a simple model, where the polaritonic eigenmodes are described by damped Lorentzian oscillators, show excellent agreement of time- and frequency-resolved data with the experiments. The simulations show that the superlattice structure leads to a strong modification of the polariton dynamics and prolonged dephasing times up to 60 fs compared to a simple lattice structure.