Optical heterodyne surface-plasmon resonance biosensor.

A novel optical heterodyne surface-plasmon resonance (SPR) biosensor with a Zeeman laser is proposed. Two surface plasma waves are excited by two correlated p-polarized waves in a SPR device of the Kretschmann configuration. Two reflected p waves are optically heterodyned such that the magnitude of the heterodyned signal is proportional to the multiplication of two attenuated reflected p waves. Then the detection sensitivity and the dynamic range based on this amplitude-sensitive method are enhanced. In the experiment, the kinetics between mouse immunoglobulin G (IgG) and rabbit antimouse IgG is obtained from sensograms of various concentrations of antimouse IgG. A detection sensitivity of 0.2 nM was achieved. In addition, a concentration of 5 ng/ml of protein G interacting with mouse IgG was measured successfully.