LATERAL AND TRANSVERSE-MODE PROPERTIES OF CO2 SLAB WAVE-GUIDE LASERS

The output of a high Fresnel number, slab waveguide, carbon dioxide laser has been investigated for electrode gaps between 0.7 and 2.25 mm. The observed beam intensity patterns are found to be consistent with analysis in terms of high order rectangular waveguide modes. High order transverse mode suppression for gaps less than 1.5 mm has been attained and the lateral mode signature understood in terms of waveguide mode frequencies and spatial mode competition. Operation in a single EH16,1 waveguide mode has been demonstrated. Output power for an 18 mm wide slab has been increased to 210 W at 1 mm electrode gap, corresponding to a specific power of 30 kW m-2 for planar, large electrode area, rf excited lasers. The cross-over between the effects of the (gap)-1 discharge scaling law and the (gap)-3 scaling of guide loss is shown to occur at approximately 1.2 mm for aluminum electrodes.