Limit possible electric field in plasmon nanogap resonator

Abstract

We propose the theory of the plasmon excited in ultra-narrow plasmonic gap formed by a metal cylinder on a metal surface, that generates a huge resonant local electromagnetic field in optical frequencies. Resonance conditions are found. The maximum possible enhancement of the electric field in the nanogap is estimated as $\left|E_{max}\right|/\left|E_0\right|\propto {\left|{\epsilon }_m\right|}^3{\epsilon }_d^{-1}{\left(\Im {\epsilon }_m\right)}^{-2}$ A simple ultranarrow-gaped resonator can be used for SERS sensing and infrared spectroscopy of adsorbed molecules. We assume that a plasmonic nanogap is simplest and most straightforward way to increase flexibility as well as sensitivity of the plasmon-enhanced spectroscopes.

14 pages, 3 figures, 42 references