First step towards an interferometric and localized surface plasmon fiber optic sensor

We present a first demonstration of a novel multi-parameter fiber optic (FO) sensor concept based on gold nanoparticles (GNP) embedded in a stimuli-responsive hydrogel material. A hemispherical hydrogel immobilized on the optical fiber end-face forms a low-finesse Fabry-Perot (FP) interferometer. The GNPs exhibit local surface plasmon resonance (LSPR) that is sensitive towards the refractive index of the surrounding environment, while the stimuli-responsive hydrogel is sensitive towards specific chemical compounds. We evaluate the quality of the interferometric and LSPR signal as a function GNP concentration and of hydrogel swelling degree stimulated by ethanol solutions. The GNPs shows to have little influence on the visibility of the FP etalon, while LSPR of GNP shows to be sensitive towards the surface refractive index rather than bulk refractive index. This demonstration shows that the sensor concept has the potential to be used in applications such as an intravenous two-parametric real-time sensor for medical purpose.