Radiation tolerant humidity sensors based on nano-scale TiO2-coated LPGs for high-energy physics applications

This contribution deals with a feasibility analysis for the development of radiation tolerant fiber optic humidity sensors based on long period grating (LPG) technology to be applied in high-energy physics (HEP) experiments currently running at the European Organization for Nuclear Research (CERN). Here we propose a high-sensitivity LPG sensor coated with a finely tuned titanium dioxide (TiO₂) thin layer (~100 nm thick) for relative humidity (RH) monitoring in the humidity range [0-75]%RH and in the temperature range [-10°C, 25]°C. Experimental results demonstrate the very high RH sensitivities of the proposed device (up to 1.4 nm/%RH at low humidity). The TiO₂-coated LPG sensor radiation tolerance is also investigated up to 1Mrad γ-ionizing radiation dose. Collected results demonstrate the strong potentialities of the proposed technology in light of its future exploitation in HEP applications.