We demonstrate a 2.09 μm Ho:YAG pulse power amplifier featuring high power, high efficiency, and low depolarization loss. By optimizing the gain medium structure, the maximum average output power of Ho:YAG amplifier was increased from 432 to 446 W with a seed power of 250 W. Wherein, the linearly polarized power was improved from 397 to 420 W, along with a decrease in depolarization loss from 0.082 to 0.058. At the maximum output power, the beam quality M2 factor was better than two times diffraction limited. The pulsewidth was ~ 50 ns at the pulse frequency repetition of 40 kHz. Furthermore, using the Ho:YAG laser as a pump source for a ZnGeP2 signal singly resonant optical parametric oscillator, the maximum output power was scaled to 151 W at the wavelength of 3.86 and 4.55 μm. [ABSTRACT FROM AUTHOR]