Light scattering from disordered overlayers of metallic nanoparticles

We develop a theory for light scattering from a disordered layer of metal nanoparticles resting on a sample. Averaging over different disorder realizations is done by a coherent potential approximation. The calculational scheme takes into account effects of retardation, multipole excitations, and interactions with the sample. We apply the theory to a system similar to the one studied experimentally by Stuart and Hall [Phys. Rev. Lett. {\bf 80}, 5663 (1998)] who used a layered Si/SiO$_2$/Si sample. The calculated results agree rather well with the experimental ones. In particular we find conspicuous maxima in the scattering intensity at long wavelengths (much longer than those corresponding to plasmon resonances in the particles). We show that these maxima have their origin in interference phenomena in the layered sample.Comment: 19 pages, 12 figure

Directional Enhancement of Spontaneous Emission in Polymer Flexible Microcavities

We report on the control of spontaneous emission in flexible polymer 1D photonic crystal cavities fabricated by spin coating having a layer of poly(9,9-dioctylfluorenyl-2,7-diyl-co-1,4-benzo-(2,1'-3)-thiadiazole) (F8BT) as an active material. The optical properties of these full-polymer photonic crystals are systematically investigated by means of polarized angular-resolved transmittance and photoluminescence spectral measurements. We demonstrate strong directional emission enhancement when the emitter is located in the defect layer and resonantly coupled to the microcavity mode. The experimental results can be successfully reproduced with different theoretical optical models