  Biomimetic nanoengineered metamaterials called chiral sculptured thin films
(CSTFs) are attractive platforms for optical sensing because their porosity,
morphology and optical properties can be tailored to order. Furthermore, their
ability to support more than one surface-plasmon-polariton (SPP) wave at a
planar interface with a metal offers functionality beyond that associated with
conventional SPP--based sensors. An empirical model was constructed to describe
SPP-wave propagation guided by the planar interface of a CSTF--infiltrated with
a fluid which supposedly contains analytes to be detected--and a metal. The
inverse Bruggeman homogenization formalism was first used to determine the
nanoscale model parameters of the CSTF. These parameters then served as inputs
to the forward Bruggeman homogenization formalism to determine the reference
relative permittivity dyadic of the infiltrated CSTF. By solving the
coresponding boundary-value problem for a modified Kretschmann configuration,
the characteristics of the multiple SPP modes at the planar interface were
investigated as functions of the refractive index of the fluid infiltrating the
CSTF and the rise angle of the CSTF. The SPP sensitivities thereby revealed
bode well for the implementation of fluid-infiltrated CSTFs as SPP-based
optical sensors.
