Sensitivity enhancement of phase-sensitive surface plasmon resonance biosensor using multi-pass interferometry

A novel design of multi-pass phase-sensitive surface plasmon resonance (SPR) biosensor is presented. The system is based on differential phase interrogation scheme incorporated to the Michelson or Fabry-Perot interferometer configuration. An intrinsic phase amplification effect is achieved by placing the SPR sensor head in the signal arm of the interferometer so that the interrogating optical beam traverses the sensor surface multiple times. Experimental results obtained from antibody-antigen and protein-DNA binding reaction using both the Michelson and Fabry-Perot interferometer configurations indeed demonstrate the expected phase amplifications factors of 2 and 2.26 respectively in comparison to that obtained by the conventional Mach-Zehnder interferometer configuration. This phase amplification effect leads to the sensitivity enhancement and corresponding resolution improvement by at least 2 times.