Ho<sup>3+</sup> doped low-phonon single crystals and chalcogenide glasses for mid-IR source application
E. Brown, Zackery D. Fleischman, Jason McKay, Larry D. Merkle, U. Hömmerich, W. Pałosz, Sudhir Trivedi, Mark Dubinskii
Abstract
A comparative study was conducted to investigate the 3.9 µm mid-IR emission properties of Ho 3+ doped NaYF 4 and CsCdCl 3 crystals as well as Ho 3+ doped Ga 2 Ge 5 S 13 glass. Following optical excitation at ∼890 nm, all the studied materials exhibited broad mid-IR emissions centered at ∼3.9 µm at room temperature. The mid-IR emission at 3.9 µm, originating from the 5 I 5 → 5 I 6 transition, showed long emission lifetime values of ∼16.5 ms and ∼1.61 ms for Ho 3+ doped CsCdCl 3 crystal and Ga 2 Ge 5 S 13 glass, respectively. Conversely, the Ho 3+ doped NaYF 4 crystal exhibited a relatively short lifetime of ∼120 µs. Temperature dependent decay time measurements were performed for the 5 I 5 excited state for all three samples. The results showed that the emission lifetimes of Ho 3+ :CsCdCl 3 and Ho 3+ :Ga 2 Ge 5 S 13 were nearly temperature independent over the range studied, while significant emission quenching of the 5 I 5 level was observed in Ho 3+ :NaYF 4 . The temperature dependence of the multi-phonon relaxation rate for 3.9 µm mid-IR emission in Ho 3+ :NaYF 4 crystal was determined. The room temperature stimulated emission cross-sections for all three samples were calculated using the Füchtbauer-Landenburg equation. Furthermore, the results of Judd-Ofelt analysis are presented and discussed.