Hollow-core graded index optical fiber refractive index sensor based on surface plasmon resonance

In this paper, a novel topology for refractive index optical fiber sensors based on surface plasmon resonance (SPR) phenomenon is presented. The fiber core has a graded refractive index and there is a hole at the center of the core which is coated by silver. The analyte is injected into the hole. In our structure, there is no need for removing the cladding of the fiber. Two types of graded refractive index profiles are investigated in this paper. The proposed sensor is simulated using finite difference time domain method. The results show that the presented SPR sensor has a good spectral response and suitable sensory specifications. The sensitivity of the proposed sensor is about 4350 nm/RIU. The figure of merit of this sensor is 149 RIU⁻¹. The proposed sensor can be used for measuring refractive indices between 1.38 and 1.49. As a result, it can be used for bio-sensing applications. One of the advantages of the proposed sensor is that it is label-free.