Darmstadt 2008 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 55: Poster Laseranwendungen

Q 55.9: Poster

Donnerstag, 13. März 2008, 16:30–19:00, Poster C2

Polarization effects on metal edges — •Pavel Marchenko, Susanne Quabis, Ulf Peschel, and Gerd Leuchs — Max Planck Research Group, Insitute of Optics, Information and Photonics, University Erlangen-Nuremberg, Günther-Scharowsky-Str. 1 / Bau24, 91058 Erlangen

To image the intensity distribution of laser beams the so-called "knife-edge" method can be applied. The principle is to move the spot across differently oriented metal edges and reconstruct the intensity distribution by analyzing the slope of the photocurrents. But at nanoscale dimensions the modification of the electric field by the metal edge cannot be neglected, so in general the reconstruction of a strongly focused beam is not possible any more. However, understanding the mechanisms of how various parameters (wavelength, metal properties, input polarization) influence this field modification offer a way to overcome this problem.

In our experiment linearly, radially and azimuthally polarized beams at 532, 633 and 780 nm are focused by a high numerical aperture onto a sample. The sample is a p-i-n photodiode covered with metal objects consisting of an Zn/Au alloy with various mixing ratios. We move the spot over the metal edges and for each one record the photocurrent as a function of the position.

The measurements reveal "push" and "pull" effects the metal edge exerts on the field where the direction of the polarization vector plays an important role. Moreover, we can determine conditions where these effects compensate.