Fiber-optic-based sensors have been applied to a variety of remote sensing problems: measurement of pressure, humidity, vapor-phase chemicals, and aqueous biomolecules are leading examples.[1-6] With a width of only a few tens to hundreds of microns, these sensors require little power to operate, are impervious to electrical interference, and can be multiplexed together into distributed sensor configurations.[2,4,5] Fiber sensors may be extrinsic or intrinsic, depending on how the measured parameter is optically transduced; intrinsic sensors, like interferometric and Fabry-Perot cavity devices, leverage the fiber's inherent optical properties to transform a parameter such as mechanical stress into an optical signal.[3,7,8] Extrinsic sensors, such as bead-based arrays and polymer caps, immobilize an indicator or label on the distal end of the fiber, using only the light-carrying capability of the fiber to transduce the sensor signal. In this work, an extrinsic sensor for volatile organic compounds (VOCs) is created by adhering a 0.5 mm-diameter porous Si photonic crystal to an optical fiber. Remote sensing with such a device is demonstrated by detecting breakthrough of VOCs in an activated carbon filtration bed.
M. J. Sailor, Department of Chemistry and Biochemistry, University of California - San Diego, La Jolla, CA 92093 (USA)