Impact of high-order surface plasmon modes of metal nanoparticles on emission enhancement

We consider the impact of high-order surface plasmon modes supported by the metal nanoparticles on the efficiency enhancement of optical emission. We show that for a given emitter with certain original radiative efficiency, placing the emitter too close to the metal sphere does not always produce additional enhancement. Thus our model provides analytical treatment of the luminescence quenching and can be used to optimize both nanoparticle size and its separation from the emitter to yield maximum enhancement factor.