Equivalent deflection angle of textured surfaces

The concept of optical path length enhancement is a useful tool for characterizing the effects of light trapping in thin films by providing a convenient geometrical interpretation of energy absorption. However, path length calculations cannot distinguish between absorption gains due to better antireflection versus absorption gains due to actual scattering of incident rays. We therefore introduce a similar metric of equivalent deflection angle to describe the effective scattering of light by a textured surface. This new concept provides useful information about light trapping that path length alone cannot. The paper begins with the geometrical interpretation of the metric and then demonstrates the insights derived from light scattering by a simple textured surface.