Fabrication And Mid-Infrared Emission Properties Of Rare Earth-Doped Selenide Chalcogenide Glass Fiber

The mid-infrared（MIR）wavelength（2-5μm）is located in the important transmission window of atmosphere,therefore the lasers working in this band has great applications in national defense,medical surgery,and environmental monitoring.The fiber laser based on the rare-earth ions doped glass fiber is one of the most potential ways to realize the MIR laser output.Among various gain fiber materials,selenide chalcogenide glasses have attracted much attention due to their low phonon energy,high refractive index and wide transmission range.In this paper,the Ge-As-Ga-Se selenide chalcogenide glass fiber doped with Pr³⁺and Dy³⁺rare-earth ions were taken as the research objects.Two series of Ge₁₂As_20.8Ga₄Se_63.2-x Pr（x=0.05,0.1,0.2,0.3,0.4 wt.%）and Ge₁₂As₂₄Ga₂Se₆₃-x Dy（x=0.05,0.1,0.2,0.3,0.4 wt.%）glasses were prepared and analyzed after the optimization of the composition and the multi-step physical and chemical purification processes.The X-ray diffraction（XRD）,field emission transmission electron microscopy（FE-TEM）,differential scanning calorimetry（DSC）and electron probe X-ray microanalysis（EPMA）were used to analyze the glass formation stability,anti-crystallization characteristics,thermal stability and the distribution of rare-earth ions.The contents of impurities in the glass were analyzed by Fourier transform infrared spectroscopy（FT-IR）and EPMA.The MIR luminescence properties of Pr³⁺,Dy³⁺ion doped selenide glasses were systematically analyzed based on UV-VIS-NIR absorption spectra,MIR fluorescence emission spectra,fluorescence lifetime and Juddy-Ofelt theory.Two optical fibers based on the Ge₁₂As_20.8Ga₄Se_63.2-0.2Pr and Ge₁₂As₂₄Ga₂Se₆₃-0.3Dy compositions,which have the strongest MIR luminescence,were designed and fabricated successfully,and their optical losses were measured by truncation method.The experimental results show that after component optimization,the maximum solubility of the matrix glass for Pr³⁺and Dy³⁺reaches 0.4 wt.%and 0.3 wt%,respectively,and good devitrification resistance was also guaranteed.The glasses have good thermal properties andΔT always maintains≥100℃.The contents of impurities in glass have been removed effectively after physical and chemical purifications.The characteristic absorption coefficient increases with the increasing of the rare-earth ions’concentration and reaches the maximum when the doping concentration of Pr³⁺is 0.4 wt.%and the doping concentration of Dy³⁺is 0.3 wt.%,respectively.The MIR emission intensity of Pr³⁺and Dy³⁺doped samples reaches the maximum when the doping concentration is 0.2 wt.%and 0.3 wt.%,respectively.Based on the J-O theory,the stimulated emission cross-sectionσ_emi of 0.2 wt.%Pr³⁺doped sample is 1.07×10^-20cm²@4.6μm and 1.19×10^-20 cm²@4.8μm,respectively.The stimulated emission cross-sectionσ_emi of the 0.3 wt.%Dy³⁺ions doped glass is 1.23×10^-20cm²@4.3μm and the measured fluorescence lifetime is 1.53ms,leading to the laser quality factor value(σ_emi×τ_mea)1.89×10^-23cm²·s.The lowest fiber loss of Ge₁₂As_20.8Ga₄Se_63.2-0.2Pr and Ge₁₂As₂₄Ga₂Se₆₃-0.3Dy glass fiber was 2.95 d B/m@6.58μm and 2.47 d B/m@8.3μm,respectively.These fibers have great potential as gain mediums for MIR lasers and amplifiers.