Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Posters: Plasmonics, Electronic Structure and Spin-Orbit Interaction, Semiconductor and Insulator Surfaces, Nanostructures

O 37.33: Poster

Tuesday, April 1, 2014, 18:30–22:00, P2

k-space polarimetry on an adiabatic nanofocusing near-field probe — •Martin Esmann, Simon F. Becker, Jens H. Brauer, Petra Gross, Ralf Vogelgesang, and Christoph Lienau — Carl von Ossietzky Universität, 26111 Oldenburg, Germany

Adiabatic nanofocusing of surface plasmon polaritons (SPPs) propagating on tapered metallic waveguides bears great potential as a novel method for apertureless near-field scanning optical microscopy (SNOM) [1,2]. SPP wavepackets are excited on a grating-coupler and for an ideal cone-shaped waveguide come to a complete halt at the taper apex. Hence, a single point-dipole like light source is formed there. This, however, is only true for the lowest rotationally symmetric taper eigenmode [3]. Higher eigenmodes of the waveguide disturb the imaging process in SNOM as they radiate into the far field before reaching the taper end leading to unwanted background signals.

We have therefore developed and implemented a k-space imaging technique to analyse and separate contributions from the different eigenmodes [3]. Using Stokes polarimetry, we show that the symmetry of the lowest taper eigenmode gives rise to a radially polarized mode in k-space, which is clearly identified. Furthermore, we performed approach curve scans across metallic nanostructures to investigate the influence of the near-field coupling between probe and sample on the polarization dependent intensity distribution in k-space.

[1] M. I. Stockman, PRL 93, 137404 (2004) [2] S. Schmidt et al., ACS Nano 6, 6040 (2012) [3] M. Esmann et al., BJ Nano 4, 603 (2013)