Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 26: Plasmonics and nanooptics II

O 26.1: Talk

Tuesday, March 27, 2012, 10:30–10:45, MA 005

Evolutionary optimization of plasmonic nano antennas — •Thorsten Feichtner, Oleg Selig, Markus Kiunke, and Bert Hecht — Nano-Optics & Biophotonics Group, Experimentelle Physik 5, Physikalisches Institut, Wilhelm-Conrad-Röntgen-Center for Complex Material Systems, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

Various aspects of light-matter interaction can be optimized by means of plasmonic nanoantennas. This includes excited-state lifetime of antenna-based super emitters as well as spectral and directional aspects of the emitted light. So far the design of elementary nano-antennas was inspired by radio-frequency (rf-) technology.

However, at optical frequencies material properties and experimental settings need to be re-considered, so alternative antenna designs can optimize certain aspects of light-matter interaction. In order to find such optimized designs we use a checkerboard-type array of gold cubes. We show that evolutionary optimization can be used to find unexpected antenna geometries that optimize a desired quantity, such as the near-field intensity enhancement, yielding a performance that surpasses that of a conventional rf-based optical antenna design and demonstrate, that this system can be used to achieve more complex functionalities, such as a rotation of the polarization from far field to near field by 90° while maintaining a 1000-fold intensity enhancement. Additionally we identify a new but simple structure combining split ring and dipolar antenna features resulting in enhanced near fields compared to the known dipolar nano antennas.