Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 23: Symposium: Ultrafast Nanooptics III
O 23.5: Talk
Tuesday, March 27, 2007, 12:15–12:30, H38
Nanoscale force manipulation in the vicinity of a metal nanostructure — C. Spindler1, T. Brixner1, J. Carcía de Abajo2, and •W. Pfeiffer3 — 1Physikalisches Institut, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany — 2Instituto de Optica, Serrano 121, 28006 Madrid, Spain — 3Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, 33516 Bielefeld, Germany
The tight focus of Gaussian beams is commonly used to trap dielectric particles in optical tweezers. The corresponding field distribution generates a well-defined trapping potential that is only marginally controllable on a nanometer scale. Here we investigate the influence of a metal nanostructure that is located in the vicinity of the trapping focus on the trapping potential by calculating the corresponding field and force distributions. Even for an excitation wavelength that is tuned far from the plasmonic resonance of the nanostructure the trapping potential is significantly altered by the presence of the nanostructure. For the given nanostructure, i.e. a ring of spheres that is illuminated in axial direction, a stronger localization of the focus in all directions is observed. The superposition of this non-resonant Gaussian field with a planar wave illumination that is tuned on the plasmonic resonance gives a handle to modify the trapping potential. Polarization and intensity of the resonant illumination allows modifying the equilibrium position of the trapping potential providing thereby means to steer dielectric particles with nanometer precision.