Generation of lossy mode resonances by deposition of high-refractive-index coatings on uncladded multimode optical fibers

A comparative study of lossy mode resonances generated by depositing two different materials is presented. The two materials selected are indium tin oxide (ITO) and indium oxide. The two materials present different dielectric dispersion, which leads to the generation of single-peak lossy mode resonances with the ITO coated optical fibers and dual-peak lossy mode resonances with the In₂O₃ coated optical fibers. The obvious advantage of a dual-peak based measurement in the sensors field is enhanced by a sensitivity increase observed in sensors based on In₂O₃ if compared with those based on ITO. These characteristics are analyzed both theoretically and experimentally.