  A dielectric columnar thin film (CTF), characterized macroscopically by a
relative permittivity dyadic, was investigated theoretically with the
assumption that, on the nanoscale, it is an assembly of parallel, identical,
elongated ellipsoidal inclusions made of an isotropic dielectric material that
has a different refractive index from the bulk material that was evaporated to
fabricate the CTF. The inverse Bruggeman homogenization formalism was developed
in order to estimate the refractive index of the deposited material, one of the
two shape factors of the ellipsoidal inclusions, and the volume fraction
occupied by the deposited material, from a knowledge of relative permittivity
dyadic of the CTF. A modified Newton--Raphson technique was implemented to
solve the inverse Bruggeman equations. Numerical studies revealed how the three
nanoscale parameters of CTFs vary as functions of the vapour incidence angle.
