Long-period grating and its cascaded counterpart in photonic crystal fiber for gas phase measurement

Fei Tian, Jiri Kanka, Henry Du

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Regular and cascaded long period gratings (LPG, C-LPG) of periods ranging from 460 to 590 μm were inscribed in an endlessly single mode photonic crystal fiber (PCF) using CO2 laser for sensing measurements of helium, argon and acetylene. High index sensitivities in excess of 1700 nm/RIU were achieved in both grating schemes with a period of 460 μm. The sharp interference fringes in the transmission spectrum of C-PCF-LPG afforded not only greatly enhanced sensing resolution, but also accuracy when the phase-shift of the fringe pattern is determined through spectral processing. Comparative numerical and experimental studies indicated LP01 to LP03 mode coupling as the principal coupling step for both PCF-LPG and C-PCF-LPG with emergence of multimode coupling at shorter grating periods or longer resonance wavelengths.

Original languageEnglish
Pages (from-to)20951-20961
Number of pages11
JournalOptics Express
Volume20
Issue number19
DOIs
StatePublished - 10 Sep 2012

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