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 Er3+, Dy3+-doped and Er3+/Dy3+-codoped multicomponent borotellurite glasses in the composition (50-x-y) B2O3-10 TeO2-10 PbO-10 ZnO-10 Li2O-10 Na2O-(x) Er2O3- (y) 0.5 Dy2O3 ((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 Er3+ and Dy3+-doped samples, Judd-Ofelt (J-O) parameters, Ωt, were calculated following the absorption spectra and the derived Ωt parameters are utilized to predict respective radiative features for these glasses. The PL spectra of the Er3+ and Dy3+ singly doped glasses, excited at 378 nm (Er3+: 4I15/2 → 4G11/2) and 350 nm (Dy3+: 6H15/2→4M15/2,6P7/2), show important green and yellow emission bands at wavelengths 554 nm (Er3+: 4S3/2→4I15/2) and at 574 nm (Dy3+: 4F9/2→6H13/2), respectively. The PL decay curves for Er3+: 4S3/2 level and Dy3+: 4F9/2 level follow single exponential, and non-exponential nature, respectively, for the singly Er3+ and Dy3+-doped samples. For singly 1.0 mol% Er3+ and 0.5 mol% Dy3+-doped samples, the evaluated stimulated emission cross-sections (σPE) for the transitions at λem. = 0550 nm, and 574 nm are equal to 20.923×10-20 cm2 and 0. 526×10-20 cm2, while the gain bandwidths are 3.975×10-25 cm3 and 0.789×10-26 cm3, respectively. For all the Er3+-containing glasses, a broad NIR emission band centered at 1.532 μm (4I13/2→4I15/2) is noticed under both 808 and 980 nm laser diode (LD) excitations, whereas the singly 1.0 mol% Er3+-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 (σPE) of 1532 nm NIR emission when pumped by 980 nm is 2.669×10-20 cm2 and gain per unit length is 1.06×10-23 cm2s, for singly 1.0 mol% Er3+-doped glass. Additionally, for Er3+/Dy3+-codoped samples, with the decrement of Er3+: NIR emissions, energy transfer (ET) from Er3+→Dy3+ ions is identified upon both 808 and 980 nm LD pumping. For all Er3+/Dy3+-codoped glasses, the Er3+: 4I13/2 level decay time decreased with increasing Dy2O3 content and the NIR fluorescence decay curves exhibit single exponential nature. Under 980 nm excitation, the computed energy transfer efficiency (ηET) from Er3+: 4I13/2 to Dy3+: 6H11/2 level is 22.9% for the 1.0 Er3+/0.5 Dy3+ (mol%)-codoped glass. Under 808 and 980 nm pumping, the mechanism of the ET processes between Er3+ and Dy3+ ions was discussed in detail. Further, for 1.0 mol% Er3+ singly doped sample, a theoretical gain coefficient value of 17.01 dB/cm is obtained with an excited Er3+ 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.