Cladding etched single mode optical fiber refractometer based on Lossy Mode Resonances

Fabrication and characterization of an optical fiber refractometer based on Lossy Mode Resonances is presented. Tin oxide (SnO₂) coatings deposited on cladding etched single mode optical fibers are used as LMR supporting coatings, which are sensitive to the external medium refractive index. These refractometers showed an average sensitivity of 3680 nm/RIU with a dynamic range of 196 nm, for a surrounding medium refractive index range of 1.3339 to 1.3865. Chemical etching of the single mode optical fiber provides a simple method to get access to the evanescent field of light, without affecting the core of the optical fiber and with highly repeatable results on the final dimensions. LMRs have been proved, for the first time, to be a good phenomenon to make this structure sensitive to the surrounding medium refractive index.