Paper: 2006 Resonant-plasmon field enhancement from asymmetrically illuminated conical metallic-probe tips

Resonant-plasmon field enhancement from asymmetrically illuminated conical metallic-probe tips

Reviews and Highlights Quantum Science Molecular and Soft-matter Ultrafast Nano-optics and Nanophotonics Mineralogy and Geochemistry

Ryan M. Roth, Nicolae C. Panoiu, Matthew M. Adams, Richard M. Osgood, Jr., Catalin C. Neacsu, and Markus B. Raschke
Optics Express 14, 2921 (2006).
DOI PDF

Optical-field enhancement and confinement for an asymmetrically illuminated nanoscopic Au tip suspended over a planar Au substrate is investigated both numerically and experimentally. The spatial field distribution of the tip-sample system was calculated using the full 3D finite-difference time-domain method. The calculation enables investigation of the effects of the substrate-tip placement, angle of incidence, and spectral response. The tip plasmon response leads to a significant (up to ∼70 times) local field enhancement between the tip and substrate. The enhancement is found to be extremely sensitive to the tip-sample separation distance. Tip-enhanced Raman scattering experiments were performed and the numerical results provide a consistent description of the observed field localization and enhancement.