A high sensitivity D-type surface plasmon resonance optical fiber refractive index sensor with graphene coated silver nano-columns

Abstract

A high sensitivity surface plasmon resonance (SPR) fiber sensor with graphene coated silver nano-columns on the surface of the D-type single mode fiber has been proposed and simulated in this paper. The sensor uses evanescent wave on the surface of the fiber to excite free electrons on the metal surface to generate surface plasmon waves (SPW), and the change of refractive index (RI) is measured by monitoring the variation of the resonance absorption peak. The COMSOL Multiphysics software is used to optimize the diameter of sliver nano-column, the width of air gap between sliver columns, and to study the effect of graphene sensing layer thickness on sensor sensitivity. The simulation results show that the sensitivity of the sensor can be greatly improved with graphene coated sliver nano-columns. The maximum external RI response sensitivity of the sensor proposed in this paper can reach 8860.93 nm/RIU in the RI range of 1.33–1.39 when the diameter of silver nano-column is 90 nm, the graphene is 23 layers and the width of air gap between columns is 53.82 nm. When the RI is 1.39, the sensitivity of the sensor with 23 layers of graphene can be increased by 28% compared with the sensor without the graphene layer. The simulation results will be helpful for design and fabrication of optical fiber SPR refractive index sensor.