Dual polarisation interferometry
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Dual polarisation interferometry (DPI) is an analytical technique in chemistry that can probe layers adsorbed to the surface of a waveguide by using the evanescent wave of a laser beam confined to the waveguide.[1]
DPI focuses laser light into two waveguides, one, the "sensing" waveguide, with an exposed surface and one to create a reference beam. A two-dimensional interference pattern is formed in the far field by combining the light passing through the two waveguides. The DPI technique rotates the polarisation of the laser to alternately excite two polarisation modes of the waveguides. Measurement of the interferogram for both polarisations allows both the refractive index and the thickness of the adsorbed layer to be calculated. The polarisation can be switched rapidly, allowing "real time" measurements of chemistry taking place on a chip surface in a flow-through system. These measurements can be used to infer structural information about the molecular interactions taking place and is typically used to characterise biochemical interactions.
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- ^ Neville J. Feeman, Louise L. Peel, Marcus J. Swann, Graham H. Cross, Andrew Reeves, Stuart Reeves, and Jian R. Lu (2004). "Real time, high resolution studies of protein adsorption and structure at the solid–liquid interface using dual polarisation interferometry". J. Phys.: Condens. Matter 16: S2493–S2496. doi:.
