Optical fiber refractometers based on indium tin oxide coatings with response in the visible spectral region

This work presents the fabrication of optical fiber refractometers based on indium tin oxide (ITO) coatings with response in the visible spectral region. ITO thin-films have been sputtered by employing a rotating mechanism that enables the fabrication of smooth homogeneous coatings onto the optical fiber core. The ITO coated optical fiber devices present several resonances in the visible and infra-red region. These resonances show high optical power attenuations (more than 10 dB) in the visible spectral region, which produces changes in the colour of the output visible light. Therefore, since these resonances shift as a function of the surrounding medium refractive index (SMRI), it is feasible to determine the refractive index of the outer medium in contact with the ITO coating by simply monitoring the chromatic coordinates of the visible output light.