Cascaded Second-order Surface Plasmon Solitons due to Intrinsic Metal Nonlinearity

TL;DR

This paper theoretically and numerically demonstrates the formation of cascaded second-order surface plasmon solitons at metal-dielectric interfaces, highlighting their non-diffractive propagation and potential for advanced plasmonic applications.

Contribution

It introduces the concept of cascaded second-order surface plasmon solitons driven by intrinsic metal nonlinearity, supported by finite element modeling and theoretical analysis.

Findings

Confirmed soliton formation at metal-dielectric interfaces.

Demonstrated non-diffractive propagation over 100 μm.

Showed benefits of phase-matched plasmon-solitons for stable propagation.

Abstract

We theoretically show the existence of cascaded second-order surface plasmon solitons propagating at the interface between metal and linear dielectric. Nonlocal multipole nonlinearities originating from free conduction electron plasma of a metal lead to strong interaction between co-propagating surface plasmon polariton beams at fundamental and second harmonic frequencies. Finite element numerical modelling for effective two-dimensional medium explicitly demonstrates the solitons formation, confirming the theoretical results. The non-diffractive regime of propagation has been demonstrated at silica/silver interface for 5{\lambda} wide surface plasmon polariton beams with the loss-limited propagation distance of the order of 100 um for the 750/1550 nm wavelengths pair. Plasmon-soliton formation in the phasematched conditions has been shown to be beneficial for nondiffractive surface plasmon polariton propagation.