Q-switched operation of a diode-side-pumped, conduction-cooled Tm,Ho:YLF laser oscillator with 100-mJ output at a pulse repetition rate of 20 Hz and an eye-safe wavelength of 2-mu m was achieved. The noncomposite Tm, Ho: YLF laser rod was conduction-cooled down to -80 degrees C through thermal contact of In films from Cu heat sinks, and the laser diode arrays were conduction-cooled to approximately 20 degrees C using Cu heat sinks in a vacuum container. A ring resonator of 3.86 m length with an acousto-optic Q-switch was used. The pulse width was 125 ns, and optical-to-optical efficiency was approximately 7% for an output of 100 mJ. The laser is used at 2.05 mu m for applications of Doppler wind lidar measurements, CO2 differential absorption lidar measurements, and aerosol profiling. (C) 2015 Optical Society of America