  A porous material was considered as a platform for optical sensing. It was
envisaged that the porous material was infiltrated by a fluid which contains an
agent to be sensed. Changes in the optical properties of the infiltrated porous
material provide the basis for detection of the agent to be sensed. Using a
homogenization approach based on the Bruggeman formalism, wherein the
infiltrated porous material was regarded as a homogenized composite material,
the sensitivity of such a sensor was investigated. For the case of an isotropic
dielectric porous material of relative permittivity $\epsilon^a$ and an
isotropic dielectric fluid of relative permittivity $\epsilon^b$, it was found
that the sensitivity was maximized when there was a large contrast between
$\epsilon^a$ and $\epsilon^b$; the maximum sensitivity was achieved at
mid-range values of porosity. Especially high sensitivities may be achieved for
$\epsilon^b$ close to unity when $\epsilon^a >> 1$, for example. Furthermore,
higher sensitivities may be achieved by incorporating pores which have
elongated spheroidal shapes.
