A system includes a master oscillator configured to generate a low-power optical beam. The system also includes a planar waveguide (PWG) amplifier configured to receive the low-power optical beam and generate a high-power optical beam having a power of at least about ten kilowatts. The PWG amplifier includes a single laser gain medium configured to generate the high-power optical beam. The single laser gain medium can reside within a single amplifier beamline of the system. The master oscillator and the PWG amplifier can be coupled to an optical bench assembly, and the optical bench assembly can include optics configured to route the low-power optical beam to the PWG amplifier and to route the high-power optical beam from the PWG amplifier. The PWG amplifier could include a cartridge that contains the single laser gain medium and a pumphead housing that retains the cartridge.