Fabrication and properties of rare‐earth‐doped optical fiber using barium as an alternate codopant

Abstract

Barium has been established as an alternate codopant other than conventional aluminum or phosphorous for fabrication of rare-earth-(RE) doped optical fiber through modified chemical vapor deposition (MCVD) coupled with solution doping technique. Different optical and material characterization results of our fabricated fibers indicate potential application as amplifier and laser. The amplifier performance of Er-doped fiber and lasing as well as photo darkening (PD) experiment of Yb-doped fiber doped with BaO is presented where Ba serves as an alternate candidate for enhancement of RE solubility in silica glass.

The uniqueness of glass for passive thermal management for optical fibers

“…37 BaO-doped silica optical fibers have been fabricated using MCVD and reported to exhibit better photodarkening performance in comparison with the conventional aluminosilicate fibers. 38,39 Doping of BaO into SiO 2 is limited by a subsolidus immiscibility, which ranges from least 2 to 28 mol% BaO with upper consolute point of 10 mol% BaO and temperature of 1460 • C. 40 For a glass to be formed, the critical cooling rate needed to exceed about 10 3 K/s, 41 which is commensurate with that for fiber drawing. When BaO has been (solution) doped into silica preforms using the MCVD process, concentrations of <2 mol% were realized due to phase separation at the processing conditions.…”

“…When BaO has been (solution) doped into silica preforms using the MCVD process, concentrations of <2 mol% were realized due to phase separation at the processing conditions. 38 The purpose of this section was to explain the general compositional limits of CVD-derived optical fibers, which are summarized in Table 1 relative to other common specialty optical fiber fabrication methods. With this established, the sections that follow provide descriptions for how fiber compositions can be practically used to intrinsically (passively) help manage thermal effects in active fiber lasers and amplifiers.…”

“…As a second illustration, consider the BaO–SiO 2 system, which has been studied at least as far back as 1922 37 . BaO‐doped silica optical fibers have been fabricated using MCVD and reported to exhibit better photodarkening performance in comparison with the conventional aluminosilicate fibers 38,39 . Doping of BaO into SiO 2 is limited by a subsolidus immiscibility, which ranges from least 2 to 28 mol% BaO with upper consolute point of 10 mol% BaO and temperature of 1460°C 40 .…”

“…For a glass to be formed, the critical cooling rate needed to exceed about 10 3 K/s, 41 which is commensurate with that for fiber drawing. When BaO has been (solution) doped into silica preforms using the MCVD process, concentrations of <2 mol% were realized due to phase separation at the processing conditions 38 …”