Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 79: Plasmonics and Nanooptics IV
O 79.2: Vortrag
Donnerstag, 3. April 2014, 16:15–16:30, TRE Ma
Helical Plasmonic Nanostructures for Strong Chiral Near-Fields — •Martin Schäferling1, Xinghui Yin1, Nader Engheta2, and Harald Giessen1 — 14th Physics Institute and Research Centers SCoPE and SimTech, University of Stuttgart, Germany — 2Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, USA
Chiral electromagnetic fields are used to probe the handedness of natural chiral objects. The strength of the chiroptical interaction can be quantified by the so-called optical chirality [1]. Plasmonic nanostructures can tailor the optical chirality of their near-fields [2]. Even achiral structures can generate chiral near-fields. However, their properties strongly depend on the phase between incident and scattered fields [3].
We numerically demonstrate that the eigenmodes of helical nanostructures generate near-fields with strong optical chirality. Our design with multiple helices optimizes simultaneously the strength of the optical chirality and the coupling to the external field. This structure exhibits non-trivial dependencies on the pitch of the helices due to coupling effects. We show that the optimum design strategy depends strongly on the size of the whole structure. These nanostructures with chiral eigenmodes are model devices for enantiomer sensors with improved sensitivity. Our design theoretically enhances the interaction with chiral molecules by almost two orders of magnitude.
[1] Y. Tang and A. E. Cohen, Science 332, 333 (2011).
[2] M. Schäferling et al., Phys. Rev. X 2, 031010 (2012).
[3] M. Schäferling et al., Opt. Express 20, 26326 (2012).