Surface Plasmon Resonance Fiber-Optic Sensors

This chapter describes that the majority of this signal is due to surface plasmon resonance (SPR) interaction with the coatings on the walls of the fiber and not due to interaction with the sulfur bonding to the retroreflecting Au coating on the end of the fiber. SPR spectroscopy has been applied to a number of analytical problems due to its high sensitivity to variations in the electronic nature of a surface. The SPR is supported in a thin metallic layer, and the chemistry of interest takes place on the side of the metal layer opposite the incident and reflected light. If the incident angle is fixed, then any perturbation due to chemical exposure at the outside surface of the metal film will appear as a variation in the surface plasmon propagation constant. Metal films that are too thick reduce or eliminate the interaction between the surface plasmons and the exterior surface of the film reducing the sensitivity.