Thin-film-based field penetration engineering for surface plasmon resonance biosensing

Penetration depth defines the measurable range in evanescent-wave-based sensing techniques such as surface plasmon resonance (SPR). We investigate penetration depth variation implemented with dielectric layers in a SPR sensing structure. The results show that the penetration depth can be controlled to increase or decrease depending on a specific configuration. Effective medium theory was introduced to describe the field penetration in dielectric multilayer designs. Comparison was made with the field penetration of a localized SPR structure based on periodic nanowires. The penetration depth variation in response to environmental changes was also explored.