Rudolf Zentel

Experimental and theoretical studies of the emission directionality diagrams of a perylene dye covering the inner surface of three-dimensional opal-based photonic crystals with incomplete photonic bandgap are reported. Directionality diagram of emission intensity is interpreted in terms of the spontaneous emission suppression by photonic band gap and the emission enhancement due to photon focusing phenomenon. A theoretical model is based on the classical analysis of an angular distribution of the radiated power of a point dipole.

The effect of photonic bandgap interface upon the light scattering was studied in hetero-opals consisting of two opal thin films with different lattice constant. It is shown that the weak scattering regime is preserved in thin hetero-opal films. By comparing scattering spectra of single and hetero-opal films recorded under reversing angles of light incidence and detection it was demonstrated that the interface scatters stronger the light at oblique incident angles. Squeezing of the scattering diagram of hetero-opals compared to single opal films is also assigned to the interface scattering.

Summary form only given. The nanocomposite dye-polymer-opal has been prepared and its emission properties investigated to study photonic bandgap (PBG) effects. Opal samples with a periodicity of 220 nm were impregnated with Coumarin 6 dissolved in a polymer solution. Subsequently, UV radiation was used to obtain a solid polymer network in the opal voids. The insufficient refractive index contrast (RI), prevented a full photonic bandgap, however, distinct effects of the PBG structure on the dye emission were observed. The angular dispersion of the scattered light was studied by rotating the sample so that the angle between the [111] plane of opal and the beam axis (/spl theta/) could be varied between the normal and /spl theta/=40/spl deg/. The angle of detection of the scattered light was kept equal to the angle of the light incidence. Photoluminescence was recorded from the front and the back of the sample in both cases under front surface excitation.

The growth of an opal-like polymer photonic crystal (PhC) on deeply etched silicon wafers is reported. It is shown that 10 μm deep trenches, as narrow as 10 μm can be uniformly filled by self-assembly of microspheres, in a close-packed face-centered-cubic lattice. These observations are confirmed by optical reflectance measurements in the visible range, in agreement with theoretical calculations of the photonic band gap. A slight fluctuation of the lattice parameter is noticed in the case of the narrowest channels. The possibility to detach the PhC from the substrate is also demonstrated. The potential of this approach for building complex PhC-based complex architectures is discussed.

Angular-resolved photoluminescence spectra have been obtained from polymer-made opaline photonic crystals impregnated with Coumarin dye. Spectral changes with optical excitation power and the direction of detection have been analyzed. The anisotropy in the suppression of the spontaneous emission is shown to be in accord with the Bragg stop-band dispersion.