In the frame of the developpement of Raman fiber laser sources with diffraction-limited beam quality, a wavelength close to 1680 nm was used for the optical pumping of crystalline laser materials doped with Tm3+ ions. This project continued through the pumping of Tm-doped or Tm/Ho codoped LiYF4 crystals and waveguides. The objective was to demonstrate the efficiency of in-band pumping, which could also lead us to study these systems under mode-locking conditions.
Recently, we achieved efficient laser operation of a Tm:CaF2 crystal in-band pumped at 1610 nm by an Er-Yb-codoped fiber laser system. A laser slope efficiency of 55% (versus incident pump power) was achieved in a continuous-wave regime, with a maximum output power of 1.25 W at ∼1.88µm in a nearly diffraction-limited beam (M2=1.14). We also demonstrated a continuous tuning range of 180 nm, which extends to short wavelengths down to 1773 nm.
R. Thouroude, A. Tyazhev, A. Hideur, P. Loiko, P. Camy, J.L. Doualan, H. Gilles, and M. Laroche, "Widely tunable in-band-pumped Tm:CaF2 laser" Opt. Lett. 45, 4511-4514 (2020)
doi : https://doi.org/10.1364/OL.399670
P. Loiko, R. Thouroude, R. Soulard, L. Guillemot, G. Brasse, B. Guichardaz, A. Braud, A. Hideur, M. Laroche, H. Gilles, and P. Camy, "In-band pumping of Tm:LiYF4 channel waveguide : a power scaling strategy for ∼2 μm waveguide lasers," Opt. Lett. 44, 3010-3013 (2019)
doi : https://doi.org/10.1364/OL.44.003010