Comprehensive phase analysis of GaAs:(Cu, Au) systems in molten core fibers

The recently developed “flux assisted molten core method,” used previously to fabricate GaAs core fiber with Sn as a solvent phase, is further extended here to Cu and Au fluxes. Unlike the GaAs:Sn system whose observed phases were the same in the precursor, as-drawn, and laser annealed fiber, the GaAs:Cu and GaAs:Au systems exhibited differing phases at each stage of the process. These systems undergo reactions during the molten core fiber fabrication and CO2 laser post-processing. X-ray diffraction is employed to determine the phases resulting from As volatility during the pre-melt, fiber draw, and CO2 laser post-processing. The phases, while unanticipated, are determined to be thermodynamically stable. In some of the systems, remnant Ga is suggested as being located in the flux compounds. This is a break with the conventional molten core method, where the fiber consists of the same phases as the starting material, and cases where reactions are driven in the molten core. The volatility of GaAs brings about unexpected reactions.