Mode transitions and thickness measurements during deposition of nanoscale TiO2 coatings on tilted fiber Bragg gratings

Date

2022

Director

Publisher

IEEE
Acceso abierto / Sarbide irekia
Artículo / Artikulua
Versión aceptada / Onetsi den bertsioa

Project identifier

  • AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-106231RB-I00/ES/ recolecta
Impacto
No disponible en Scopus

Abstract

The mode transition is a phenomenon observed in thin film coated long period fiber gratings (LPGs) and singlemode multimode single-mode (SMS) fibers for certain values of the coating thickness and refractive index, resulting in increased sensitivity for sensing applications. It is shown here that mode transitions occur simultaneously for a large number of mode resonances in the transmission spectra of tilted fiber Bragg gratings (TFBG) measured during the deposition of ~350nm thick TiO2 coatings by Atomic Layer Deposition (ALD). In TFBGs, the mode transition shows up as an acceleration of the resonance wavelength shift vs thickness, but without fading of the resonance amplitude. Furthermore, the results show that the mode transition for cladding modes with predominantly “TE” polarization at the cladding boundary is significantly sharper than that of predominantly “TM” polarized modes and that it occurs at a smaller coating thickness (<100 nm vs >200 nm). Finally, using a separately determined coating refractive index (2.14, by ellipsometry on witness flats deposited simultaneously) and simulations of the resonance shifts of the TFBG with coating thickness, it is demonstrated that a TFBG connected to a spectral interrogation system can be used to measure the growth of a coating on the surface of the fiber in real time.

Description

Keywords

Fiber optic sensors, Mode transition, Thin films, Tilted fiber Bragg gratings

Department

Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren / Institute of Smart Cities - ISC / Ingeniería Eléctrica, Electrónica y de Comunicación

Faculty/School

Degree

Doctorate program

item.page.cita

J. J. Imas, J. Albert, I. D. Villar, A. Ozcáriz, C. R. Zamarreño and I. R. Matías, "Mode Transitions and Thickness Measurements During Deposition of Nanoscale TiO2 Coatings on Tilted Fiber Bragg Gratings," in Journal of Lightwave Technology, vol. 40, no. 17, pp. 6006-6012, 1 Sept.1, 2022, doi: 10.1109/JLT.2022.3186596

item.page.rights

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