Dual-mode independent detection of pressure and refractive index by miniature grating-coupled surface plasmon sensor.

Multiple parameters need to be monitored to analyze the kinetics of biological progresses. Surface plasmon polariton resonance sensors offer a non-invasive approach to continuously detect the local change of refractive index of molecules with high sensitivity. However, the fabrication of miniaturized, compact, and low-cost sensors is still challenging. In this paper, we propose and demonstrate a grating-coupled SPR sensor platform featuring dual mode operation for simultaneous sensing of pressure and refractive index, which can be fabricated using a highly-efficient low-cost method, allowing large-scale production. Both sensing functionalities are realized by optical means via monitoring the spectral positions of a surface plasmon polariton mode (for refractive index sensing) and Fabry-Perot or metal-insulator-metal modes (for pressure sensing), which are supported by the structure. Simultaneous measurement of refractive index with the sensitivity of 494 nm/RIU and pressure was demonstrated experimentally. The proposed platform is promising for biomonitoring that requires both high refractive index sensitivity and local pressure detection.