High-Sensitivity Electro-Optic-Modulated Surface Plasmon Resonance Measurement Using Multilayer Waveguide-Coupled Surface Plasmon Resonance Sensors

Electro-optical modulated surface plasmon resonance detection is demonstrated using the prism-coupled, angular interrogation scheme, enabled by a three-layer, metal/electro-optical dielectric layer/metal-structure sensor. The tunable waveguide-coupled surface plasmon resonance effect of the sensor is exploited to carry out the detection of glucose solutions of different concentrations. It is experimentally shown that the waveguide-coupled surface plasmon resonance angle increases linearly with the applied voltage for fixed concentration. The linear regression slope of the relation between the resonant angle and the applied voltage linearly increases with the concentration of the analyte, and is used to find the concentration changes. In contrast to the previously studied semiconductor waveguide devices, the multi-layer thin film structure made on the glass substrate is not only much easier and cheaper to fabricate but also fully compatible with the widely used prism-coupled SPR systems. Further increase in the nonlinearity of the material could also enhance the sensitivity.