Showing papers by "Ignacio Del Villar published in 2006"
TL;DR: In this article, the effect of a thin overlay of higher refractive index than that of the cladding of a long-period fiber grating on the transmission spectrum was studied.
Abstract: A thin overlay of higher refractive index than that of the cladding of a long-period fiber grating induces in cladding modes strong variations in effective index, mode profile, cross-coupling coefficient with the core mode, and self-coupling coefficient. Some conditions must be met in order to obtain the highest inducement. The key parameters are the thickness and the refractive index of the overlay, and the ambient refractive index. Under optimum conditions, the sensitivity of the device to variations in any of the critical parameters is improved in a great manner. The result is large shifts of the attenuation bands in the transmission spectrum. If the refractive index of the overlay is complex, there is an additional phenomenon of vanishing of the attenuation bands in the transmission spectrum. This occurs for specific thickness values of the overlay. The problem is solved in two steps: a vectorial analysis of the modes and the application of coupled-mode theory.
56 citations
TL;DR: The incremental deposition of a thin overlay on the cladding of a long-period fiber grating induces important resonance wavelength shifts in the transmission spectrum with the particularity that the shape of the resonance wavelength shift depends on the thickness of the overlay.
Abstract: The incremental deposition of a thin overlay on the cladding of a long-period fiber grating (LPFG) induces important resonance wavelength shifts in the transmission spectrum. The phenomenon is proved theoretically with a vectorial method based on hybrid modes and coupled mode theory, and experimentally with electrostatic self-assembly monolayer process. The phenomenon is repeated periodically for specific overlay thickness values with the particularity that the shape of the resonance wavelength shift depends on the thickness of the overlay. The main applications are the design of wide optical filters and multiparameter sensing devices.
24 citations
TL;DR: A fiber-optic biosensor for glucose concentration detection has been designed, based on electrostatic self-assembly as discussed by the authors, where the end face of a multimode fiber is coated with poly(allylamine hydrochloride) in combination with Prussian blue and the enzyme glucose oxidase.
Abstract: A fiber-optic biosensor for glucose concentration detection has been designed, based on electrostatic self-assembly. The end face of a multimode fiber is coated with poly(allylamine hydrochloride) in combination with Prussian blue and the enzyme glucose oxidase. The glucose concentration that can be measured ranges between 0.06 and 2 mM. The initial velocity of change of the output biosensor signal has been found to be linear in the glucose concentration. The sensor recovers after immersion in ascorbic acid. The pH values analyzed range between 5 and 7. The sensitivity of the device has been increased by adjusting the number of bilayers and by adding some capping bilayers at the end of the structure.
20 citations