Intensity and phase sensitivities in metal/dielectric thin film systems exhibiting the coupling of surface plasmon and waveguide modes.

Abstract

In this paper, we discuss four different configurations of metal/dielectric thin films systems: surface plasmon resonance, coupled plasmon-waveguide resonance, metallic waveguide-coupled surface plasmon resonance, and dielectric waveguide-coupled surface plasmon resonance. For the waveguide-coupled surface plasmon resonance thin film systems, we explore several waveguide thicknesses that produce different resonant line shapes, including plasmon-induced transparency and waveguide-induced transparency. This paper presents a theoretical analysis and comparison of the intensity and phase sensitivities to changes in the index of refraction in a sensing layer external to the thin film system. We discuss the material parameters and the variations that led to the sensitivity variations in each thin film system. We show that when the surface plasmon polariton mode is coupled with dielectric waveguides, there is an enhancement of the sensitivity. The plasmon-induced transparency is used to increase the dynamic range of the system and shows a monotonically increasing intensity in the range of 0.4 refractive index units.