  The morphology of a columnar thin film (CTF) of silver renders it an
effectively biaxially anisotropic continuum. CTFs of silver deposited on
one-dimensional gratings of photoresist showed strong blazing action and
asymmetrically coupled optical radiation to surface plasmon-polariton (SPP)
waves propagating only along one direction supported by either the
CTF/photoresist or the CTF/air interfaces. Homogenization of the CTFs using the
Bruggeman formalism revealed them to display hyperbolic dispersion, and the
dispersion of SPP waves was adequately described thereby.
