title: Amplification of surface plasmon polaritons in the presence of nonlinearity and spectral signatures of threshold crossover.
abstract: We describe the effects of nonlinearity on propagation of surface plasmon polaritons (SPPs) at an interface between a metal and an amplifying medium of the externally pumped two-level atoms. Using Maxwell equations we derive the nonlinear dispersion law and demonstrate that the nonlinear saturation of the linear gain leads to formation of stationary SPP modes with the intensities independent from the propagation distance. Transition to the regime of stationary propagation is similar to the threshold crossover in lasers and leads to narrowing of the SPP spectrum.
authors.affiliation: Centre for Photonics and Photonic Materials, Department of Physics, University of Bath, Bath BA2 7AY, UK.
authors.forename: A
authors.initials: A
authors.lastname: Marini
authors.forename: A V
authors.initials: AV
authors.lastname: Gorbach
authors.forename: D V
authors.initials: DV
authors.lastname: Skryabin
authors.forename: A V
authors.initials: AV
authors.lastname: Zayats