Demodulation technique for plasmonic fiber grating sensors using orthogonally polarized light states

摘要

The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs) strongly depends on the state of polarization of the core guided-light. Recently, it was demonstrated that rotating the linear state of polarization of the guided light by 90° with respect to the grating planes allows to turn the SPR on and off. In this paper, we demonstrate that this strong polarization dependence can be advantageously used to demodulate the TFBG amplitude spectrum and retrieve the SPR shift induced by a change of the surrounding refractive index. The correlation between two amplitude spectra recorded with two particular orthogonally polarized light states yields a new refractive index measurement method accurate to ~2 10~(-5).