Particle-plasmon decay-time determination by measuring the optical near-field’s autocorrelation: influence of inhomogeneous line broadening

Abstract.A detailed analysis of the influence of inhomogeneous plasmon absorption band broadening on particle-plasmon decay-time determination by an interferometric autocorrelation method is reported. We present model calculations based on the representation of plasmons in an array of non-uniformly shaped particles by an ensemble of harmonic oscillators. Considering carefully the extent of the inhomogeneous broadening our theoretical treatment yields an unambiguous correlation between the autocorrelation function and the plasmon decay time. As an experimental example we find a plasmon decay time of 6 fs for a gold nanoparticle sample.