Abstract
A high-sensitivity surface plasmon resonance (SPR) biosensor based on the Mach–Zehnder interferometer design is presented. The novel feature of the new design is the use of a Wollaston prism through which the phase quantities of the and polarizations are interrogated simultaneously. Since SPR affects only the polarization, the signal due to the polarization can be used as the reference. Consequently, the differential phase between the two polarizations allows us to eliminate all common-path phase noise while keeping the phase change caused by the SPR effect. Experimental results obtained from glycerin–water mixtures indicate that the sensitivity limit of our scheme is refractive-index units per 0.01° phase change. To our knowledge, this is a significant improvement over previously obtained results when gold was used as the sensor surface. Such an improvement in the sensitivity limit should allow SPR biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence. Monitoring of the bovine serum albumin (BSA) binding reaction with BSA antibodies is also demonstrated.
© 2004 Optical Society of America
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