Simplicity Meets Sensitivity: A Highly Sensitive Plasmonic Refractive Index Sensor

Plasmonic sensors have brought about a revolutionary change in the field of precision sensing. This study presents the design and numerical investigation of a highly sensitive plasmonic refractive index detector utilizing an easy-to-fabricate photonic crystal fiber (PCF). The sensor comprises only eight air holes arranged symmetrically in a square lattice, both sides of the fiber polished along the vertical axis and externally coated with gold as plasmonic material. The design has been investigated numerically using the finite-element method (FEM). The geometric parameters of the PCF have been optimized for maximizing the amplitude sensitivity (AS). The proposed sensor showcases its ability to detect analytes within a broad sensing range of 1.31–1.42, with a maximum AS of 8267.5 RIU<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^ - 1 $ </tex-math></inline-formula> and a corresponding minimum resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.21\times 10{^ - 6 }$ </tex-math></inline-formula> RIU. Furthermore, the sensor can employ a wavelength interrogation approach with a maximum sensitivity of 12460 nm/RIU and a resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.0257\times 10{^ - 6 }$ </tex-math></inline-formula> RIU, along with a high figure of merit (FOM) of 936.84 RIU<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^ - 1 $ </tex-math></inline-formula>. The simplified design for cost-effective manufacturing, combined with exceptional AS, high FOM, and broad detection range, positions the sensor as an ideal candidate for cost-effective high-precision sensing in various industries, including chemical, medical, and food processing.