R. Vogelgesang¹, J. Dorfmüller¹, W. Khunsin¹, C. Rockstuhl², and K. Kern¹

Talk at the 2nd International Conference on Metamaterials, Photonic crystals and Plasmonics, META'10 in Cairo, February 2010.

¹Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
²Institute of Condensed Matter Theory and Solid State Optics, Friedrich-Schiller Universität Jena,
07743 Jena, Germany

We develop a fully analytical model for the electromagnetic behavior of thin plasmonic wires, i.e., linear plasmonic antennas. It uses only the complex propagation constant of the lowest order wire mode, the reflection phase it suffers at the wire termination, its amplitude, and the amplitude of higher order contributions as adjustable parameters. Our model successfully predicts measured and simulated data in full detail: emission patterns, nearfield optical amplitudes and phases, as well geometric resonances.

At radio-frequencies, antenna theory is a mature and well understood topic. Assuming negligible skin depths, it successfully predicts all relevant parameters from the starting point of induced surface currents. At optical frequencies, however, electromagnetic fields penetrate substantially into the volume of metallic nanostructures., rendering classic antenna theory not applicable. Therefore, we model thin, linear plasmonic wire antennas based on the extreme opposite assumption: homogeneous volume currents.

From this starting point, we develop a theory that requires only a handful, physically motivated, adjustable parameters. Once these have been obtained, we find our model successfully predicts a large variety of properties of plasmonic antennas, such as farfield emission patterns, nearfield optical amplitudes and phases, as well geometric resonances.

REFERENCES
1. Dorfmüller, J., Vogelgesang, R., Weitz, R. T., Rockstuhl, C., Etrich, C., Pertsch, T., Lederer, F., and K. Kern,
“Fabry-Pérot resonances in one-dimensional plasmonic nano-structures,” Nano Lett., 9, 2372–2377, 2009