A process comprises imagewise exposing at least a portion of a photoreactive composition to light sufficient to cause simultaneous absorption of at least two photons/thereby inducing at least one acid- or radical-initiated chemical reaction where the composition is exposed to the light, the imagewise exposing being carried out in a pattern that is effective to define at least the surface of a plurality of light extraction structures. Each one of the array of light extraction structures has at least one shape factor; the shape factor may vary across the array. At least one light extraction structure may have the geometric configuration of a truncated asphere.