title: Low-Coherence Interferometric Fiber-Optic Sensors with Potential Applications as Biosensors.
abstract: Fiber-optic Fabry-Pérot interferometers (FPI) can be applied as optical sensors, and excellent measurement sensitivity can be obtained by fine-tuning the interferometer design. In this work, we evaluate the ability of selected dielectric thin films to optimize the reflectivity of the Fabry-Pérot cavity. The spectral reflectance and transmittance of dielectric films made of titanium dioxide (TiO₂) and aluminum oxide (Al₂O₃) with thicknesses from 30 to 220 nm have been evaluated numerically and compared. TiO₂ films were found to be the most promising candidates for the tuning of FPI reflectivity. In order to verify and illustrate the results of modelling, TiO₂ films with the thickness of 80 nm have been deposited on the tip of a single-mode optical fiber by atomic layer deposition (ALD). The thickness, the structure, and the chemical properties of the films have been determined. The ability of the selected TiO₂ films to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments, and to create multi-cavity interferometric sensors in FPI has then been studied. The presented sensor exhibits an ability to measure refractive index in the range close to that of silica glass fiber, where sensors without reflective films do not work, as was demonstrated by the measurement of the refractive index of benzene. This opens up the prospects of applying the investigated sensor in biosensing, which we confirmed by measuring the refractive index of hemoglobin and glucose.
authors.affiliation: Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza Street 11/12, 80-233 Gdańsk, Poland. matthieu.weber@umontpellier.fr.
authors.forename: Marzena
authors.initials: M
authors.lastname: Hirsch
authors.affiliation: Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza Street 11/12, 80-233 Gdańsk, Poland. mikhael.bechelany@univ-montp2.fr.
authors.forename: Daria
authors.initials: D
authors.lastname: Majchrowicz
authors.affiliation: Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza Street 11/12, 80-233 Gdańsk, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Wierzba
authors.affiliation: Institut Européen des Membranes, UMR-5635, Université de Montpellier, École Nationale Supérieure de Chimie de Montpellier, Centre national de la recherche scientifique, Place Eugène Bataillon, Montpellier 34095, France. matthieu.weber@umontpellier.fr.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Weber
authors.affiliation: Institut Européen des Membranes, UMR-5635, Université de Montpellier, École Nationale Supérieure de Chimie de Montpellier, Centre national de la recherche scientifique, Place Eugène Bataillon, Montpellier 34095, France. mikhael.bechelany@univ-montp2.fr.
authors.forename: Mikhael
authors.initials: M
authors.lastname: Bechelany
authors.affiliation: Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza Street 11/12, 80-233 Gdańsk, Poland. mjedrzej@eti.pg.gda.pl.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Jędrzejewska-Szczerska
keywords: Fabry-Pérot interferometers; atomic layer deposition; fiber-optic sensor; interference; titanium dioxide thin film