Ultrafast self-action of surface-plasmon polaritons at an air/metal interface

Abstract

We investigate both theoreticaally and experimentally the nonlinear propagation of surface plasmon polaritons (SPP) on a single air/metal interface. Inspired by nonlinear dielectric waveguide theory, we analytically derive a model that describes the nonlinear propagation of SPPs, thus bridging the description of plasmonic and dielectric waveguides. The model, the numerical simulations and the experiments, which are carried out in the hundred femtosecond regime, reveal that the SPP undergoes strong ultrafast self-action which manifests itself through selfinduced absorption. Our observations are consistent with a large, bulk, third-order nonlinear susceptibility (χ(3)) of gold and provide a selfconsistent theory of self-action of SPPs at an air/metal interface. Experimentally, we find Im{χ (3)} 3×10-16 m2/V2. These findings have important implications in the nonlinear physics of plasmonics and metamaterials as they provide evidence that nonlinear absorption has a significant effect on the propagation of SPPs excited by intense optical pulses. This self-action is also expected to affect the anomalous absorption of light near subwavelength structures as well as the strength of desirable nonlinear processes such as third-harmonic generation and four-wave mixing, which will inevitably compete with nonlinear absorption.

Free‐electron Optical Nonlinearities in Plasmonic Nanostructures: A Review of the Hydrodynamic Description

“…Ultrafast plasmonic Kerr nonlinearity can substantially influence the propagation of the SPP modes at the metal/dielectric interface, particularly in the case of dielectrics lacking a strong nonlinear response . For example, it was shown both theoretically and experimentally that in this case SPPs experience prominent self‐induced absorption . Nonlinearity may lead to completely unexpected behaviour of SPPs.…”

Nonlinear optical model for strip plasmonic waveguides

“…Also, the real and imaginary components of the third-order susceptibility of thin gold layers were characterized using the z-scan method [6,7]. In another recent experiment Baron et al [8] measured the imaginary component of the third-order susceptibility for bulk gold by studying nonlinear propagation of surface-plasmon polaritons at a single air/metal interface.…”

Nanoscale nonlinear plasmonics in photonic waveguides and circuits

“…A review by the same authors [102] found that measured values of χ (3) of gold can vary by several orders of magnitude, depending on wavelength, pulse duration, or the nature of the nonlinear experiment. Most strikingly, similar measurements of the nonlinear absorption of SPPs at gold/air interfaces [169] resulted in χ (3) values which were three orders of magnitude larger. In this case, the authors excited SPPs on a gold film using asymmetric gratings, which also collected the light, as shown in Fig.…”