Enhanced mid-infrared 2.7 μm luminescence in low hydroxide bismuth-germanate glass and optical fiber co-doped with Er3+/Yb3+ ions

In this article, low hydroxide bismuth-germanate glasses doped with Er3+ and co-doped with Er3+/Yb3+ ions have been synthesized. The fabricated host was characterized by high thermal stability parameter (Delta T = 125 degrees C), high transmittance in mid-infrared region and low maximum phonon energy (724 cm(-1)). In order to reduce OH- ions impact on the transmittance value at the band of 3.1 mu m, the modified synthesis process has been conducted in low vacuum conditions (50-70 mbar). The wide transmittance window from 0.515 to 5.5 mu m has been determined in terms of optical parameters. Luminescent properties of Er3+ ions indicated increase of luminescence intensity at the wavelength of 2.7 mu m (I-4(11/2) -> I-4(13/2)) under 980 nm laser diode excitation resulting from OH- reduction. Simultaneously, the addition of ytterbium to glass system has increased emission intensity in mid-infrared band due to Yb3+ -> Er3+ energy transfer. According to mid-infrared luminescence measurements, molar ratio of co-dopants in developed glass matrix for the maximum emission intensity has been determined. Glass characterized by the highest mid-IR emission intensity has been used as the active core of produced optical fiber. (C) 2016 Elsevier B.V. All rights reserved.