Effects of Near- and Far-Field Coupling on the Enhancement Factor of the Radiative Decay Rate of Multiple Emitters Near a Silver Nanoparticle Sphere

Using the coupled dipole method, we examined the enhancement factor of the radiative decay rate of one or multiple emitters when they are placed near a silver nanoparticle with a 10 nm radius. The simulation results indicate that the induced dipole of the central nanoparticle plays a key role in the enhancement factor of the radiative decay rate of emitters. The results between one emitter and the central nanoparticle are consistent with the previous studies. The near-field coupling among multiple emitters is important and will determine the magnitude and phase of the induced dipole of the central nanoparticle. When the magnitude of the induced dipole is much larger than those of the emitting dipoles, a high enhancement factor will be obtained, and the phase of the induced dipole is less important. When the magnitude of the induced dipole is comparable to those of emitting dipoles, the relative phase between the induced dipole and those of emitting dipoles will lead to both far-field constructive and destructive interference and result in complex profiles in the enhancement factor spectra.