Surface plasmon resonance (SPR) and common-path phase-shift interferometry (PSI) techniques are integrated in a biosensing imaging system for measuring the two-dimensional spatial phase variation caused by biomolecular interactions on a sensing chip without the need for additional labeling. The common-path PSI technique has the advantage of long-term stability, even when it is subjected to external disturbances. Hence the system meets the requirements of the real-time kinetic studies involved in biomolecular interaction analysis. The proposed SPR-PSI imaging system demonstrates a detection limit of a 2×10^-7 refractive-index change, a long-term phase stability of 2.5×10^-4 pi rms for 4 h, and a spatial phase resolution of 10^-3 pi with a lateral resolution of 100 µm.
© 2005 Optical Society of America
Y.-D. Su, S.-J. Chen, and T.-L. Yeh, "Common-path phase-shift interferometry surface plasmon resonance imaging system," Opt. Lett. 30, 1488-1490 (2005)