Hybrid Fiber-Optic Sensors

With the increasing demand of achieving comprehensive perception in every aspect of life, optical fibers have shown great potential in various applications due to their highly sensitive, highly integrated, flexible and real-time sensing capabilities. Among various sensing mechanisms, plasmonics-based fiber-optic sensors provide remarkable sensitivity benefited from their outstanding plasmon–matter interaction. Therefore, surface plasmon resonance (SPR) and localized SPR (LSPR)-based fiber-optic sensors have captured intensive research efforts. Conventionally, SPR or LSPR-based fiber-optic sensors rely on the resonant electron oscillations of thin metallic films or metallic nanoparticles functionalized on fiber surface. Coupled with the new advances in functional nanomaterials as well as fiber structure design and fabrication in recent years, new solutions continue to emerge to further improve the fiber-optic plasmonic sensors performance in terms of sensitivity, specificity and biocompatibility. For instances, 2D materials like graphene can enhance the surface plasmon intensity at metallic film surface so as the plasmon–matter interaction. 2D morphology of transition metal oxides can be doped with abundant free electrons to facilitate intrinsic plasmonics in visible or near-infrared frequencies, realizing exceptional field confinement and highly sensitivity detection of analyte molecules. Gold nanoparticles capped with macrocyclic supramolecules show excellent selectivity to target biomolecules and ultralow limit of detection. Moreover, specially designed microstructured optical fibers are able to achieve high birefringence that can suppress the output inaccuracy induced by polarization crosstalk meanwhile deliver promising sensitivity. This chapter aims to reveal and explore the frontiers of such hybrid plasmonic fiber-optic platforms in various sensing applications.