Light emission from thin opaline photonic crystals of low and high dielectric contrast

Abstract

Photoluminescence of dye molecules embedded in PMMA opaline photonic crystals and their SnS 2 replicas has been studied. The stop-band in the emission spectrum has been demonstrated. The role of a low dielectric contrast photonic crystal is to filter the emission from embedded light sources in accord with its transmission spectrum. In contrast, inverted opaline films of a higher dielectric contrast provide stronger radiation-to-emitter interaction, which feedback results in an amplification of a spontaneous emission of dye molecules at stop-band edges. The directionality diagram of the emission has been observed in both type photonic crystals. This, so-called, self-focusing effect has been tentatively assigned to the ultra-refraction of the emitted radiation at the sample boundary, which is dictated by the configuration of dispersion surfaces in the vicinity of the photonic band gap. The self-focusing has been found strongly dependent upon the frequency.