Ultra-Wide Refractive Index Range Photonic Crystal Fiber Based Sensor with Gallium Doped Zinc Oxide Coating

A refractive index (RI) sensor with an ultrawide detection range (1.24-1.40) based on photonic crystal fiber (PCF) utilizing surface plasmon resonance (SPR) is proposed and analyzed which works in the near-infrared (NIR) wavelength region (1160-1840 nm). The sensor structure consists of 20 air-holes with a square-shaped core that renders easy fabrication. The full-vectorial-based finite element method (FEM) is used to build and investigate the impact of various geometric values on the sensor’s sensing characteristics. To the best of our knowledge, this is the first-ever PCF-SPR sensor based on Gallium doped Zinc Oxide (GZO). The designed sensor attains enhanced wavelength sensitivity (WS) of 17000 nm/RIU (Refractive Index Unit) and amplitude sensitivity (AS) of -135.817RI$\mathrm{U}^{-1}$. Besides, the sensor exhibits higher detection accuracy such as wavelength resolution of $5.88\times 10^{-6}\mathrm{R}\mathrm{I}\mathrm{U}^{-1}$ and amplitude (ampl) resolution of 7. $36\times 10^{-6}\mathrm{R}\mathrm{I}\mathrm{U}$. Due to ultra-wide detection range, higher sensitivity, use of alternative plasmonic material (GZO), lower material cost, outer annular detection channel proposed sensor is suitable to identify unknown RI of various samples in sensing applications.