(IEEE, 2023) López Torres, Diego; Elosúa Aguado, César; Pappas, Georgios A.; Konstantaki, Maria; Klini, Argyro; Lappas, Alexandros; Arregui San Martín, Francisco Javier; Pissadakis, Stavros; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a zinc oxide (ZnO) out-cladding,
overlaid optical fiber Bragg grating sensor, for the detection
of vapors of common alcohols and acetone at concentrations
lower than 25 ppm while operating at room temperature (RT).
The optical fiber sensing results indicate a chemostriction
effect occurring in the ZnO layer when exposed to volatile
organic compounds (VOCs), which in turn induces shifts in
the cladding, and most importantly, in the core confined,
Bragg mode. The sensor exhibits a maximum sensitivity
of ∼1 pm/ppm to ethanol vapors, with exposure to other
alcohol vapors (isopropanol and methanol) showing lower
sensitivities; also, response to acetone vapors was traced at
∼0.5 pm/ppm. X-ray diffraction (XRD) measurements of the
ZnO nanolayer revealed that, in saturated ethanol vapors atmosphere, the polycrystalline ZnO film undergoes a contraction by 0.6% of the interplanar distance corresponding to the (002) crystalline direction, denoting the chemostrictive
effect through an underlying piezotronic mechanism. XRD measurements and optical fiber sensing data are further
correlated by numerical simulations carried out, so to study the strain interactions of the ZnO layer with the silica glass
optical fiber.
