Fiber probes for near- and mid-infrared spectroscopy

ABSTRACT Recent developments of specialty silica and non-silica optical fibers in synergy withinnovative designs of fiber catheters, bundles and probes have promoted the growth of variousfiber applications. There are three main areas of fiber usage: telecommunications, fibersensing and assisted remote spectroscopy and laser power delivery. This paper briefly reviewsonly the exciting area of fiber applications to remote specroscopy. SPECIALTY OPHCAL FIBERS Lu contrast with telecom fibers, where the commercial technology of standard silica fibershas essentially reached the level of intrinsic optical losses at several wavelengths and the costof these fibers is less than 10 cents per meter, specialty optical fibers for various otherapplications are still in the dramatic, early stages of development of their manufacturingtechnologies and engineering design. Silica and non—silica fibers for laser power delivery inmedical and commercial applications have been reviewed in other conferences, but the maintypes and their properties are mentioned here for comparison with specialty fibers for remotespectroscopy.The family of fibers for laser power delivery consists of large—core pure silica fibers, rareearth doped "laser" fibers and several types of non—silica ifi—fibers; namely, chalcogenidefibers, fluoride and chalcogenide glass fibers, polycrystalline silver and thallium halide fibers,single crystall sapphire fibers and the hollow metal and dielectric waveguides. The specificfeatures of these specialty fibers are determined by their application demands. They mustpossess not only minimal optical losses at laser wavelengths, but also a high threshold for laser