Effects of morphology and optical contrast in organic distributed feedback lasers

Optically pumped organic distributed feedback lasers, based on the same cavity geometry and polymeric active material, but patterned with different methods, are compared. In one case, the pattern is transferred into the polymer by spin coating the latter on top of a silica master. In the other case, the master is used as a mold to imprint a polymer film. The comparison shows that the imprinted structures, even though a lower quality copy of the master at morphological level, exhibit better performance. This result is checked for different laser cavities, and a qualitative explanation in terms of optical contrast is provided.