Surface-plasmon energy gaps and photoluminescence

Abstract

Excited dye molecules on a metallic grating can relax by generating surface plasmon polaritons (SPP's). These SPP's can scatter from the grating reradiating their energy as photons. For dye molecules in contact with the metal, light radiated by SPP's dominates the optical emission from the system. If the wavelength of the SPP is equal to half the pitch of the grating then the mode can Bragg reflect from the surface and an energy gap opens up in the SPP dispersion. This paper examines the effect that such an energy gap has on the emission properties of the dye. Experimentally it is found that the SPP energy gap significantly inhibits emission from the system. Numerical modeling is used to show that the modified emission spectrum is determined by the wavelength dependence of the density of available SPP states.