Eu³⁺ doped Bi₄Ge₃O₁₂ fiber single crystals grown by the micro-pulling-down method

The Eu³⁺ doped Bi₄Ge₃O₁₂ (BGO) fiber single crystals were successfully grown by the micro-pulling-down method with the resistance heating system. The Eu³⁺ doping concentration in the starting melt was varied from 0.1 to 0.6mol%. For the Eu³⁺ 0.1 and 0.2mol% doped BGO fiber crystal, the best fiber single crystals were obtained for a pulling-down rate equal to 0.08mm/min. The grown fiber crystals from these compositions were transparent and nearly colorless except for a slight yellowish tint at the end of the fibers. To investigate the homogeneity of the grown fibers, distribution coefficient of the Eu ion was measured.