Surface plasmon resonance biosensor incorporated in a Michelson interferometer with enhanced sensitivity

A novel double-pass phase-sensitive surface plasmon resonance (SPR) biosensor based on a Michelson interferometer with differential phase interrogation is presented. The new setup provides an intrinsic resolution enhancement of up to two times in terms of achievable detection sensitivity due to an amplification effect in the SPR phase change when we place the SPR sensor head in the signal arm of the interferometer so that the interrogating optical beam traverses the sensor surface twice. Experimental results obtained from saltwater mixtures and antibody-antigen binding reactions confirmed the expected sensitivity enhancement as compared to the conventional SPIR biosensor based on a Mach-Zehnder interferometer.