Sol–gel derived coating applied to long-period gratings for enhanced refractive index sensing properties

Edward Davies, Reeta Viitala, Mikko Salomäki, Sami Areva, Lin Zhang, Ian Bennion

Research output: Contribution to journalArticlepeer-review


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.
Original languageEnglish
Article number015501
Pages (from-to)015501
Number of pages1
JournalJournal of Optics A
Issue number1
Publication statusPublished - Dec 2008


  • photonics
  • sensors
  • instrumentation and measurement
  • optics
  • quantum optics and lasers
  • condensed matter


Dive into the research topics of 'Sol–gel derived coating applied to long-period gratings for enhanced refractive index sensing properties'. Together they form a unique fingerprint.

Cite this