Refractive index sensitivity of optical fiber lossy-mode resonance sensors based on atomic layer deposited TiOx thin overlay

This work presents an optical fiber refractive index sensors based on lossy–mode resonance (LMR) effect supported by titanium oxide (TiOx) thin overlay. The TiOx overlays of different thickness were deposited on core of polymer-clad silica (PCS) fibers using atomic layer deposition (ALD) method. Based on numerical simulations, a number of structures differing in the location of exposed core area and the thickness of TiOx coatings were designed. For fabricated structures the spectral response to external refractive index (next) was measured. The maximum sensitivity reaches 634.2 nm/RIU (next range: 1.357 - 1.402 RIU; TiOx coating thickness: 260.9 nm; investigated spectral range: 500-800 nm) and it highly depends on the thin-film thickness.

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