D-shaped Micro-structured Optical Fiber Based Surface Plasmon Resonance Sensor with High Sensitivity at Low Refractive Index

A novel D-shaped micro-structured optical fiber (MOF) based surface plasmon resonance (SPR) sensor is designed and numerically investigated, to solve the problem of low sensitivity at the RI range below 1.33 of fiber SPR sensors. By depositing a gold layer on a semicircular ring-shaped channel at the top of the fiber to excite SPR, the RI sensitivity of the sensor can reach 13300 nm/RIU at 1.25, with the resolution of $7.52\times 10^{-6}$ RIU. The RI sensing range can be extended to as low as 1.17 with high sensitivity, which can be used for some low RI analytes detection such as the anesthetic sevoflurane, medical oxygen, and liquid carbon dioxide.