Laser excitation induced modifications on distributed feedback microcavities using organic semiconductors

Distributed feedback (DFB) lasers can be achieved by spin-coating semiconductor polymers onto the top surface of a photoresist grating with designed periods. Optical pumping using lasers within the absorption spectrum of the polymer induced strong modification on the morphological distribution of the polymer film and consequently on the spectroscopic response of the DFB microcavities. The corresponding modification processes resulted mainly from the pump-laser-induced cross-linking of the polymer molecules, which led to the reduction in both the thickness and refractive index of the polymer layer. The location of the polymer laser was lowered from the top to the bottom surface of the DFB grating. Concise modeling on the angle-resolved tuning properties of the output spectrum of the DFB microcavity was achieved with excellent agreement with the experimental observation, which provided clear physical insights into the operation mechanisms of a DFB microcavity.