Efficient Tm:LiYF4 Lasers at ${\sim}2.3~\mu$ m: Effect of Energy-Transfer Upconversion
Résumé
The 3 H 4 → 3 H 5 transition of Thulium ions (Tm 3+), which features laser emission at ∼2.3 µm is studied in details. We revise the conditions for efficient laser operation using a rate-equation model accounting for the ground-state bleaching , cross-relaxation and energy-transfer upconversion (ETU). We show that ETU has a crucial role in reaching more than unity pump quantum efficiency (QE) for ∼2.3 µm Tm lasers based on highly-doped crystals. A Ti:Sapphire pumped quasi-continuous-wave 3.5 at.% Tm:LiYF 4 laser generated 0.73 W at 2306 nm with a record-high slope efficiency of 47.3% (versus the absorbed pump power, for double-pass pumping) featuring a QE of 1.27. Diode-pumping of this crystal yielded a peak output power of >2 W. The first 2.3 µm Tm waveguide laser is also reported based on Tm:LiYF 4 epitaxial layers with even higher doping of 6.2 at.% generating 0.23 W with a slope efficiency of 19.8%. The spectroscopic properties of Tm:LiYF 4 relevant for the ∼2.3 µm laser operation are revised as well. Index Terms-Solid-state lasers, laser transitions, mid-infrared, spectroscopy.
Domaines
Optique [physics.optics]Origine | Fichiers produits par l'(les) auteur(s) |
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