Paul Sievert

Near-field and far-field electric dipole radiation in the vicinity of a planar dielectric half space

We have used the full Sommerfeld integral formalism as well as an asymptotic formalism to study the near- and far-field radiation patterns of an electric dipole in the vicinity of a planar dielectric half space. We present systematic results for the polarization dependence of the radiation patterns in both half spaces and the ratio of the integrated power radiated into the two half spaces as a function of the relative refractive index as well as the dipole position. We find that the radiation patterns are highly structured and directed. Furthermore, the ratio of the integrated power increases significantly on increasing the relative refractive index, which can be exploited to enhance the sensitivity of spectroscopic studies of surface-bound molecules; however this ratio drops quickly for a dipole more than 0.2 wavelength from the interface.

Highly directional fluorescence emission from dye molecules embedded in a dielectric layer adjacent to a silver film

We report measurements on the angular radiation patterns from dye molecules embedded in a polymethyl methacrylate thin film spin-coated on a thin silver film. We systematically studied the influence of the thickness of the silver films and the thickness of the dielectric layers on the radiation pattern. We present the detailed radiation patterns over a large angular range showing highly polarized fluorescence emission coupled into the surface plasmon modes or waveguide modes. We also studied the influence of the polarization of the excitation beam on the radiation patterns. The experimental data are compared with numerical simulations using an asymptotic approach based on the Lorentz reciprocity theorem.

Angular radiation pattern of electric dipoles embedded in a thin film in the vicinity of a dielectric half space

We report measurements on the angular radiation pattern from an array of dye molecules embedded in a polymethylmethacrylate film deposited on a dielectric hemispherical lens. The radiation pattern is both highly structured and directed, with most of the power being radiated into the media having the higher refractive index. We also present a simulation of the far-field radiation pattern of a dipole embedded in a thin dielectric layer, which apparently has not been investigated before. The simulation matches the experimental results rather well.