Enhanced spectral sensitivity of fibre long period gratings to refractive index of aqueous solutions utilising copper patterned coatings


A set of long period grating devices have been fabricated in photosensitive single mode fibre coated with a series of copper rings (period of 380μm, 50% duty cycle and length of 4cm). The long period gratings were inscribed with a uniform UV-laser exposure across the entire length of the copper ring patterned coating. The devices ranged in copper thickness from 0.5μm to 1.5μm. In addition, a control long period grating was fabricated in the same type of fibre with the same period for comparison. The refractive index and temperature spectral sensitivity of these devices were investigated and it was found that the index and temperature sensitivity is a function of the thickness of the copper rings, as supported by theoretical modelling. Furthermore, the index sensitivity of these devices in the 1.333 index region is greater than the control long period grating. The patterned 0.5μm coated long period grating gave a sensitivity of Δλ/Δn = -74 nm leading to a resolution of 1.4×10-3 compared to the control which had a sensitivity of Δλ/Δn = -32 nm with a resolution of 3.2×10-3 in the index region of 1.320 to 1.380 (aqueous solution regime). This demonstrates a two fold increase in the sensitivity. This novel fibre long period grating device shows potential for increasing the resolution of measurements of the index of aqueous solutions.

Publication DOI: https://doi.org/10.1117/12.647515
Divisions: College of Engineering & Physical Sciences > Aston Institute of Photonics Technology (AIPT)
Additional Information: Allsop, Thomas; Dobb, Helen L.; Neal, Ron; Kalli, Kyriacos; Themistos, Christos; Rahman, B.M.A.; Webb, David; Mapps, Des J.; Bennion, Ian, "Enhanced spectral sensitivity of fibre long period gratings to refractive index of aqueous solutions utilising copper patterned coatings." Optical fibers and sensors for medical diagnostics and treatment applications VI. ed. / Israel Gannot. Vol. 6083 SPIE, 2006. Copyright 2006 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. http://dx.doi.org/10.1117/12.647515
Event Title: Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications VI
Event Type: Other
Event Dates: 2006-01-21 - 2006-01-22
Uncontrolled Keywords: index sensing,long period gratings,coatings,Engineering(all)
ISBN: 0-8194-6125-3, 978-0-8194-6125-4
Last Modified: 03 Jan 2024 18:14
Date Deposited: 25 Jan 2013 10:33
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://spiedigi ... 6083/1/60830S_1 (Publisher URL)
PURE Output Type: Conference contribution
Published Date: 2006-05-08
Authors: Allsop, Thomas D.P. (ORCID Profile 0000-0001-8905-9014)
Dobb, Helen L.
Neal, Ron
Kalli, Kyriacos
Themistos, Christos
Rahman, B.M.A.
Webb, David (ORCID Profile 0000-0002-5495-1296)
Mapps, Des J.
Bennion, Ian



Version: Published Version

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