Power scaling in slab waveguide CO₂ lasers

Measurements of laser characteristics were made relative to the performance of an optimum-design, square-cross-section waveguide channel of 2.25- × 2.25- × 376-mm³ dimensions. This single channel emits 32 W (85 W/m) when excited at 125 MHz using a 3:1:1 He:N₂:CO₂ mixture augmented by the additional of 5% xenon. The ceramic sidewalls were progressively separaped by multiples of 2.25 mm to create a sequence of slab widths corresponding to between one and eight equivalent waveguide channels. For eight channels a power of 036 W, corresponding to a 17-W/equivalent channel or 53% that of a single channel, was observed. As the slab width increased, the optimum pressure decreased from 110 to 75 torr and the efficiency increased somewhat. The smooth transition of optimum conditions from two to five channels reflects the changeover from 2-D to 1-D heat flow and diffusion. At eight channels this transition is complete, and the power is proportional to an increasing electrode area. These results show that the power can be scaled as 20 kW/m² of discharge area for large aspect ratios under conditions suitable for sealed-off operation.