Stable spatial plasmon solitons in IMI waveguides with gain and loss

Surface Plasmon Polaritons (SPPs) provide one of the favored approaches to realization of on-chip photonic devices, novel imaging schemes and are a well established tool in sensing applications. While SPPs are exponentially localized in the direction perpendicular to the metal-dielectric interface by the natural boundary conditions, one should take a special care about suppression of their in-plane diffraction. An interesting alternative to various geometrical methods providing lateral confinement of SPPs is to use the concept of spatial solitons, where diffraction is suppressed by the nonlinearity induced focusing, see, e.g., [1]. Further, the spatial soliton concept can be extended by complementing the diffraction vs nonlinearity balance with the gain vs loss balance, thus completely solving the problem of the soliton decay due to linear absorption. Towards this aim, cubic Ginzburg-Landau equation has been derived for the SPPs at the boundary with active dielectric [2]. However, SPP solitons reported in the above work demonstrate substantial instabilities [2].