Experimental study and sensing applications of polarization-dependent lossy mode resonances generated by D-shape coated optical fibers

The fabrication and characterization of an optical fiber refractometer based on lossy mode resonances (LMR) is presented. TiO₂/poly (sodium 4-styrenesulfonate) (PSS) coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. LMRs are sensitive to the external medium refractive index, and D-shaped optical fibers enable the observation of TE and TM LMR polarizations. These refractometers based on TE and TM LMR showed an average sensitivity of 2737 nm/RIU and 2893 nm/RIU, respectively, for a surrounding medium refractive index range from 1.35 to 1.41. This study also explores the utilization of previously described refractometers in the context of two common industrial applications, such as the determination of the sugar content or °Brix in beverages and the salt concentration in sea water.