Regensburg 2013 – scientific programme

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MI: Fachverband Mikrosonden

MI 10: Scanning Probe Microscopy

MI 10.5: Talk

Thursday, March 14, 2013, 10:45–11:00, H5

k-space Imaging of the Eigenmodes on a Sharp Gold Taper for Near-field Scanning Optical Microscopy — •M. Esmann, B. B. da Cunha, S. F. Becker, J. H. Brauer, P. Gross, and C. Lienau — Carl von Ossietzky Universität, 26111 Oldenburg, Germany

Adiabatic nanofocusing of surface plasmon polaritons on tapered metallic waveguides bears great potential as a novel method for apertureless near-field scanning optical microscopy (NSOM) [1,2]. Plasmon polariton wavepackets are launched on a grating-coupler and ideally come to a complete halt at the taper apex where a single point-dipole like light source is formed. This however only holds for the lowest rotationally symmetric eigenmode of the taper [3]. Higher modes that are also excited on the coupler may disturb the imaging process as they radiate into the far field before reaching the taper end. Thus, they only contribute to background signals.

We have therefore developed and implemented a k-space imaging technique to analyze the different eigenmodes emitted from tapered metallic nanowaveguides. Higher order eigenmodes in the emission of adiabatically nanofocused plasmon polariton modes on ultrasharp gold tapers are identified and filtered. Our approch allows us to use the spatial symmetry of the re-radiated light as an indicator for the tip-sample coupling and presents a step forward towards background-free NSOM imaging with ultrahigh resolution.

[1] M. I. Stockman, Phys. Rev. Lett. 93, 137404 (2004)

[2] S. Schmidt et al., ACS Nano 6, 6040 (2012)

[3] J. C. Ashley et al., Surf. Science 41, 615 (1974)