Plasmon Enhancement of Luminescence by Metal Nanoparticles

We present a simple analytical yet rigorous model that adequately describes the luminescence enhancement of optical emitters that are placed in the vicinity of metal nanoparticles of subwavelength dimensions. The theory takes into account the radiative decay of the surface plasmon mode supported by the metal nanospheres-a basic phenomenon that has been ignored in electrostatic treatment. Using the example of Au nanospheres embedded in the GaN dielectric, we show that enhancement for each case depends strongly on the original radiative efficiency of the emitter, the nanoparticle size, and the separation between the emitter and metal nanosphere. We demonstrate that strong enhancement favors the closely spaced emitters and metal nanospheres, but putting them too close to each other 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.