Based on the steady heat conduction equation, LD double-end-pumped anisotropic Tm:YLF crystal temperature field analytical expression and thermal focal length are obtained by the integral-transform method. The influence of pump conditions and crystal parameters on the distribution of temperature and thermal focal length are quantitatively analyzed. The simulation results showed that increasing the pump power, decreasing waist radius, increasing doping concentration or decreasing crystal length, the temperature rise of crystal and nonuniformity of the thermal distortion are intensified, the corresponding thermal effects enhance, the thermal focal length gets shorter. The anisotropic of the physical and optical parameter of Tm:YLF crystal leads to the anisotropic of thermal effect. When the product of crystal length and doping concentration is a constant value, the thermal focal length keeps a basic consistent.

A narrow linewidth cw Ho:YAG laser pumped by a 1908 nm Tm:YLF laser based on the volume Bragg grating is established. The maximum output power of 9.6 W for the incident pump power of 16.9 W is obtained, and the corresponding slope efficiency and optical-to-optical conversion efficiency are 67.2% and 56.8%, respectively. The Ho:YAG laser operates stably at 2122.1 nm by using two Fabry-Perot etalons, with a full width at half maximum less than 0.2 nm.

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