  Propagation of light through a uniaxial material is studied using field
theoretical methods. The materials is modeled by cubic lattice of oriented
classical Lorentz oscillators. A two-step coarse graining approach is applied.
At the bulk level, excitations of the coupled light-matter system, or
polaritons, are described by a Proca-type equation for massive vector bosons.
On the microscopic level, multiple scattering is used to relate the sub-luminal
speed of the polaritons to the polarizability of the Lorentz oscillators. For
each direction of propagation of the polaritons, three independent
polarizations exist, consistent with the integer spin of massive vector bosons.
Reflection and refraction are calculated by imposing the requirement of a
uniform gauge for the electromagnetic vector potential across the interface of
the uniaxial molecular material and vacuum. Reflectance spectra near the
resonance frequency are calculated. The spectra feature a characteristic
minimum in middle of the reflection band, in agreement with experiment. An
incident unpolarized light beam is predicted to refract into three different
rays. The model supports surface bound excitations and predicts a Goos-Haenchen
shift of the reflected beam upon reflection of light incident from vacuum onto
the material.
