Electromagnetic modeling of surface plasmon resonance with Kretschmann configuration for biosensing applications in a CMOS-compatible interface
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Surface Plasmon Resonance (SPR) is a wave phenomenon occurring at an interface between a dielectric and a metal. SPR has applications in label-free biodetection systems, where advances in microfabrication techniques are fostering the development of SPR-based labs-on-a-chip. This work presents a numerical analysis for the excitation of SPR using Kretschmann's configuration. With a SiO2 prism, an Au metal layer, and water as the dielectric, the system is made to be compatible with a post-CMOS microfabrication process. The results obtained from both theory and software simulation show that for a light source at 633 nm, a 50 nm thick Au film is optimal, with the reflectivity falling to a minimum of ~2% at an angle of ~68.5°, due to maximum electromagnetic SPR coupling. Simulations with a Ti adhesion layer were also performed, showing a negative effect by increasing to ~17% the minimum reflectivity when SPR is achieved, thus reducing the dynamic range of the signal captured by the system's photodetector. SPR biosensors work by monitoring changes on the refractive index close to the SPR interface, these changes were simulated showing that a change of ~10-4 RIU on the dielectric medium produces a ~0.01°change in the SPR angle. These results will facilitate the physical implementation of label-free biosensing platforms with a CMOS image sensor (CIS) photodetection stage. © 2013 Copyright SPIE.