Enhancement of optical properties of nanoscaled objects by metal nanoparticles

We provide a simple analytical model for the modification of optical properties of active molecules and other objects when they are placed in the vicinity of metal nanoparticles of subwavelength dimensions. Specifically, we study the enhancement of optical radiation, electroluminescence, and photoluminescence absorbed or emitted by these objects. 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 Ag nanospheres embedded in a GaN dielectric, we show that enhancement for each case depends strongly on the nanoparticle size-enabling optimization for each combination of absorption cross section, original radiative efficiency, and separation between the object and metal sphere. The enhancement effect is most significant for relatively weak and diluted absorbers and rather inefficient emitters that are placed in close proximity to the metal nanoparticles. (C) 2009 Optical Society of America