  Few-layer flakes of hexagonal boron nitride were prepared by ultrasonication
of bulk crystals and agglomerated to form thin films. The transmission and
reflection spectra of the thin films were measured. The spectral dependences of
the linear and circular polarization revealed a hidden anisotropy of the films
over the whole sample area which could not be explained by the anisotropy of
the chaotically-oriented individual particles. Statistical analysis of optical
microscopy images showed a macroscopic particle density distribution with
ordering corresponding to the optical axis observed in the polarization data.
