Photonic bandgap engineering for spectral narrowing of emission in self-assembled colloidal photonic crystals

Abstract

The engineering of a well-designed passband inside the stopband of a self-assembled colloidal crystal superlattice and its effect on the steady-state emission properties of infiltrated fluorophores is reported here. The superlattice was constructed by convective self-assembly of slabs of silica spheres of two distinct diameters. This resulted in an effective passband in between the two stopbands of the total photonic crystal structure as seen in transmission. Because of the passband there is a narrow spectral range with an increased density of states for photon modes. This is seen as a decrease in the suppression of emission (an enhancement of the emission) for the narrow spectral range where the effective passband manifests itself. These experiments indicate that the threshold for lasing can possibly be lowered by spectrally narrowing the emission of fluorophores infiltrated in suitably engineered self-assembled photonic crystal superlattices, and are therefore important towards the realization of efficient all-optical integrated circuits from functionalized photonic superlattices and heterostructures.