Efficient Tm:LiYF4 Lasers at ${\sim}2.3~\mu$ m: Effect of Energy-Transfer Upconversion

Pavel Loiko (1) , Remi Soulard (1) , Lauren Guillemot (1) , Gurvan Brasse (1) , Jean-Louis Doualan (1) , Alain Braud (1) , Aleksey Tyazhev (2) , Ammar Hideur (2) , Frédéric Druon (3) , Patrice Camy (1)

1 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique
2 CORIA - Complexe de recherche interprofessionnel en aérothermochimie
3 Laboratoire Charles Fabry / Lasers

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.

Mots clés: Solid-state lasers; laser transitions; mid- infrared; spectroscopy

Domaines: Optique [physics.optics]

Pavel Loiko, Remi Soulard, Lauren Guillemot, Gurvan Brasse, Jean-Louis Doualan, et al.. Efficient Tm:LiYF4 Lasers at ${\sim}2.3~\mu$ m: Effect of Energy-Transfer Upconversion. IEEE Journal of Quantum Electronics, 2019, 55 (6), pp.1-12. ⟨10.1109/jqe.2019.2943477⟩. ⟨hal-02991525⟩