Imaging surface plasmon resonance sensor based on multiple wavelengths: Sensitivity considerations

A new, multiple wavelength surface plasmon resonance apparatus for imaging applications is presented. It can be used for biosensing, e.g., for monitor ing of chemical and biological reactions in real time with label-free molec ules. A setup with a fixed incident angle in the Kretschmann configuration with gold as the supporting metal is described, both theoretically and expe rimentally. Simulations of the sensor response based on independently recor ded optical (ellipsometric) data of gold show that the sensitivity for thre e-dimensional recognition layers (bulk) increases with increasing wavelengt h. For two-dimensional recognition layers (adlayer) maximum sensitivity is obtained within a limited wavelength range. In this situation, the rejectio n of bulk disturbances, e.g., emanating from temperature variations, decrea ses, with increasing wavelength. For imaging surface plasmon resonance the spatial resolution decreases with increasing wavelength. Hence, there is al ways a compromise between spatial resolution, bulk disturbance rejection, a nd sensitivity. Most importantly, by simultaneously using multiple waveleng ths, it is possible to maintain a high sensitivity and accuracy over a larg e dynamic range. Furthermore, our simulations show that the sensitivity is independent of the refractive index of the prism. (C) 2000 American Institu te of Physics. [S0034-6748(00)02909-9].