We have investigated spectral narrowing in solutions of the conducting poly
mer 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 a
rray of SiO2 balls close packed in a fee lattice. We found that in the solu
tion infiltrated single crystal opal slab the stimulated emission (SE) thre
shold is two orders of magnitude lower than that in plain solutions. We sug
gest that the observed decrease in the SE threshold is due to the increase
of the optical path length in the opals.