Gain characteristics of an atmospheric sealed CW CO<inf>2</inf>laser

Experimental and analytical investigations have been made on unsaturated gain g0of a CO2electric-discharge convection laser, in which discharge current flow, gas flow, and the optical axis are mutually perpendicular. Stable glow discharges in sealed gas mixtures of CO2, CO, N2, and He were maintained at pressures up to 780 torr with an input power density of about 90 W/cm3. The ratio of electric field to neutral particle densityE/Nwas1.7 × 10⁻¹⁶V . cm2and was independent of the total gas pressureP. The electron density in a positive column of the glow discharge was about4 × 10¹⁰cm-3. Detailed spatial distributions of g0at a wavelength near 10.6 μm were measured in the pressure range from 100 to 780 torr. Measurements were also made on the current dependence of g0and on the change in gowith discharge time. The g0distributions along the gas flow direction were found to agree with those calculated from the electron density distribution and the relaxation rate constant of the upper laser level on the basis of continuity equations for a two-level model. The integrated value of g0along the flow direction was proportional to P-0.8whenE/N, electron density, and gas temperature were held constant. A maximum value of the g0distribution, which was proportional to P-0.3, was 0.14 percent/cm at 780 torr.