Dual-wavelength collaboratively pumping scheme for a 3.9  µm continuous-wave Ho:YLF laser

A dual-wavelength collaboratively pumping scheme is proposed to realize the efficient operation of a 3.9 µm continuous wave Ho:YLF laser. An 888 nm laser is used to excite ions from the 5 I 8 ground-state manifold to the 5 I 5 laser’s upper manifold. Another 2.1 µm laser is used to excite ions from the 5 I 6 laser’s lower manifold to the short-lived 5 I 4 manifold to eliminate the self-terminated effect of 3.9 µm laser oscillation. Numerical simulation of 3.9 µm laser output performances is carried out, based on the developed rate equations. Simulation results indicate that the dual-wavelength collaboratively pumping scheme is feasible to realize the highly efficient output of the 3.9 µm continuous wave Ho:YLF laser. The relationship between the pump power for 888 nm and 2.1 µm laser sources is analyzed to obtain the optimal output. Furthermore, the impacts of crystal doping concentration, crystal length, output mirror transmittance, and important energy-transfer processes on the laser output performances are also analyzed. The dual-wavelength collaboratively pumping scheme provides beneficial guidance for the generation of a 3.9 µm high-power continuous-wave laser in an Ho:YLF laser.