This invention is a platform to improve the functionality of the conventional surface plasmon resonance-based sensors. It consists of a dielectric grating layer with specific dimensions loaded over a plasmonic layer. This platform is designed to be capable of supporting three guiding modes at a fixed wavelength rather than one mode in traditional plasmonifac biosensors. The combination of the three mode spectroscopy enables the sensor to extract more information from the sample under test. Therefore one of the main shortcoming of the plasmonic biosensor which is the cross sensitivity to surface and bulk effects can be solved. Also since this design supports two different polarizations, it can be used to study anisotropic materials. Potential applications include biological sensing, gas detection, breath analysis, pollution monitoring, and security.