A Single Point, Multi-Parameter, Fiber Optic Sensor Based on a Combination of Interferometry and LSPR

We demonstrate a new single point, multi-parameter, fiber optic sensor concept based on a combination of interferometric and plasmonic sensor modalities on an optical fiber end face. The sensor consists of an extrinsic Fabry-Perot interferometer in the form of a hemispherical stimuli-responsive hydrogel with immobilized gold nanoparticles (GNPs). The GNPs exhibit local surface plasmon resonance (LSPR) that is sensitive towards the local refractive index (RI) of the surrounding environment, while the stimuli-responsive hydrogel is sensitive towards specific chemical compounds. We evaluate the quality of the interferometric and LSPR signals as function of GNP concentration and of hydrogel swelling degree stimulated by ethanol solutions. The GNPs have little influence on the visibility of the Fabry-Perot etalon. The swelling degree of the hydrogel, with corresponding bulk RI changes, have little influence on the local surface RI of the GNPs. We expect this novel sensor concept to be of great value for biosensors for medical applications.applications