Grating-coupling of surface plasmons onto metallic tips: A nanoconfined light source

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

Claus Ropers, Catalin C. Neacsu, Thilo Elsaesser, Martin Albrecht, Markus B. Raschke, and Christoph Lienau
Nano Lett. 7, 2784 (2007).
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We describe and demonstrate a new nanometer-scale broadband light source. It is based on the grating-coupled excitation of surface plasmon polaritons (SPPs) on the shaft of a sharp conical metal taper with a tip radius of few tens of nanometers. Far-field excitation of linear nanoslit gratings results in the resonant generation of SPPs traveling over more than 10 μm to the tip apex and converging to an intense radiative local light spot. Such nanofabricated tips are expected to find various applications in nanospectroscopy, overcoming problems with background illumination in apertureless microscopy.