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 cooling of the discharge column, which corresponds to the maximum emitted intensity. Optogalvanic coupling between emitted intensity and local discharge impedance values yields a transverse redistribution of discharge current and, hence, of laser gain. Thus, besides the fast feedback provided by the cavity, with high-power lasers one must account also for a slow global feedback because of the optogalvanic effects.