A1 Refereed original research article in a scientific journal
Sol-gel derived coating applied to long-period gratings for enhanced refractive index sensing properties
Authors: Davies E, Viitala R, Salomaki M, Areva S, Zhang L, Bennion I
Publisher: IOP PUBLISHING LTD
Publication year: 2009
Journal:: Journal of Optics A: Pure and Applied Optics
Journal name in source: JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS
Journal acronym: J OPT A-PURE APPL OP
Article number: ARTN 015501
Volume: 11
Issue: 1
Number of pages: 6
ISSN: 1464-4258
DOI: https://doi.org/10.1088/1464-4258/11/1/015501
Abstract
Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain, and refractive index ( RI). We report here, to the best of our knowledge, the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; a coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs' most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0 +/- 0.4) nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15 +/- 0.04) nm/uri. The experimental results also reveal that, even in the RI insensitive region around 1.33, there still is a marked enhancement in RI sensitivity of the sol-gel coated LPG compared to the uncoated one. This is potentially significant as coated LPGs may be extended to low RI gas and semi-liquidized based sensing applications.
Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain, and refractive index ( RI). We report here, to the best of our knowledge, the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; a coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs' most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0 +/- 0.4) nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15 +/- 0.04) nm/uri. The experimental results also reveal that, even in the RI insensitive region around 1.33, there still is a marked enhancement in RI sensitivity of the sol-gel coated LPG compared to the uncoated one. This is potentially significant as coated LPGs may be extended to low RI gas and semi-liquidized based sensing applications.
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