Cascaded plasmon resonant field enhancement in nanoparticle dinners in the point dipole limit

摘要

Cascaded field enhancement in silver dimer nanostructures is investigated using a dipole-dipole interaction model. Field enhancement spectra are evaluated as a function of the particle size difference and inter-particle spacing. We observe three distinct regimes of cascaded field enhancement: hindered cascading, multiplicative cascading, and the ultimate-cascading limit, depending on the dimer interaction strength. Multiplicative cascading at small inter-particle spacing leads to analytic expressions for the ultimate internal and external field enhancement factors. For silver dimers in a host with index 1.5, we obtain a maximum internal field enhancement of 2.9 × 10~3, a factor of 75 larger than that of an isolated silver nanoparticle.