A generalized model of maximizing the sensitivity in intensity-interrogation surface plasmon resonance biosensors.

Intensity interrogation of surface plasmon resonance (IISPR) biosensors possesses the greatest sensitivity beyond other interrogations and is operated at a fixed incident angle to enable real-time analysis without time delay, so that it promises excellent performance in biological/chemical detection and SPR imaging systems. Here we provide a general model to describe its sensitivity based on Lorentz equation and unveil the relation between the sensitivity and the metal thickness. This model presents the dependency between sensitivity and metal thickness, and the optimal thickness of gold layers to maximize the sensitivity in our experiment is 53 nm that agrees well in both measurement and simulation. This general model can be further applied in other intensity-interrogation SPR configurations as a design rule for sensing and imaging applications.