Abstract
We explore the possibility to control the polarization state of light confined into sub-diffraction volumes by means of plasmonic optical antennas. To this aim, we describe a resonant cross antenna, constituted of two perpendicular two-wire antennas sharing the same gap, which is able to maintain the polarization state in the plane of the antenna. We also discuss how, by proper tuning of the arm length in a slightly off-resonance cross antenna, it is possible to effectively realize a nanoscale quarter-waveplate antenna. We present experimental results for the preparation of individual cross antennas by means of focused ion beam milling starting from single-crystalline Au microflakes, and finally show preliminary characterization results based on two-photon photoluminescence confocal imaging with linearly-polarized light. © 2011 SPIE.