Tm:YLF laser at 1.9 μm double-end pumped by laser diode

Continuous wave (CW) Tm:YLF solid laser at 1.9 μm using laser diode (LD) double-end pumping is reported. The mechanism of the Tm³⁺-doped laser and the energy conversion loss is analyzed theorically. The slope efficiency of Tm:YLF laser calculated is 50%. In this experiment, fiber-coupled LD at 792 nm is used to pump the Tm:YLF crystal. The LD output is divided into two beams with the same power to the two double-end pumping crystal in a folded resonator. The Tm:YLF crystal with the dimension of 3 mm × 3 mm × 12 mm is doped with 4% Tm³⁺. The wavelength of the laser with different transmittances of output mirrors is measured. When the output mirror transmittance is 26%, the continuous wave output power of 20.1 W at 1.9 μm is obtained with 75 W pumping power, and the threshold is 9 W. At the same time, the slope efficiency of 34% and the optical-to-optical efficiency of 27% are achieved.