  We show how a complex Snell's law can be used to describe the refraction of
surface plasmon polaritons (SPPs) at an interface between two metals,
validating its predictions with 3-D electrodynamics simulations. Refraction
gives rise to peculiar SPP features including inhomogeneities in the waveform
and dispersion relations that depend on the incident wave and associated
material. These features make it possible to generate SPPs propagating away
from the interface with significant confinement normal to the propagation
direction. We also show that it is possible to encode optical properties of the
incident material into the refracted SPP. These consequences of metal-metal SPP
refraction provide new avenues for the design of plasmonics-based devices.
