A chemical sensor system consisting of a coated long period grating, which was spliced into a fiber loop cavity, has been prepared and characterized. Designer coatings based on polydimethylsiloxane and nanostructured organically modified silica (ORMOSIL) materials were prepared to provide enhanced sensitivity for a variety of key environmental pollutants. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change of the attenuation spectrum of the long period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and laser power fluctuations. Chemical differentiation of cyclohexane and xylenes was achieved and a detection limit of 300 ppm of xylenes vapour in air was readily realized for PDMS coatings. Ormosil-type coatings were capable of detecting lead cations at concentrations below 1 ppm in water.

Date Published: 12 August 2008
PDF: 8 pages
Proc. SPIE 7099, Photonics North 2008, 70992C (12 August 2008); doi: 10.1117/12.806722

Published in SPIE Proceedings Vol. 7099:
Photonics North 2008