Near orthogonal launch of SPR modes in Au films.

We report the excitation of a surface plasmon resonance (SPR) close to the orthogonal axis of a gold (Au) film on borosilicate glass. Direct spectroscopic measurement of SPR shifts using different liquids are made at ∼5° incidence within a reflection spectrophotometer. The proposed mechanism to establish coupling and plasmon localization is the scattering of light able to penetrate across the film at the interfaces.