Optical properties, fluorescence mechanisms and energy transfer in Tm 3+, Ho 3+ and Tm 3+ -Ho 3+ doped near-infrared laser glasses, sensitized by Yb 3+

Abstract

The optical properties of the rare elements Tm 3+, Ho 3+ and Yb 3+ were systematically investigated in various glasses. The Tm 3+ doped aluminozircofluoride glass shows higher quantum efficiency, longer lifetime and stronger fluorescence intensity than Tm 3+ doped YSGG crystal and other Tm 3+ doped glasses for the 3 H 4 → 3 H 6 transition. Similar quantum efficiency, longer lifetime and stronger fluorescence intensity were also found in Ho 3+ doped aluminozircofluoride glass for the 5 I 7 → 5 I 8 transition. The higher quantum efficiencies of Tm 3+ and Ho 3+ in aluminozircofluoride glass are due to the longer lifetime and the lower phonon energy. The fluorescence mechanisms and energy transfer in the Yb 3+ -Tm 3+ system, Yb 3+ -Ho 3+ system and Yb 3+ - Tm 3+ -Ho 3+ system were studied. The very strong fluorescence intensities in the Yb 3+ -Tm 3+ system for Tm 3+ and the Yb 3+ -Tm 3+ -Ho 3+ system for Ho 3+ which are 1.68 times that of Tm 3+ doped YSGG crystal and 2.25 times that of Tm 3+Ho 3+ codoped YSGG crystal are attributed to the efficient Yb 3+ → Tm 3+, Yb 3+ → Ho 3+ and Tm 3+ → Ho 3+ energy transfer processes. The fluorescence processes are described by cross relaxations of 2 F 5 2 → 3 H 5 → 3 H 4 → 3 H 6 → 2 F 7 2 and 2 F 5 2 → 3 H 5 (or 2 F 5 2 → 5 I 6 → 3 H 5) → 3 H 4 → 5 I 7 → 5 I 8 → 3 H 6 → 2 F 7 2 .