Optimization of sensitivity in Long Period Fiber Gratings with overlay deposition

Universidad de Navarra, Iruña, Navarre, Spain
Optics Express (Impact Factor: 3.53). 02/2005; 13(1):56-69. DOI: 10.1364/OPEX.13.000056
Source: PubMed

ABSTRACT The deposition of an overlay of higher refractive index than the cladding in a Long Period Fiber Grating (LPFG) permits to improve the sensitivity to ambient refractive index changes in a great manner. When the overlay is thick enough, one of the cladding modes is guided by the overlay. This causes important shifts in the effective index values of the cladding modes, and henceforward fast shifts of the resonance wavelength of the attenuations bands in the transmission spectrum. This could be applied for improving the sensitivity of LPFG sensors. The problem is analysed with a numerical method based on LP mode approximation and coupled mode theory, which agrees with so far published experimental results.

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Available from: Ignacio Del Villar, Feb 07, 2014
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    • "Recently, the combination of this phenomenon with the dispersion turning point [8] has permitted achieving sensitivities approaching 10000 nm/RIU [9]. The mode transition consists of a reorganization of the effective indices of cladding modes when one of these modes is guided through the thin-film deposited on the cladding of an LPFG [5]. Recently, new simpler structures that do not require the inscription of a grating have been explored when a thin-film is deposited on the cladding. "
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    ABSTRACT: Two simple optical fibre structures that do not require the inscription of a grating, a cladding removed multimode optical fibre (CRMOF) and a single-mode multimode single-mode structure (SMS), are compared in terms of their adequateness for sensing once they are coated with thin-films. The thin-film deposited (TiO2/PSS) permits increasing the sensitivity to surrounding medium refractive index. The results obtained can be extrapolated to other fields such as biological or chemical sensing just by replacing the thin-film by a specific material.
    Journal of Sensors 06/2015; 2015(Article ID 763762). DOI:10.1155/2015/763762
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    • "The underlying idea of the SMS-based devices is basically the modulation of the effective index of cladding modes, which permits to tune the position of the transmission/attenuation bands produced by a coupling of light from a mode guided in the core to modes guided in the cladding [18]. Following the same principle, the effective index of the modes guided in the MMF section of the SMS structure should also be modified by using a thin-film. "
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    ABSTRACT: Multimode interference in a single-mode–multimode–single-mode (SMS) fibre structure leads to thegeneration of transmission bands and attenuation bands in the optical spectrum. In this work, the pro-gressive deposition, with layer-by-layer assembly technique, of a high refractive index thin-film onto theSMS structure permits to observe the evolution of the bands as a function of the coating thickness. Theresults show that it is possible to increase the sensitivity of the device to variations of the coating thick-ness, what indicates the adequateness of this structure as a sensing platform. The experimental resultsare corroborated with a numerical method based on coupled-mode theory. As a practical application, asensitivity improvement has been obtained a pH sensor by increasing the coating thickness.
    Sensors and Actuators B Chemical 01/2014; 190:363. DOI:10.1016/j.snb.2013.08.090 · 4.29 Impact Factor
    • "The resonances for indium–oxide occur for a lower thickness than for ITO [11]. Moreover, the propagation constant of the guided mode varies more abruptly as a function of three key parameters: the coating RI, the coating thickness and the surrounding medium's RI [17]. Hence, indium–oxide coatings cause a greater resonance wavelength shift and so a better sensitivity is obtained. "
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    ABSTRACT: The fabrication of optical fiber refractometers by means of the deposition of a thin indium-oxide coating onto an optical fiber core is presented. Indium-oxide permits the guided light in the fiber to be coupled from its core to its coating, creating resonances in the infrared and visible regions. These resonances vary as a function of the external medium's refractive index, enabling the fabrication of robust and highly reproducible wavelength-based optical fiber refractometers. Moreover, two differentiated resonances have been obtained from the same device within the 500to 1700-nm spectrum. The central wavelength of the resonances can be adjusted by varying the thickness of the indium-oxide coating. The sensitivity of the dual-peak resonance-based refractometers is within the same order of magnitude when the resonances are situated in the same spectral region. The refractometers that we obtained showed a sensitivity of 4068-nm/refractive index unit (RIU) in the range 1.333-1.392 RIU, comparable to existing ones based on resonances and other techniques, with the advantage of permitting the realization of dual-peak reference measurements in different regions of the spectrum.
    IEEE Photonics Technology Letters 01/2011; 22(24-22):1778 - 1780. DOI:10.1109/LPT.2010.2082517 · 2.18 Impact Factor
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