Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Plasmonics and Nanooptics V: Light-Matter Interaction

O 37.2: Talk

Tuesday, March 21, 2017, 14:15–14:30, TRE Ma

Vectorial near-field coupling on the nano scale — •M. Esmann, S.F. Becker, J. Witt, G. Wittstock, R. Vogelgesang, and C. Lienau — Carl von Ossietzky Universität, 26111 Oldenburg, Germany

Dipole-dipole coupling is ubiquitous in nanoscale systems [1,2] leading to optical modes and coherent dynamics which sensitively depend on dipole configuration. To simultaneously study such systems on 5nm length scales and over a wide spectral range, we implemented a novel type of Scanning Near-Field Optical Microscope (SNOM): Grating-coupled Surface Plasmon Polaritions (SPPs) are adiabatically nanofocused [3] at the 10nm sized apex of a metallic nanotaper resulting in a bright, spatially isolated and spectrally broad nano light source, which acts as a probe for background-free near-field spectroscopy.

Here, we apply this technique to a prototypical system formed by dipolar coupling of the nanotaper apex to small 10×40nm gold nanorods. Upon systematic variation of coupling strength we find clear signatures of coupling-induced spectral shifts and broadening of plasmonic resonances with dramatic variations on few-nanometer length scales. We argue that our approach presents a fundamentally new way to interrogate dipole-dipole coupling in nanosystems in the spatial-, spectral- and temporal domain providing full access to coupling energies, mode profiles and the associated coherent dynamics.

[1] Zhang, Y. et al., Nature 531, 623 (2016). [2] Scholes, G.D., et al., Nature Chemistry 3, 763 (2011). [3] Stockman, M.I., PRL 93, 137404 (2004). [4] Esmann, M. et al., BJNANO 4, 603 (2013). [5] Becker, S.F. et al., ACS Photonics 3, 223 (2016).