A pH optical fiber sensor based on electromagnetic resonances generated in a waveguide-nanocoating interface is presented here. The incorporation of gold nanoparticles (AuNPs) into polymeric thin films has been deeply studied and the deposition of these thin-films onto an optical fiber core has been performed in order to obtain a resonance-based optical fiber device. The presence of both the metal nanoparticles and the polymers in the coating allows the generation of two different electromagnetic resonances: localized surface plasmon resonance (LSPR) and lossy mode resonance (LMR). These phenomena can be simultaneously observed in the transmitted spectrum. The resultant device has shown a high sensitivity to pH changes from pH 4.0 to pH 6.0, with a large dynamical range and a very fast response.
An optical fiber device showing simultaneously two optical phenomena, localized surface plasmon resonance (LSPR) and lossy mode resonance (LMR), is presented here for the first time. It consists of a fragment of stripped optical fiber coated with a polymeric film that includes gold nanoparticles. The absorption peaks related to both phenomena were captured during the deposition of the coating, showing a different evolution. In addition, the behavior of both phenomena to variations of the surrounding medium refractive index (SMRI) was monitored, studying the different responses of LSPR and LMR.
In this work it is proposed a novel fiber optic humidity sensor based on a functionally coated long-period fiber grating
(LPG). The coating is composed of tetraorthosilicate matrix functionalized with perfluorooctyltriethoxysilane and its
fabrication was performed by the sol-gel technique using a dip coating process using the LPG as substrate. This
technique allows to fabricate sensitive films in a fast and simple way compared to other overlay fabrication techniques.
The fabricated sensor was tested in a programmable temperature and climatic chamber. Relative humidity (RH) was
varied in range from 20%RH to 80%RH at room temperature. The results showed a smooth exponential-like wavelength
shift of the LPG attenuation band.
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