Enhanced fields on rough surfaces: dipolar interactions among particles of sizes exceeding the Rayleigh limit

摘要: Amplified electromagnetic fields generated by a surface of finitely sized metal or dielectric particles are calculated. Regular arrays produced lithographic techniques and stochastic particle distributions that occur, e.g., in island films, discussed. Retarded dipolar interactions between the explicitly taken into account. Particles finite size considered for which dynamic depolarization radiation damping effects important. Limits validity present approach indicated. The total field from is calculated superposition: Scalar potentials characterizing single convoluted with distribution function describing positions. Hertz vector obtained single-particle convolution two-dimensional Shah representing array autocorrelation surface. A plane-wave description used, whereby transformed simple multiplication Fourier space. Cylindrical, general spheroidal, spherical shapes individual particle. Particle dipole moments self-consistent procedure. Dipolar result shifts broadening plasmon resonances, responsible local intensity enhancement. set universal curves given shift can be all sizes shapes. Extrema arise when grating orders change radiative to evanescent character. strong variation Raman enhancement angle wavelength vicinity these extrema clearly predicted Hertz-vector calculation. formalism described permits one calculate properties factors any process occurring at near As examples, calculation reflectivities s-and p-polarized excitation surface-enhanced Raman-scattering cross sections