Studies of optical transitions related to π-conjugated polymers and laser dyes infiltrated in opal photonic crystals

We have investigated the emission properties of the laser dye: DCM, and photoinduced absorption (PA) properties of the π-conjugated polymer: DOO-PPP, in solutions which were infiltrated into porous synthetic opals. The infiltrated materials were chosen such that an overlap exists between the photoluminescence (PL) or PA spectra and the Bragg stop-band of the opal. We found that the PL spectrum of the dye-infiltrated opal shows angle-resolved energy redistribution. We observed PL enhancement at the high frequency edge of the Bragg stop-band and PL inhibition for frequencies inside the stop-band, with the same angular dispersion as that of the Bragg stop-band. A model is discussed to explain these PL changes, where the dielectric constant modulation affects the angular distribution of the dye dipole emission. Similar changes were observed in the PA spectrum of the infiltrated polymer solution, where the dielectric constant modulation affects the absorption dipole moment of long-lived photo-excitations on the polymer chains, such as triplet excitons.