We present our recent developments in high-power, high-efficiency cryogenic Yb:YAG laser systems. Specifically, we
will discuss our 2.3-kW master oscillator power amplifier (MOPA) which has shown optical wall-plug efficiencies
above 30-% (diode-driver input to optical output). This laser system has been operated for long run times with
continuous wave and pulsed output formats. The beam quality factor, M2, of the MOPA has been measured to be less
than 2 and it is currently limited by the master oscillator. We are working to improve the device's beam quality and
output power. In addition, we have demonstrated an all-cryogenic Yb:YAG laser that produced 29 W of optical power.
Use of cryogenic diode laser pumps represents our next step towards achieving greater than 50% efficient high-power