A theory is developed which describes the optical properties of fractal clusters (i.e. of aggregates of non-trivial Hausdorff dimension consisting of interacting monomer particles). It is shown that with respect to these properties fractal clusters differ significantly from both gases and condensed media. The interaction between the monomers is assumed to be dipole-dipole. The theory is based on the self-consistent field equations; it takes into account the fluctuation nature of the fractal cluster (considerable probability for approach of monomers to each other despite an asymptotically zero integral density). An expression is obtained for the linear susceptibility. Combination of the monomers with the formation of a cluster entails the splitting, shift and broadening of the monomer spectra. These changes depend strongly on the fractal (Hausdorff) dimension of the cluster but do not depend on the number of monomers in it (for a cluster of non-trivial dimension). On the other hand, the monomers partially retain their individuality and the susceptibility — its quasi-resonance nature. Broadening, like the imaginary part of the susceptibility, does not depend on dissipation in an individual monomer. It is predicted that giant Raman scattering may occur at an impurity particle fixed near one of the cluster monomers when excitation takes place in the absorption band of the cluster. The enhancement factor for the scattering is also determined by the fractal dimension. 相似文献
Study of the photophysical properties of quinoline analogs of 9-styryl and 9,10-distyrylanthracenes showed that, in contrast to the case of 9-[-(2-quinolyl)vinyl]anthracene, the intramolecular geometrical relaxation process plays a decisive role in the formation of the excited state of 9,10-di-[-(2-quinolyl)vinyl]-anthracene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 824–829, June, 1987. 相似文献
We have employed a parallelized 3D FDTD (finite-difference time-domain) solver to study the electromagnetic properties of
random, semicontinuous, metal films. The structural features of the simulated geometries are exact copies of the fabricated
films and are obtained from SEM images of the films themselves. The simulation results show good agreement with the experimentally
observed far-field spectra, allowing us to also study the nonlinear moments of the optical responses for these realistic nanostructures. 相似文献
The broadband enhancement of single‑photon emission from nitrogen‐vacancy centers in nanodiamonds coupled to a planar multilayer metamaterial with hyperbolic dispersion is studied experimentally. The metamaterial is fabricated as an epitaxial metal/dielectric superlattice consisting of CMOS‐compatible ceramics: titanium nitride (TiN) and aluminum scandium nitride (AlxSc1‐xN). It is demonstrated that employing the metamaterial results in significant enhancement of collected single‑photon emission and reduction of the excited‐state lifetime. Our results could have an impact on future CMOS‐compatible integrated quantum sources.
The compensation of loss in metal by gain in interfacing dielectric has been demonstrated in a mixture of aggregated silver
nanoparticles and rhodamine 6G dye. An increase of the quality factor of surface plasmon (SP) resonance was evidenced by the
sixfold enhancement of Rayleigh scattering. The compensation of plasmonic losses with gain enables a host of new applications
for metallic nanostructures, including low- or no-loss negative-index metamaterials.
We have also predicted and experimentally observed a suppression of SP resonance in metallic nanoparticles embedded in dielectric
host with absorption.
PACS 61.46.Df; 73.20.Mf; 78.67.Bf 相似文献
Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial
(HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental
results obtained by measuring angular-dependent emission spectra of europium ions on top of different films. The results show
the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces. The results of numerical calculations
agree well with experimental data. 相似文献
We present comprehensive studies on thin diffraction lenses made of arrays of subwavelength, parallel nanoslits in a gold film. Such a nanoslit lens can operate either as a conventional convex or concave lens. The lenses can be designed to focus linearly polarized light with polarization either perpendicular (TM-lens) or parallel to the slits (TE-lens), while the orthogonal polarization diverges when passing through the lens. The designs of each lens are initially built on the dispersion relations for wave propagation through a parallel-plate waveguide. Both TM- and TE-lenses were realized experimentally, and full-wave numerical simulations fully support the experimental results. 相似文献