Resonance-based refractometric response of cladding-removed optical fibers with sputtered indium tin oxide coatings

Here it is presented the fabrication of thin and homogeneous indium tin oxide (ITO) coatings onto cladding-removed optical fibers by means of the sputtering technique. ITO coatings permit to couple light at specific resonance from the optical fiber core to the coating. Fabricated devices show a resonance shift in the visible and near infrared region when the refractive index of the surrounding medium in contact with the coating is varied, which makes possible its utilization as a refractometer. It has been also demonstrated that a post-processing of the sputtered ITO coatings by means of a thermal annealing enables to shift the resonances. Furthermore, the high attenuation of the resonances in the visible spectral range facilitates the observation of a change in the output light color, which could be useful for the fabrication of optical filters or even the determination of refractive index by means of color detection.