Abstract
Er3+ ion (0.5 wt%) doped telluroborate glasses were prepared with various modifier oxides through melt quenching technique. The glass samples were labeled as TBSE, TBAE, TBZE, TBCE, TBPE and TBBE corresponding to SrO, Al2O3, ZnO, CdO, PbO and Bi2O3, respectively. The effect of modifier cations on the spectroscopic properties of Er3+ ions was analyzed through FTIR, optical absorption, photoluminescence and lifetime measurements. Presence of different vibrational groups and the structural changes caused by the incorporation of various modifier ions were identified via FTIR spectra. Bonding parameter (δ) values indicate the predominant ionic nature of Er–O bond in the prepared glasses. The Judd-Ofelt (JO) parameters follow the trend of Ω2 > Ω6 > Ω4 for TBSE, TBAE, TBCE and TBPE glasses whereas TBZE, TBBE glasses posses different order such as Ω2 > Ω4 > Ω6. The visible emission spectra (excitation at 379 nm) exhibit three emission bands centered at 531, 547 and 638 nm corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of the trivalent erbium ions. Among these emission bands, the green emission is quite intense. NIR luminescence spectra were recorded by exciting at 980 nm exhibit broad emission at 1550 nm (4I13/2→4I15/2 transition). Incorporation of different modifier cations reveals significant changes in the luminescence intensity and radiative parameters of the prepared glasses. Radiative parameters such as transition probability, effective bandwidth, stimulated emission cross-section and branching ratio have been estimated for 4S3/2→4I15/2 and 4I13/2→4I15/2 transitions. Emission cross-section (σe) and the gain coefficient (G) for the 4I13/2→4I15/2 transition have been estimated through McCumber theory. Decay profile of 4S3/2 and 4I13/2 excited states of Er3+ ion is of bi-exponential nature. It indicates that more than one relaxation mechanisms are operating in decay of the excited state of Er3+ ions. Glasses containing bismuth (TBBE) are endowed with higher stimulated emission cross-section (71.74 × 10–22 cm2) and gain bandwidth product (638 × 10–28 cm3) for 4I13/2→4I15/2 transition. The present study suggests the Er3+ ions doped telluroborate glass with bismuth cation to be best candidate for green laser and broadband optical amplifier applications.
Published Version
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