  Via exploitation of surface plasmon polaritons (SPPs), columnar thin films
(CTFs) are attractive potential platforms for optical sensing as their relative
permittivity dyadic and porosity can be tailored to order. Nanoscale model
parameters of a CTF were determined from its measured relative permittivity
dyadic, after inverting the Bruggeman homogenization formalism. These model
parameters were then used to determine the relative permittivity dyadic of a
fluid-infiltrated CTF. Two boundary-value problems were next solved: the first
relating to SPP-wave propagation guided by the planar interface of a
semi-infinitely thick metal and a semi-infinitely thick CTF, and the second to
the plane-wave response of the planar interface of a finitely thick metallic
layer and a CTF in a modified Kretschmann configuration. Numerical studies
revealed that SPP waves propagate at a lower phase speed and with a shorter
propagation length, if the fluid has a larger refractive index. Furthermore,
the angle of incidence required to excite an SPP wave in a modified Kretschmann
configuration increases as the refractive index of the fluid increases.
