Scatter from tilted-columnar birefringent thin films: observation and measurement of anisotropic scatter...

We show that the angular distribution of scattered light (haze) from tilted-columnar birefringent thin films is highly anisotropic. When a narrow laser beam is incident normally upon a substrate coated with a tilted-columnar film, such as titania deposited at 60° to a thickness of ≈2 µm, the distribution of light scattered into the surrounding transmission and reflection air spaces has the form of one or more arcs. Scatter of light into the substrate is also highly anisotropic, and secondary scatter from the trapped substrate flux produces characteristic bright patterns that appear superposed on the coating.

When viewed in transmission the bright pattern typically consists of two strong lobes and in reflection four weaker lobes that make a cross. The various anisotropic distributions are shown to be consistent with interference of light from scattering centers that are correlated along the column direction and hence can be described as reflections from the tilted-columnar thin-film microstructure.