Multicore Photonic Crystal Fiber Plasmonic Sensor

In this work, due to the importance of photonic crystal fibers (PCFs) in sensing and biosensing applications, three plasmonic PCF structures are investigated as refractive index sensors. The PCF cores are provided near the interface with the surrounding medium so that by adding a noble metal layer on the PCF, the evanescent field of the cores can excite the surface plasmons of the metal. The plasmonic PCFs are immersed in different analytes with different refractive indices to detect the variation of analyte refractive index. These three structures are investigated to determine the effect of the number of cores on the sensing properties of the plasmonic PCF. By various calculations and also simulation with finite element method (FEM), the best characteristics of the PCFs are obtained. We have found that the optimum structure is the double-core PCF plasmonic sensor with sensitivity of 2333.33 nm per refractive index unit (nm/RIU), figure of merit (FOM) of $110 \mathrm{RIU}^{-1}$, and sensor resolution of 0.00214. This sensor has a linear response with 99.7% accuracy to detect the refractive index of biological materials. Therefore, such a sensor can be useful in biomedical diagnosis and environmental monitoring applications.