Dual-polarization interferometry (DPI) is an analytical technique that probes molecular layers adsorbed to the surface of a waveguide using the evanescent wave of a laser beam.
The polarization can be switched rapidly, allowing real-time measurements of chemical reactions taking place on a chip surface in a flow-through system.
These measurements can be used to infer conformational information about the molecular interactions taking place, as the molecule size (from the layer thickness) and the fold density (from the RI) change.
DPI is typically used to characterize biochemical interactions by quantifying any conformational change at the same time as measuring reaction rates, affinities and thermodynamics.
A novel application for dual-polarization interferometry emerged in 2008, where the intensity of light passing through the waveguide is extinguished in the presence of crystal growth.