Optimization of luminescence properties of Ln~(3+):fluorosilicate glasses to fabricate waveguides for photonics applications

摘要

Ln_2O_3-doped fluorosilicate (SNbKZF: SiO_2 - Nb_2O_5 - K_2O - ZnF_2) glasses were prepared and characterized through various spectroscopic techniques such as optical absorption, excitation and emission spectra at room temperature to derive luminescence properties of Ln~(3+) ions in these glasses. Judd-Ofelt analysis has been successfully applied to evaluate the Judd-Ofelt intensity parameters Ω_λ (X - 2,4 and 6) and in turn radiative properties such as radiative transition probabilities A_R, branching ratios β_R, radiative lifetime τ_R and stimulated emission cross-sections σ(λ_p) of the fluorescent levels of Ln~(3+) ions in titled glasses. The predicted values of τ_R and β_R from the fluorescent level to its lower lying levels have been compared with the experimental ones. The fluorescence decay rates have been measured and are found to exhibit single exponential nature at lower concentrations and turn into non-exponential at higher concentrations. The non-exponential decay rates are well-fitted to Inokuti-Hirayama model for S = 6 indicating that the nature of the energy transfer process among the Ln~(3+) ions is of dipole-dipole type. In the present work all our systematic analysis has been presented with an example of results obtained in Sm~(3+): SiO_2 - Nb_2O_5 - K_a2O - ZnF_2 glasses. These results are used to access the gain media and in turn useful not only to write waveguides but also to modify the fluorescence properties through femtosecond laser irradiation.