PATTERN COMPETITION IN A HIGH-POWER CO2-LASER DUE TO OPTOGALVANIC MODULATION OF THE PUMP PROFILE

Experimental evidence of periodic alternation of different transverse modes in a high-power CO, laser is interpreted in terms of local cooli ng of the discharge column, which corresponds to the maximum emitted i ntensity. Optogalvanic coupling between emitted intensity and local di scharge impedance values yields a transverse redistribution of dischar ge current and, hence, of laser gain. Thus, besides the fast feedback provided by the cavity, with high-power lasers one must account also f or a slow global feedback because of the optogalvanic effects.