High concentration Tm3+ doped TeO2-Al2O3-BaF2 glass for ~ 2 µm fiber lasers

Abstract

The high concentration Tm3+ ions doped fluorotellurate glass samples (TeO2-Al2O3-BaF2) fabricated by high-temperature fusion technique and the luminescence properties of the glass samples were examined based on absorption and fluorescence spectra to forecast the latent capability of TAFT4 glass for ~ 2 µm band fiber lasers. The thermodynamic properties of the glass samples utilized for drawing the optical fiber, internal structure and the maximum phonon energy were characterized based on the thermal stability parameter ΔT and Raman spectra, respectively. The Judd-Ofelt (J-O) intensity parameters (Ωt) was estimated from the recorded absorption spectral data, and the estimation results showed that the value of Ω2 was as high as 6.97 × 10−20 cm2. To reveal the spectral properties of TAFT4 glass sample, significant radiative parameters including spontaneous raditive transition probabilities (Arad), fluorescence branching ratios (β), radiative lifetimes (τrad), absorption and emission cross sections of Tm3+ ions excitation energy levels were determined using J-O intensity parameters. Furthermore, the calculation of the gain coefficient is included to determine its capability as a gain medium. The fluorescence decay behavior of Tm3+ ions and the energy transfer mechanism were investigated and analyzed in detail, and the macroscopic rate WET of the CR process between Tm3+ ions in TAFT4 glass was quantified by the transfer constants CD-D and CD-A. The value of WET was high up to 2073.4 × 10−20 cm3/s by estimation. As mentioned above, the fabricated TAFT4 glass sample may be a suitable gain medium that can be used for ~2 µm band fiber lasers.