Fluoride crystal-based direct AlGaAs diode-pumped 2.1um laser

We present a compact diode-pumped Tm/Ho:YLF laser, via integrating the Tm-doped and Ho-doped YLF crystals into a single bulk gain medium. Gain spectral model was developed first to the predict the potential Tm:YLF laser wavelength using different types of output coupling, for enhancing resonant absorption of the Ho:YLF crystal. Further verification were carried out by intra-cavity pumping the Ho:YLF laser with a Tm:YLF laser, where maximum output power of 11.3 W at 2.06 μm with near diffraction limited beam quality was obtained with conversion efficiency of 28.2% by considering the incident 793 nm diode power. In the Tm/Ho:YLF laser, maximum output power of 10.2 W at 2063 nm with power instability of 0.55% was obtained, corresponding to a slope efficiency of 29.6 % and optical conversion efficiency of 25.5%. The results provide a compact, accessible, and efficient Ho laser scheme, with has potential applications in wind lidar, surgeries, material processing, and nonlinear frequency conversion toward the mid-infrared region.