Mode and frequency control of compact CO_2 slab lasers through intracavity coherent imaging

The modal properties of a compact, slab-waveguide CO(2) laser are presented. Laser operation without mode selection is observed to be in groups of well-defined slab-waveguide modes that systematically change with mirror translation through a free spectral range and produce multiple homodyne beats. Single-mode operation, which is obtained through the addition of a wire-grid mode selector in combination with Talbot-effect imaging, is found to be stable over a significant range of resonator mirror tilt and optical cavity length translation. An output power of 65 W in a stable mode has been obtained from a compact laser head that is approximately 260 mm in overall length.