Refractive index sensor based on SPR in symmetrically etched plastic optical fibers

In this work, we fabricate and characterize a surface plasmon resonance sensor based on etched plastic optical fibers. The etching method used ensures the geometrical circular symmetry of the optical fiber. The sensor was tested by immersion in sensing solutions of different refractive indices and the transmittance is measured using a spectrometer system. The sensor performance in terms of sensitivity and detection accuracy can be controlled by adjusting the design parameters such as gold thickness, residual fiber thickness, and sensing length. We realized a sensitive, cost-effective, and robust sensor suitable for aqueous media sensing by reducing the overall fiber thickness up to 964 μm with a sensing length of 10 mm coated with a thin gold film of around 55 nm. The demonstrated sensor exhibits a sensitivity of 1600 nm/RIU and a full width at half maximum of around 154 nm.