Directional radiation pattern of luminescent photonic crystals at frequencies near the second photonic stop band

The possibility of the directional enhancement of luminescence at frequencies near the edge of the second photonic bandgap of opal-type photonic crystals has been demonstrated both theoretically and experimentally. The directional patterns of radiation have been simulated by calculating the angular dependences of the density of optical states. The calculation results are compared to the experimental data obtained for the thin-film opals with terbium-containing complexes. Good agreement is achieved after the strong smoothing of the calculated curves; this smoothing is necessary because of the imperfection of the structure of actual samples.