title: Fiber-optic pH-sensors in long-period fiber gratings using electrostatic self-assembly.
abstract: A novel pH sensor based on the deposition of electrostatic self-assembled polyallylamine hydrochloride and polyacrylic acid on the cladding of a long-period fiber grating has been designed. The overlay thickness is of the order of magnitude of the light wavelength used to interrogate the sensor. A theoretical model of multilayer cylindrical waveguides based on coupled-mode theory has been used to predict the position of the attenuation bands as a function of the overlay thickness. A study of the role that pH plays in the thickness of the sensitive overlay was carried out. Experimentally, a wavelength shift of the attenuation bands of up to 85 nm was obtained in the 4-7 range of pH units. The results are reproducible, which indicates the possibilities of a multiple-use sensor.
authors.affiliation: Departmento de Ingenieria Electrica y Electronica, Universidad Publica de Navarra, Campus Arrosadia, Pamplona, Navarra, Spain. jmcorres@unavarra.es
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Corres
authors.forename: Ignacio
authors.initials: I
authors.lastname: del Villar
authors.forename: Ignacio R
authors.initials: IR
authors.lastname: Matias
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Arregui