Nonlinear couplers with tapered plasmonic waveguides.

We suggest and demonstrate numerically that, by employing tapered waveguides in the geometry of a directional coupler, we can enhance dramatically the performance for optical switching of nonlinear plasmonic couplers operating at the nanoscale, overcoming the detrimental losses but preserving the subwavelength confinement. We demonstrate that, by an appropriate choice of the taper angle of the coupled metal-dielectric slot waveguides, we can compensate for the amplitude decrease and enhance the sharpness of the response for the switching operation.