Some features of plasmonic eigenmode nanolocalization in inhomogeneous metal-dielectric-metal slot waveguides

We show that transverse local narrowing of metal-dielectric-metal (MDM) plasmonic slot waveguide can squeeze plasmon mode in transverse direction (along the slot) up to several tens of nanometers. We consider the two types of narrowing: step-wise and smooth and calculate the structure and dispersion of 2D plasmonic eigenmodes in both cases. We also find the minimal possible scales of the plasmon nanolocalization.