An imaging surface plasmon resonance sensor using polarisation modulation

We describe an imaging SPR instrument that combines the inherent sensitivity of ellipsometric detection methods with the multiplexing ability of camera-based systems. Our approach is to electronically scan the input linear polarisation with the aid of a Faraday rotator and search for the minimum intensity transmitted through an output polariser held at a fixed azimuthal angle. The input polarisation angle at which this occurs is very sensitive to the surface plasmon resonance conditions. Single channel experiments with salt solutions of known refractive index indicate a standard deviation due to noise of 1.7 × 10−6 RIU. Imaging measurements are demonstrated with a patterned sensor and show a similar noise performance over a measurement range of 0.01 RIU and a potential 128 × 48 channels.