Patent ID: 8163561

Claim:
A method for depth resolved sensing of a biological entity, comprising: providing a surface plasmon resonance (SPR) sensor system comprising: at least one light source providing at least one incident beam, the beam having at least two wavelengths; first optics providing incident beam shaping and beam focusing; a sensor chip comprising a transparent substrate having on the first face of the substrate a high refractive index prism for receiving the incident focused beam, and having on the second face of the substrate a silicon layer of from about 100 nm to about 5 micrometers, a precious metal layer of from about 30 nm to about 80 nm on the silicon layer; second optics providing reflected or emitted beam collection; a photodetector for receiving the collected beam and detecting the SPR signal; a data acquisition unit; and a biological entity on the precious metal outer surface layer of the sensor chip surface; irradiating the sensor with the at least two different wavelengths, each of the different wavelengths providing a different penetration depth; monitoring each of the different wavelengths for a change in the index of refraction; and correlating the change in the index of refraction to a change in the biological entity.