Modeling visible and infrared stimulated emission from Tb³⁺in TbAlO 3

With recently developed diode-lasers to resonantly pump solid-state crystalline lasers, new opportunities arise for systems such as Tb³⁺ as an activator ion in different host matrices. For example the observed fluorescence from ⁵D₄→ ⁷F₅ transition (540 to 560 nm) of Tb³⁺ in TbAlO₃ represents such a possibility. There is little fluorescence quenching in this crystal involving this transition, and the measured lifetime is approximately 2 ms, long enough to sustain sufficient population for stimulated emission. The quantum efficiency is better than 50 % as measured in this material. For this same transition, others have reported room-temperature pulsed laser operation at 544 nm for Tb:YLF, where the lifetime is comparable. Mid- and long wavelength infrared laser emission has been observed for Tb³⁺ in chalcogenide glass fibers that complement our spectroscopic findings for Tb³⁺ in pedestal-grown Y₂O₃ and YAG fibers. We have identified the infrared transitions that may lase at transitions between different manifolds within the ⁷F_J multiplet. In the present study we first evaluate the various visible and infrared experimental findings with a Judd-Ofelt analysis of Tb³⁺ in TbAlO₃. We predict a radiative lifetime of 3.5 ms for the excited ⁵D₄ manifold to the ⁷F_J manifolds with more than 50% of the emission represented by the ⁵D₄→ ⁷F₅ transition. To account for the visible stimulated emission, we report transition probabilities for ⁵D₄→ ⁷F_J transitions and for diode-pumped infrared transitions we report similar spectroscopic properties for transitions within the ⁷F_J multiplet.

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