Surface plasmon resonance imaging with polarisation modulation

We report the first imaging SPR instrument that uses polarisation modulation and ellipsometric detection. This instrument achieves a good combination of both spatial and refractive index resolution in a simple optical setup. The polarisation of the incident beam is modulated and the reflected light imaged onto a high speed CMOS camera. To demonstrate sensitivity and linearity, refractive index measurements were made with solutions of known index, yielding a sensitivity of 2.0 × 10^-6 RIU. Measurements are also presented of a sample partially covered with a fluoropolymer layer to demonstrate imaging of a spatially varying refractive index.