Abstract
We have established a high resolution and real-time detection surface plasmon resonance biosensor based on common-path heterodyne interferometry. It could achieve very high sensitivity by adjusting the fast axis of a quarter waveplate (QWP), and have better signal-to-noise ratio by using a lock-in amplifier. The system with QWP can measure the concentration down to three orders than that without quarter waveplates. The measurenent targets are biospecific antibody and antigen of sheep. Our setup could measure low concntration as low as 55ng/ml of anti-sheep IgG without QWP, which is better than that of Biacore X system by Biacore Inc.. We could measure concentration as low as 11ng/ml after added two QWPs in our setup. The system is estimated to have the resolution as low as .