Extremely high sensitive plasmonic refractive index sensors based on metallic grating

This work shows that a grating-based surface plasmon (SP) resonance sensing system can exhibit extremely high sensitivity to detect a small change of refractive index in an analyte. The corresponding sensitivity can be much higher than that of the prism-based systems. Both analytical calculation and rigorous coupled-wave analysis are used to study the angular sensitivity of the system. It is found that the system's sensitivity can be over 600° per unit index change if (1) first-order diffracted wave is chosen to excite SP mode, (2) large SP resonant angles are used in the operation, and (3) grating filling factor is selected to be varied between 0.3 and 0.7. Furthermore, the sensing system has the best performance for detecting low-index analyte with a small change of refractive index.