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

Abstract

Experimental and analytical investigations have been made on unsaturated gain g 0 of a CO 2 electric-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 CO 2 , CO, N 2 , 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 density E/N was 1.7 \times 10^{-16} V . cm2and was independent of the total gas pressure P . The electron density in a positive column of the glow discharge was about 4 \times 10^{10} cm-3. Detailed spatial distributions of g 0 at 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 g 0 and on the change in g o with discharge time. The g 0 distributions 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 g 0 along the flow direction was proportional to P-0.8when E/N , electron density, and gas temperature were held constant. A maximum value of the g 0 distribution, which was proportional to P-0.3, was 0.14 percent/cm at 780 torr.