An optical fiber long-period grating sensor for organic vapors utilizing a ZnO nanorod out-cladding

The authors present a novel organic vapor sensor based on a LPG overlaid with a zinc oxide (ZnO) nanostructured film. The sensing probe has been designed for operating at room temperature while being interrogated at the 1.5 μm band. The ZnO chemosensitive layer, developed onto the cladding area of the LPG, consists of random nanorods with a characteristic diameter of 100 nm, that were grown in an aqueous solution of Zn(NO₃)₂ and ammonia at 80°C, following pulsed laser deposition of a thin metallic Zn layer on the fibers. For optimizing the nanostructured ZnO layer thickness with respect to the optical design and thus the sensitivity of the device, the authors monitored in real-time the spectrum of the LPGs during the ZnO chemical growth process; targeting specific spectral characteristics of the composite grating structure.