  Homogenized composite materials (HCMs) can support a singular form of optical
propagation, known as Voigt wave propagation, while their component materials
do not. This phenomenon was investigated for biaxial HCMs arising from
nondissipative isotropic dielectric component materials. The biaxiality of
these HCMs stems from the oriented spheroidal shapes of the particles which
make up the component materials. An extended version of the Bruggeman
homogenization formalism was used to investigate the influence of component
particle orientation, shape and size, as well as volume fraction of the
component materials, upon Voigt wave propagation. Our numerical studies
revealed that the directions in which Voigt waves propagate is highly sensitive
to the orientation of the component particles and to the volume fraction of the
component materials, but less sensitive to the shape of the component particles
and less sensitive still to the size of the component particles. Furthermore,
whether or not such an HCM supports Voigt wave propagation at all is critically
dependent upon the size of the component particles and, in certain cases, upon
the volume fraction of the component materials.
