Optical fiber refractometers based on Lossy Mode Resonances by means of SnO₂ sputtered coatings

The fabrication of optical fiber refractometers by means of the deposition of a thin tin-dioxide coating onto an optical fiber core is presented. Tin-dioxide permits the guided light in the fiber to be coupled from its core to its coating, creating lossy mode resonances in the infrared and visible regions. These resonances vary as a function of the external medium's refractive index, enabling the fabrication of robust and highly reproducible wavelength-based optical fiber refractometers. Moreover, the first seven lossy modes create seven differentiated resonances which have been studied in the range between 450 and 1650 nm of the optical spectrum. The central wavelength of the resonances can be adjusted by varying the thickness of the tin-dioxide coating.