Tunable continuous-wave laser operation of Tm3+:BaY2F8 near 2.3 µm

4.1 W continuous-wave and broadly wavelength tunable Tm-doped laser in 2.1-2.4 µm spectral region based on vibronic and electronic transitions

Efficient diode-pumped continuous-wave (CW) and wavelength tunable Tm:YAP lasers based on the vibronic and electronic transitions are investigated. A total maximum output power of 4.1 W is achieved with multi-wavelength output around 2162 nm and 2274 nm, corresponding to a slope efficiency of 29.8% for a 3 at. % Tm:YAP crystal. A maximum output power of 2.48 W with a slope efficiency of 25.4% is obtained at 2146 nm for a 4 at. % Tm:YAP crystal. Using a birefringent filter (BF), the emission wavelengths of the Tm:YAP laser are tuned over spectral ranges of 59 nm from 2115 nm to 2174 nm and 127 nm from 2267 nm to 2394 nm, respectively, which is the first demonstration of wavelength tunable Tm:YAP laser based on the electronic transition 3H4→3H5 and vibronic transition 3F4→3H6, to the best of our knowledge. The results show great potentials of the Tm:YAP crystal for realizing efficient lasers in the spectral range of 2.1-2.4 µm.

Broadly tunable continuous wave 2.3-µm Tm3+:tellurite bulk glass laser

We report, for the first time to the best of our knowledge, a continuous wave trivalent thulium ion (Tm3+)-doped bulk glass near 2.3 µm. In the experiments, a bulk Tm3+-doped tellurite glass with the stoichiometric composition of 74TeO2-12ZnO-4La2O3-10Na2O (Tm3+:TZLN) was used. Lasing operation was achieved by using an x-fold cavity at the free-running wavelength of 2303 nm. The maximum slope efficiency of 6.2% was obtained with respect to the absorbed pump power with a 1% transmitting output coupler. In this case, as high as 100-mW output power was generated with 2.2 W of absorbed pump power. Continuous, broad tuning was achieved from 2233 nm to 2400 nm. The excitation spectrum of the laser was also investigated and 2.3-µm lasing was obtained by varying the pump wavelength over the 773-809-nm range. The absorption cross section was determined to be 4.4 × 10-21 cm2, based on open-aperture z-scan measurement. By using the laser efficiency data, the emission cross section of the Tm3+:TZLN glass was further determined to be 1.3 × 10-20 cm2 at 2.3 µm.

Watt-level diode-pumped Tm:YVO4 laser at 2.3 µm

In this Letter, a watt-level laser diode (LD)-pumped ∼2.3-µm (on the ³H₄→³H₅ quasi-four-level transition) laser is reported based on a 1.5 at.% a-cut Tm:YVO₄ crystal. The maximum continuous wave (CW) output power obtained is 1.89 W and 1.11 W with the maximum slope efficiency of 13.6% and 7.3% (versus the absorbed pump power) for the 1% and 0.5% transmittance of the output coupler, respectively. To the best of our knowledge, the CW output power of 1.89 W we obtained is the highest CW output power amongst the LD-pumped ∼2.3-µm Tm³⁺-doped lasers.