Irregular hexagonal core based surface plasmon resonance sensor in near-infrared region

Abstract

In this work, a highly sensitive yet simple hexagonal photonic crystal fiber (PCF) based surface plasmon resonance (SPR) refractive index (RI) sensor is proposed. The proposed structure consists of twelve purely circular air-holes to render the fabrication process easily realizable. For the feasibility of operation, the target analyte, and the plasmonic material, Indium Tin Oxide (ITO) are employed around the outer surface of the sensor. The performance of the sensor is numerically analyzed using the full-vectorial finite element method (FEM) for different fiber geometric parameters and RI variations. A step-by-step design procedure has been followed starting from the regular hexagonal lattice PCF structure. The optimal sensor performance is obtained by tuning the geometric parameters over the relevant numeric range. It is shown that the proposed sensor achieves a maximum wavelength sensitivity of 37000 nm/RIU and a maximum amplitude sensitivity of 407.285 RIU-1for a dielectric RI range from 1.33 to 1.40 in the near-infrared wavelength regime (1470 nm − 2220 nm). Apart from this, to ensure high detection accuracy of small refractive index (RI) changes, the sensor achieves the highest wavelength resolution and amplitude resolution of 2.70×10-6 RIU and 2.46×10-5RIU-1, respectively, along with the highest Figure of Merit of 217.65 RIU-1. Hence, the proposed PCF-SPR sensor can potentially be used to detect unknown refractive indices for various applications including biosensing.