Multimode spectroscopy using dielectric grating coupled to a surface plasmon resonance sensor.

A new platform is proposed to solve one of the main shortcomings of surface plasmon resonance biosensors, namely, the cross sensitivity to surface and bulk effects. This approach is based on multimode spectroscopy in which three different modes are excited simultaneously. The proposed design consists of an SPR sensor loaded with a dielectric grating. The design parameters (dimensions and wavelength) are optimized with a genetic algorithm. The optimized design has two resonance modes excited with TM polarized light, each sensitive to surface effects, and one TE mode mostly sensitive to variations in the bulk fluid refractive index. Numerical and analytical methods are used to justify the simulation results, which are in good agreement. Finally, it is shown that, by applying three-mode spectroscopy, decoupling the properties of the attached biomaterial from the background index variations is possible with the proposed design.