@article{331a8d514e714b369ec0039bd912f91b,
title = "On the fabrication of all-glass optical fibers from crystals",
abstract = "The highly nonequilibrium conditions under which optical fibers conventionally are drawn afford considerable, yet underappreciated, opportunities to realize fibers comprised of novel materials or materials that themselves cannot be directly fabricated into fiber form using commercial scalable methods. Presented here is an in-depth analysis of the physical, compositional, and selected optical properties of silica-clad erbium-doped yttrium aluminosilicate glass optical fibers derived from undoped, 0.25, and 50 wt % Er3+ -doped yttrium aluminum garnet (YAG) crystals. The YAG-derived fibers were found to be noncrystalline as evidenced by x-ray diffraction and corroborated by spectroscopic measurements. Elemental analysis across the core/clad interface strongly suggests that diffusion plays a large role in this amorphization. Despite the noncrystalline nature of the fibers, they do exhibit acceptable low losses (∼0.15-0.2 dB/m) for many applications, broad-band emissions in the near-infrared, and enhanced thermal conductivity along their length while maintaining equivalent mechanical strength with respect to conventional silica optical fibers. Further, considerably higher rare-earth doping levels are realized than can be achieved by conventional solution or vapor-phase doping schemes. A discussion of opportunities for such approaches to nontraditional fiber materials is presented.",
author = "J. Ballato and T. Hawkins and P. Foy and B. Kokuoz and R. Stolen and C. McMillen and M. Daw and Z. Su and Tritt, {T. M.} and M. Dubinskii and J. Zhang and T. Sanamyan and Matthewson, {M. J.}",
note = "Funding Information: This work was supported in part by the Joint Technology Office (JTO) through their High Energy Laser Multidisciplinary Research Initiative (HEL-MRI) programs at Clemson University: “High Power Fiber Lasers” under an ARL supplement to USARO under Contract No. W911NF-05-1-0517 and “Eye-Safe Polycrystalline Lasers” under USAFOSR under Contract No. FA9550-07-1-0566. Additionally, the authors wish to thank Northrop Grumman-Synoptics (Charlotte, NC) for providing at no cost the undoped and doped YAG samples, Dr. Bob Rice of Northrop Grumman Space Technology (Redondo Beach, CA) for insightful comments, and Dr. Larry McCandlish of Ceramare (Piscataway, NJ) for core-drilling the YAG samples. FIG. 1. Optical (a) and electron microscopic (b) images of different representative fibers drawn from a YAG starting core crystal. The optical micrograph (a) is of a fiber with a 125 μ m outer diameter. The electron micrograph (b) is of a fiber drawn to a diameter such that the core was about 250 μ m . The points marked across the core region (b) indicate where elemental analysis was performed (see Figs. 6–8 ). FIG. 2. Spectral attenuation of the undoped and lightly doped ( 0.25 wt % Er:YAG in the preform) “YAG-core” fiber. Absorption band peaked at 1385 nm is due to OH groups in the as-grown crystal. FIG. 3. Core absorption spectrum of the fiber drawn from the preform containing a 0.25 wt % Er:YAG crystal; 1 nm spectral resolution. Absorption peak at 1385 nm is also attributed to residual water absorption from the as-grown crystal. FIG. 4. Normalized absorption spectrum of the optical fiber derived from the Er:YAG containing preform compared to that for a YAG single crystal and two commercial EDFA fibers. FIG. 5. Spectroscopic properties of the fiber drawn using the 0.25 wt % Er:YAG crystal in the core: (a) fluorescence corrected for spectral response of the spectrometer overlaid with the absorption of the fiber; (b) fluorescence kinetics of the 0.25 wt % Er 3 + -doped fiber measured at 1532.5 nm with the ∼ 10 ns pulse excitation at 532 nm. FIG. 6. Elemental profiles (relative elemental composition as a function of position across the fiber) for the undoped fiber. The figures (a), (b), and (c) were drawn to core sizes of 230, 191, and 57 μ m , respectively. FIG. 7. Elemental profiles (relative elemental composition as a function of position across the fiber) for the for drawn from a preform containing 0.25 wt % Er:YAG. The figures (a), (b), and (c) were drawn to core sizes of 369, 248, and 24 μ m , respectively. Note that the erbium concentration is too small to be measurement in this particular experiment. FIG. 8. Elemental profiles (relative elemental composition as a function of position across the fiber) for drawn from a preform containing 50 wt % Er:YAG. The figures (a), (b), and (c) were drawn to core sizes of 600, 500, and 260 μ m , respectively. FIG. 9. Silicon concentration (indicating SiO 2 content) in the center of the fiber core taken from the data of Figs. 6–8 . The lines are guides for the eyes. FIG. 10. Thermal conductivity as a function of temperature measured along the fiber length. FIG. 11. Weibull probability plot of the strength of undoped fiber measured in two-point bending at four different faceplate speeds. FIG. 12. Weibull probability plot of the strength of fiber drawn from the 50% Er:YAG containing preform measured in uniaxial tension at a stress rate of 30 MPa/s. ",
year = "2009",
doi = "10.1063/1.3080135",
language = "English (US)",
volume = "105",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "5",
}