Symmetric Plasmonic Slot Waveguides with a Nonlinear Dielectric Core: Bifurcations, Size Effects, and Higher Order Modes

We study the nonlinear stationary waves propa- gating in metal slot waveguides with a Kerr-type dielectric core. We develop two independent semianalytical models to describe these waves in such waveguides. Using these mod- els, we compute the dispersion curves for about ten first modes of a nonlinear slot waveguide. For symmetric waveg- uides, we find symmetric, antisymmetric, and asymmetric higher order modes which are grouped in two families. In addition, we study the influence of the slot width on the first symmetric and asymmetric modes. We also show that the dispersion curve of the first asymmetric mode is invariant with respect to the slot width for high propagation constant values and we provide analytical approximations of this curve. Using realistic values for the optogeometric parame- ters of the structure, we are able to obtain the bifurcation at a realistic power.