GOALI: Nanostructured Sapphire Optical Fiber for Sensing in Harsh Environment

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NON-TECHNICAL DESCRIPTION: The excellent potential of sapphire optical fiber for sensing in harsh environments such as those encountered in advanced combustion-based energy generation systems for high operation efficiency and low emission has long been recognized. The lack of viable cladding on sapphire fiber for low-loss light transmission and fiber protection remains the roadblock to real-world applications. This project aims to develop a novel alumina cladding with highly organized nano-sized air channels on sapphire fiber and to understand the associated processing-structure-property-performance correlations for evanescent-field chemical sensing and measurements via a strategy of fiber coating with aluminum followed by its anodization. The success of the project has the potential to overcome the decades-old sapphire fiber cladding challenge as well as offer a myriad of opportunities to transformative sapphire fiber-optic technology especially for sensing under adverse conditions where silica fiber sensors are no longer suitable. This project is carried out in partnership between Stevens Institute of Technology and Fiberguide Industries, Inc. TECHNICAL DETAILS: The inability to fabricate stable and high-quality cladding of controlled optical properties severely hampers the design and development of sapphire fiber sensors for a host of applications, particularly in corrosive environments at high temperatures. This project aims to develop and evaluate nanostructured alumina cladding on sapphire fiber for evanescent-field chemical sensing and measurements. The main objectives are: (1) evaluation of the theoretical correlation between mode-field overlap and cladding nanostructure to guide cladding fabrication; (2) determination of the window of processing parameters for aluminum coating and anodization as well as scale-up at Fiberguide; and (3) establishment and understanding of the interplay between the cladding nanostructure and sensing performance in combustion environment using evanescent-field laser absorption and surface-enhanced Raman scattering as the detection modalities. This project is transformative in that it has the potential to resolve the bottle-neck cladding problem long-faced by sapphire fiber and that the resultant specialty optical fiber may well lead to significant development of sapphire fiber-optic technology. Furthermore, industrial partnership and international collaboration as an integral part of the research activities greatly enriches the educational and research training experiences of the doctoral, undergraduate and high-school scholars participating in this project.