Tilted fiber Bragg grating surface plasmon resonance based optical fiber cadmium ion trace detection

A plasmonic tilted fiber Bragg grating (TFBG)-based sensor for the detection of cadmium ion (Cd2+) is proposed and demonstrated experimentally. The TFBG is coated with a thin gold film, where glutathione (GSH) can self-assemble on the gold coating to bond Cd2+ and form complexes. To enhance Cd2+ sensitivity, GSH-modified gold nanoparticles are used to amplify localized refractive index changes around TFBG surface, induced by Cd2+ concentration variations. The experimental results indicate a limit of detection of ∼0.06 nM, which is two orders better than reported fiber grating-based Cd2+ sensors. Additionally, the proposed TFBG sensor performs a wide dynamic range from 0.01 nM to 1000 nM for Cd2+ detections and temperature-compensated wavelength monitoring with Bragg resonance.