A high power laser system is provided having a master oscillator for
generating a reference laser beam of desired beam quality, means for
dividing the reference beam into multiple sub-beams, a multi-slab gain
module positioned to receive the multiple sub-beams as input beams, and
means for adjusting the sub-beams in phase to allow the output sub-beams
to be coherently combined as a single composite output beam. Optionally,
additional multi-slab gain modules similar to the first multi-slab gain
module may be positioned to receive amplified output sub-beams from the
first multi-slab gain module. The additional multi-slab gain modules
generate further amplified output sub-beams of high aggregate power.