Advanced biosensing using simultaneous excitation of short and long range surface plasmons

We present a novel optical biosensor which exploits simultaneous excitation of two different surface plasmons in a single sensing spot. It allows compensation of cross-sensitivity to background refractive index change, as a typical surface plasmon resonance sensor is sensitive to both the absorption of a thin film on the surface (sensing event) and the refractive index change of the background (an interfering effect). The structure parameters are optimized to yield low noise and minimum cross-sensitivity. In the performed model experiment, IgE biomolecules at a concentration of 250 ng ml−1 are detected during a change in the background refractive index of 10−3.