A surface plasmon resonance sensor system including a high refractive index prism, a sensor chip, a light source having multiple wavelengths over a broad range of wavelengths, optical lenses, a photodetector, a data acquisition unit, and as defined herein. The sensor chip can include, for example, a thin layer of silicon and gold on one face of a transparent substrate and the prism adjacent to the opposite face of the transparent substrate. Such an arrangement provides variable penetration depths up to about 1.5 micrometers with a dynamic range for sensing index of refraction changes in a sample that are several times greater than that of a conventional SPR sensor. The disclosure provides methods for using the surface plasmon resonance sensor system for cell assay or chemical assay related applications.