Analytical model for luminescence enhancement by metal nanoparticles

We report a simple yet rigorous analytical model that adequately describes the luminescence enhancement of optical emitters that are placed in the vicinity of metal nanoparticles of sub-wavelength dimensions. Using the example of Au nanospheres embedded in the GaN dielectric, we show that enhancement 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.