Photoluminescence modification in self-assembled fluorescent 3D photonic crystals

We report modification of photoluminescence by a 3D photonic crystal fabricated using fluorescent polystyrene microspheres by the process of self-assembly. We demonstrate the photoluminescence (PL) modification from self-assembled 3D photonic crystals fabricated using fluorescent polystyrene (PS) spheres. The refractive index contrast in this system is ~ 0.57, which is quite small. The modification is observed in the first order photonic bandgap that occurs in these systems. The simulated band structure of the photonic crystal shows a bandgap between the first and second bands in the LU direction. This first order bandgap lies in the red region of the visible spectrum. Experimentally, the bandstucture is studied by performing angle dependent reflectivity. We found good agreement between the simulated band structure and the one obtained from reflectivity. The dye infiltrated into the PS microspheres emits into the bandgap of the photonic crystal. As a result of the reduced number density of states within the bandgap, the radiative decay rate is slowed down. This modification in the radiative decay rate was studied using both steady state and time resolved PL measurements. The steady state photoluminescence spectrum of the dye overlaps with the first order band gap of the photonic crystal. Using time resolved photoluminescence measurements, we report a 10% increase in the spontaneous emission lifetime.