Stable spatial plasmon solitons in IMI waveguides with gain and loss

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. 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. However, SPP solitons reported in the above work demonstrate substantial instabilities. Here the authors consider a thin metal stripe surrounded by insulators (IMI waveguide), where SPPs at the two inter faces are weakly coupled. Dielectric at one of the interfaces is assumed active and at the other is passive.