Last modified: 2011-12-14

#### Abstract

The ability of sub-wavelength, gold triangles to enhance the two photon absorption cross-section of an organic dye is investigated through finite element method calculations and experimental measurements. Hexagonal arrays of gold triangles were prepared using nanosphere lithography so that their localized surface plasmon resonance (LSPR) lies at 800 nm. A dye, AF525, capable of undergoing two photon absorption at 800 nm was then spin-coated onto the gold triangles. Several films of variable-thickness AF525 were prepared, with thicknesses ranging from 30 nm to 200 nm. The gold triangles were observed to either increase or decrease the two photon absorption cross-section of AF525, depending on the thickness of the dye layer. The dependence on AF525’s two photon cross-section on its film thickness on gold triangles was predicted by finite element method (FEM) calculations. The simulations suggest the _{two photon absorption cross-section} enhancement observed was due to the gold triangles’ LSPR, and they also suggest that the decrease in _{the two photon absorption cross-section} of AF525 on the gold nanostructure is due to a complex optical reflection pattern generated by the gold triangles.