Surface Plasmon-Coupled Ultraviolet Emission of 2,5-Diphenyl-1,3,4-oxadiazole.

We studied surface plasmon-coupled emission (SPCE) of 2,5-diphenyl-1,3,4-oxadiazole (PPD) using a 20 nm aluminum film deposited on a quartz substrate. The directional SPCE UV fluorescence occurs within a narrow angle at 57° from the normal to the coupling hemicylindrical prism. This radiation is almost completely p-polarized, consistent with its origin from surface plasmons. These surface plasmons are induced by excited PPD molecules. The coupling of excited fluorophore dipoles with the aluminum is highly efficient, exceeding 50%. Different fluorescence emission wavelengths are emitted at slightly different angles on the prism, providing intrinsic spectral resolution. SPCE fluorescence on thin aluminum films can be used with many UV absorbing and emitting fluorophores.