In this paper we discuss a CW Yb:YAG cryogenic laser program that has resulted in the
design and demonstration of a novel high power laser. Cryogenically-cooled crystalline
solid-state lasers, and Yb:YAG lasers in particular, are attractive sources of scalable CW
output power with very high wallplug efficiency and excellent beam-quality that is
independent of the output power. This laser consists of a distributed array of seven
highly-doped thin Yb:YAG-sapphire disks in a folded multiple-Z resonator. Individual
disks are pumped from opposite sides using fiber-coupled ~ 30W 940nm pump diodes.
The laser system we have constructed produces a near-diffraction-limited TEM00 output
beam with the aid of an active conduction-cooling design. In addition, the device can be
scaled to very high average power in a MOPA configuration, by increasing the number
and diameter of the thin disks, and by increasing the power of the pump diodes with only
minor modifications to the current design. The thermal and optical benefits of
cryogenically-cooled solid-state lasers will be reviewed, scalability of our Yb:YAG
cryogenic laser design will be discussed, and we will present experimental results including output power, slope and optical-optical efficiencies, and beam-quality.