The fundamental mechanisms of tip-enhanced Raman spectroscopy (TERS) have been investigated, including the role of the plasmonic excitation of the metallic tips, the nature of the optical tip-sample coupling, and the resulting local-field enhancement and confinement responsible for ultrahigh resolution imaging down to just several nanometers. Criteria for the distinction of near-field signature from far-field imaging artifacts are addressed. TERS

In this article, two alternative experimental strategies for reaching light confinement at metallic nanotips are discussed. The first approach utilizes optical field enhancement to localize nonlinear optical signals at the tip end. The second approach employs surface plasmon polaritons propagating coherently along the tip shaft and converging at its apex.

Thin film properties of the set of metal-free linearly benzo-annelated porphyrazines, tetra(tert-butyl)porphyrazine (tBu-TAPH2), tetra(tert-butyl)phthalocyanine (tBu-PcH2), tetra(tert-butyl)naphthalocyanine (tBu-NpH2), and octaphenyltetraanthraporphyrazine (AnH2) were studied by laser excitation using micro-Raman and -luminescence spectroscopy. With the exception of tBu-TAPH2 all compounds are characterized by a broad absorption pattern mainly due

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 microm to the tip apex and converging to an intense radiative local light spot. Such