Spectral properties of self-assembled polystyrene nanospheres photonic crystals doped with luminescent dyes

• We used dye-doped polystyrene nanospheres to grow self-assembled photonic crystals.
• We have characterized the photonic crystals by Bragg-type reflection spectroscopy.
• We studied light emission of embedded dye as a function of excitation power.
• Photonic crystal and dye properties combine to yield lasing effect.

Three-dimensional ordered photonic crystals have been fabricated on solid substrates with a self-assembling method starting from a suspension of dye-doped polymeric nanospheres in water. These photonic crystals showed angle-dependent stop band for light transmission and, correspondingly, Bragg reflection peak due to the photonic crystal lattice. Polystyrene nanoparticles of 306 nm and 288 nm diameter, respectively in the case of the Rhodamine B and Fluored dye, were used to obtain self-assembled photonic crystals. They show 40% reflectance at 610 nm for Rhodamine B and 35% reflectance at 574 nm for Fluored doped materials. The size of the spheres calculated by Bragg’s law are in good agreement with those evaluated by scanning electron microscopy (SEM). The appropriate choice of sphere diameters results in an overlap between the photonic stop-band and the dye emission spectrum. The photonic crystals showed angle-dependent suppression of spontaneous emission of the dye in the wavelength range of the photonic stop band and enhancement near the band edge. In reflection geometries, spectral narrowing and directional emission, all indicative of stimulated emission, were observed from the active photonic crystal matrix. The results of laser induced emission studies on the dye doped photonic crystals are presented.