Er3+/Dy3+ codoped B2O3-TeO2-PbO-ZnO-Li2O-Na2O glasses: Optical absorption and fluorescence features study for visible and near-infrared fiber laser applications

Abstract Using melt quenching method, singly Er 3+ , Dy 3+ -doped and Er 3+ /Dy 3+ -codoped multicomponent borotellurite glasses in the composition (50-x-y) B 2 O 3 -10 TeO 2 -10 PbO-10 ZnO-10 Li 2 O-10 Na 2 O-(x) Er 2 O 3 - (y) 0.5 Dy 2 O 3 ((x=0.5, 1.0; y=0); (x=0; y=0.5, 1.0); and (x=0.5; y=0.5, 1.0; x=1.0; y=0.5, 1.0)) (mol%) were synthesized. For the fabricated samples, optical absorption, photoluminescence excitation (PLE), photoluminescence (PL), near-infrared (NIR) fluorescence and decay lifetime measurements have been performed. For singly Er 3+ and Dy 3+ -doped samples, Judd-Ofelt (J-O) parameters, Ω t , were calculated following the absorption spectra and the derived Ω t parameters are utilized to predict respective radiative features for these glasses. The PL spectra of the Er 3+ and Dy 3+ singly doped glasses, excited at 378 nm (Er 3+ : 4 I 15/2 → 4 G 11/2 ) and 350 nm (Dy 3+ : 6 H 15/2 → 4 M 15/2 , 6 P 7/2 ), show important green and yellow emission bands at wavelengths 554 nm (Er 3+ : 4 S 3/2 → 4 I 15/2 ) and at 574 nm (Dy 3+ : 4 F 9/2 → 6 H 13/2 ), respectively. The PL decay curves for Er 3+ : 4 S 3/2 level and Dy 3+ : 4 F 9/2 level follow single exponential, and non-exponential nature, respectively, for the singly Er 3+ and Dy 3+ -doped samples. For singly 1.0 mol% Er 3+ and 0.5 mol% Dy 3+ -doped samples, the evaluated stimulated emission cross-sections ( σ P E ) for the transitions at λ em.  = 0550 nm, and 574 nm are equal to 20.923×10 -20  cm 2 and 0. 526×10 -20  cm 2 , while the gain bandwidths are 3.975×10 -25  cm 3 and 0.789×10 -26 cm 3 , respectively. For all the Er 3+ -containing glasses, a broad NIR emission band centered at 1.532 μm ( 4 I 13/2 → 4 I 15/2 ) is noticed under both 808 and 980 nm laser diode (LD) excitations, whereas the singly 1.0 mol% Er 3+ -doped sample shows the highest NIR emission intensity with a full-width at half maximum (FWHM) equal to ~69 and 62 nm, respectively, at these pumping wavelengths. Moreover, the calculated highest ( σ P E ) of 1532 nm NIR emission when pumped by 980 nm is 2.669×10 -20 cm 2 and gain per unit length is 1.06×10 -23 cm 2 s, for singly 1.0 mol% Er 3+ -doped glass. Additionally, for Er 3+ /Dy 3+ -codoped samples, with the decrement of Er 3+ : NIR emissions, energy transfer (ET) from Er 3+ →Dy 3+ ions is identified upon both 808 and 980 nm LD pumping. For all Er 3+ /Dy 3+ -codoped glasses, the Er 3+ : 4 I 13/2 level decay time decreased with increasing Dy 2 O 3 content and the NIR fluorescence decay curves exhibit single exponential nature. Under 980 nm excitation, the computed energy transfer efficiency (η ET ) from Er 3+ : 4 I 13/2 to Dy 3+ : 6 H 11/2 level is 22.9% for the 1.0 Er 3+ /0.5 Dy 3+ (mol%)-codoped glass. Under 808 and 980 nm pumping, the mechanism of the ET processes between Er 3+ and Dy 3+ ions was discussed in detail. Further, for 1.0 mol% Er 3+ singly doped sample, a theoretical gain coefficient value of 17.01 dB/cm is obtained with an excited Er 3+ ion fractional factor of 0.6. Following the explored visible and NIR optical results, the synthesized glasses might be useful for visible and NIR fiber lasers application.