Study of a Surface Plasmon Resonance-Based Optical Fiber Sensor for Nitrate Detection

Mohammed Hussein Ibrahim; Rasoul Aalipour Kosalar

doi:10.51699/cajmns.v7i2.3111

Authors

Mohammed Hussein Ibrahim Department of Physics, College of Education for pure Science, University of Azarbaijan Shahid Madani
Rasoul Aalipour Kosalar Department of Physics, College of Education for pure Science, University of Azarbaijan Shahid Madani

DOI:

https://doi.org/10.51699/cajmns.v7i2.3111

Keywords:

Photonic Crystal Fiber, Surface Plasmon Resonance, Nitrate, Optical Sensitivity

Abstract

This article presents the design, simulation, and analysis of a surface plasmon resonance (SPR) sensor based on solid twin-core photonic crystal fibers (PCFs) for detecting nitrate concentration in aqueous solutions. The motivation stems from the urgent need for sensitive, compact, real-time monitoring systems capable of addressing the growing challenges of water pollution and environmental management. The sensor structure was designed and simulated using COMSOL Multiphysics, with gold as the plasmonic layer and aqueous nitrate solutions as the analyte. The study investigated the variation of the effective refractive index and confinement loss with wavelength in the range of 800–1800 nm, complemented by two-dimensional field distributions to visualize plasmon coupling at the fiber-metal-analyte interface. The results showed that the resonance wavelength shifts to red in a consistent manner with increasing nitrate concentration, confirming the strong dependence of the plasmonic phase matching on the refractive index of the material to be analyzed. The sensitivity of the sensor was evaluated from the slope of the linear fit of the Re(n_eff) data versus wavelength, expressed in RIU/nm, and the derived values showed an approximately linear increase across the studied concentration range, confirming the validity of the proposed scale. Overall, the results confirm that the proposed dual-core PCF–SPR sensor offers high sensitivity, predictable performance, and practical potential for monitoring nitrates in water, providing a basis for future experimental investigation and application in the field of environmental sensing.

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