Polarization-independent tilted fiber Bragg grating surface plasmon resonance sensor based on spectrum optimization

We experimentally demonstrated polarization multiplex-ing schemes in a tilted fiber grating (TFBG) to achieve polarization-independent fiber-optic surface plasmon reso-nance (SPR) sensors. The first used two orthogonal polarized lights separated by a polarization beam splitter (PBS) that are p-polarized in polarization-maintaining fiber (PMF) and precisely aligned with the tilted grating plane, so as to achieve the transmission of p-polarized light in two opposite direc-tions of the Au-coated TFBG to excite SPR. Alternatively, polarization multiplexing was also achieved by exploring two polarization components to achieve the SPR effect through a Faraday rotator mirror (FRM). The SPR reflection spec-tra are polarization-independent of the light source and any perturbations to fibers, which are explained by the superposition of p-and s-polarized transmission spectra in equal proportions. The spectrum optimization is presented to reduce the proportion of the s-polarization component. A polarization-independent TFBG-based SPR refractive index (RI) sensor with a wavelength sensitivity of 555.14 nm/RIU and an amplitude sensitivity of 1724.92 dB/RIU for small changes is obtained, exhibiting unique advantages of mini-mizing the polarization alterations by mechanical perturba-tions. & COPY; 2023 Optica Publishing Group

Automated summary

This article experimentally demonstrates polarization multiplexing schemes in a tilted fiber grating (TFBG) for achieving polarization-independent fiber-optic surface plasmon resonance (SPR) sensors. Two orthogonal polarized lights separated by a polarization beam splitter (PBS) were used to excite SPR in the Au-coated TFBG in two opposite directions, while another method involved using a Faraday rotator mirror (FRM) to achieve polarization multiplexing for SPR effect. The resulting SPR reflection spectra were independent of the light source and fiber perturbations due to the superposition of p- and s-polarized transmission spectra. A polarization-independent TFBG-based SPR refractive index (RI) sensor with high sensitivity was obtained.