High sensitivity for toxic metal ion sensor based on tapered PCF Mach-Zehnder interferometer

In this study, two regular single-mode fibers [SMF] and two regular multimode fibers [MMF] are combined with a photonic crystal fiber [PCF] [SMF-PCF-SMF] and a photonic crystal fiber MMF-PCF-MMF, respectively, to create a surface plasmon resonance (SPR) based on a Mach-Zehnder interferometer MZI for measuring the refractive index RI for the ion toxic metal nickel using a sensing tapered PCF. The PCF side can be tapered to create the SPR curve, which is then obtained by coating a gold (Au) film over the tapered region. Results of the studies show a clear SPR effect for the suggested sensor, and it was estimated and calculated signal-to-noise ratio (SNR), resolution (R), figures of merit (FOM), and sensitivity (S) are advancing; the SNR 0.18, S is 11.11 mu m/RIU, resolution 1.7 x 10(-4), and the FOM 22.87 for single-mode fiber-photonic crystal fiber-single-mode fiber [SMF-PCF-SMF], while performance metrics for multimode fiber-photonic crystal fiber-multimode fiber [MMF-PCF-MMF]; for example, the (S) is nearing 10 mu m/RIU, FOM is 90.9, resolution is 1 x 10(-4), and SNR is 0.209 are achieved.