Laser action of DOO-PPV and Rhodamine 590; a comparison

We have investigated spectral narrowing in solutions of the conducting polymer DOO-PPV and the laser dye Rhodamine 590 in two cases. A plain solution and a solution infiltrated into a single crystal opal which is a periodic array of SiO2 balls close packed in a fee lattice. We found that in the solution infiltrated single crystal opal slab the stimulated emission (SE) threshold is two orders of magnitude lower than that in plain solutions. We suggest that the observed decrease in the SE threshold is due to the increase of the optical path length in the opals.