Local-field enhancement in an optical force metallic nanotrap: application to single-molecule spectroscopy

We study the local-field enhancement in a nanocavity created by optical nanomanipulation. Recently we showed that a metallic probe can modify the optical force experienced by a metallic particle and generate a material selective trapping potential. We show that the same configuration used for optical forces can be used to control both in magnitude and tune the local-field enhancement around the particle at resonance. The spatial resolution and material selectivity of this technique, allied to its capability to manipulate particles at the nanometric level, may offer a new and versatile way to achieve surface-enhanced Raman scattering spectroscopy at the single-molecule level.