Optical properties of Ho3+ ions in lead phosphate glasses

Ho3+-doped lead phosphate (P2O5 + K2O + Al2O3 + PbO + Na2O + Ho2O3) glasses have been prepared by conventional melt quenching technique. The optical properties have been characterized through absorption, emission and gain spectra and decay rate analysis. A strong dependence of the Ω2 parameter on the hypersensitive transition has been noticed. Using the Judd-Ofelt intensity parameters, various radiative properties like transition probabilities, branching ratios and radiative lifetimes for various emission levels has been evaluated. The radiative lifetime for the 5S2(5F4) fluorescent level and peak stimulated emission cross-section for the 5S2(5F4) → 5I8 transition are found to be 330 μs and 1.43 × 10−20 cm2, respectively. Using the McCumber theory, absorption and emission cross-sections for the 5I7 → 5I8 transition (∼2.0 μm) of the Ho3+ ion have been obtained and gain spectra are also computed as a function of population inversion. The peak stimulated emission cross-section and gain coefficient for Ho3+-doped lead phosphate glasses have been compared with other reported Ho3+:systems. The analysis indicates that these Ho3+:glasses exhibit relatively better properties for application in mid-infrared lasers at a wavelength of about 2.0 μm.

Ho3+-doped lead phosphate glasses have been prepared. The dependence of optical properties on glass composition has been studied and results show that the radiative transition probability, lifetime, branching ratio, emission cross-section, gain coefficient etc., have been affected significantly with different oxide network modifiers. In the present study, the experimental value of βR for the 5S2(5F4) → 5I8 lasing transition is found to be 0.53 which is higher compared to other transitions and is quite useful to design a green emitting laser. The figure shows emission spectra of the studied glasses.Figure optionsDownload high-quality image (113 K)Download as PowerPoint slideHighlights
► Strong dependence of Ω2 parameter on hypersensitive transition has been confirmed.
► Observed high emission cross-section and branching ratio for 5S2(5F4) → 5I8 transition.
► Decay rates of 5S2(5F4) level found single exponential for all Ho3+ ion concentrations.
► High gain coefficient of 5I7 → 5I8 transition indicates utility in mid-infrared laser devices.