A highly efficient milli-joule-level Q-switched Tm,La:CaF2 laser is experimentally demonstrated. By employing an acousto-optic modulator, the diode-pumped pulsed lasers are stably operated at repetition rates ranging from 500 Hz to 10 kHz. Dual-wavelength operation of 1881.7 nm and 1888.5 nm is achieved with slope efficiency of 64.7%. Up to 1.89 mJ of pulse energy is obtained at a pulse width of 100 ns, corresponding to a peak power of 18.88 kW. These results verified that the Tm,La:CaF2 crystal could be a promising candidate for achieving highly efficient and high-energy pulsed lasers.

The population trapping effect of the F34 level is an important factor limiting the power scaling of the 2.3 μm thulium (Tm) laser on the H34→H35 transition. In this Letter, we demonstrate a novel scheme of ground state absorption (GSA) (H36→H34) and excited state absorption (ESA) (F34→H34) dual-wavelength pumped 2.3 μm Tm lasers. Introducing an ESA pumping process can accurately excite the Tm3+ ions accumulated in the F34 level to the H34 level, constructing a double populating mechanism for the upper laser level H34. A proof-of-principle experimental demonstration of the GSA (785 nm) and ESA (1470 nm) dual-wavelength pumped 2.3 μm Tm:LiYF4 (Tm:YLF) laser was realized. A maximum continuous-wave output power of 1.84 W at 2308 nm was achieved under 785 and 1470 nm dual-wavelength pumping, increased by 60% compared with the case of 785 nm single-wavelength pumping under the same resonator condition. Our work provides an efficient way to achieve higher output power from 2.3 μm Tm-doped lasers on the H34→H35 transition.