Survey of optical and fluorescence traits of Tm3+-doped alkali/mixed alkali oxides constituting B2O3-BaO-ZnO-LiF glasses for 0.45 μm laser and 1.46 μm fiber amplifier

Abstract

For six 1 mol% Tm3+-doped B2O3-BaO-ZnO-LiF glasses containing single and mixed alkali oxides (fabricated by melt-cast approach), optical absorption, and visible and near-infrared (NIR) fluorescence features including visible luminescence decay times were explored. Optical band gaps, Urbach energy, and two-photon absorption coefficients were evaluated for all studied glasses. Judd–Ofelt (J–O) analysis from absorption spectra was performed to compute Tm3+: 4f–4f transitions J–O parameters Ωλ (λ = 2, 4, 6), and utilizing Ω2, Ω4 and Ω6 values radiative transition probabilities (AR), branching ratios (βR), and radiative lifetimes (τR) for all Tm3+ ion's excited levels were assessed. For obtained intense blue emission band (454 nm) upon 358 nm excitation, various parameters considered in developing visible laser systems were calculated. Tm3+: Na ions having sample exhibits high AR, highest peak emission cross-section (σmaxem) (=5.89 × 10–21 cm2) and gain bandwidth(σmaxem × Δλeff) (=9.69 × 10–27 cm3) for 1D2→3F4 luminescence transition in all glasses for a favorable blue lasing process. All emission decay curves of the 1D2 upper level showed nonexponential nature. Commission Internationale de l'éclairage (CIE) coordinates, color purity, and luminous efficiency of radiation were derived from visible fluorescence spectra, and attained CIE (x,y) coordinates values reflect the purplish-blue light region. Under direct optical pumping of 3H6→3H4 transition using 808 nm laser diode, NIR fluorescence spectra exhibit a wideband within 1.3–1.6 μm spectral range peaked at 1.46 μm (3H4→3F4 transition). NIR emissions effective bandwidth (Δλeff) was varied relying on different alkali oxides. Δλeff ~ 121 nm was deduced for Tm3+: Li ions comprising glass with large σmaxem (=1.832 × 10–21 cm2), high(σmaxem × Δλeff) (=2.22 × 10–26 cm3), and optical gain (=12.608 × 10–25 cm2s) for 3H4→3F4 emission transition and its gain profile wraps the entire S-optical communication band range for efficient broadband amplification purpose in wavelength-division multiplexing systems. © 2021 The Author(s)