ITO coated optical fiber refractometers based on resonances in the infrared region

In this work, it is presented the fabrication of optical fiber refractometers in the infrared region based on the deposition of indium tin oxide (ITO) coatings onto optical fibers core. ITO coatings act as the resonance supporting layer allowing the coupling of light at specific wavelengths from the waveguide to the ITO-coating/external medium region as a function of the refractive index of the external medium. The utilization of ITO coatings allows the fabrication of robust, highly reproducible and easy to implement resonance based refractometers. The results obtained showed an average sensitivity of 3125 nm/refractive index unit, which is comparable to the existing devices based either on resonance or other techniques. The fabricated devices showed fast response and no dependence with the length of the sensitive region.