Optical spectroscopy and emission properties of Ho^{3 +}-doped gadolinium calcium silicoborate glasses for visible luminescent device applications

The Ho^{3 +}-doped gadolinium calcium silicoborate glasses with the composition of 25Gd₂O₃ + 10CaO + 10SiO₂ + (55 − x)B₂O₃ + xHo₂O₃, where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%, were synthesized by well-known melt quenching method. These glasses have been characterized through physical, structural, optical, visible emission and decay curve analysis. From the absorption spectrum, Judd-Ofelt intensity parameters for 1.0 mol% Ho₂O₃ doped glass have been carried out and were used to examine radiative properties for the important visible emitting levels of Ho^{3 +} ions. The present Ho^{3 +}:glasses show strong green emission at 545 nm and red emission at 655 nm under excitation at 452 nm. The radiative decay time and stimulated emission cross-section for the (⁵S₂,⁵F₄) → ⁵I₈ transition are found to be 280 μs and 0.63 × 10^{− 20} cm², respectively. Decay curves for all the concentration of Ho^{3 +} ions exhibit non-exponential nature for (⁵S₂,⁵F₄) → ⁵I₈ transition. The decrease in decay times is due to the resonant energy transfer among the excited Ho^{3 +} ions. Hence, these results confirm that the present silicoborate glass system could be considered as a promising candidate for visible green laser applications.