Large-bore copper-vapor lasers: Kinetics and scaling issues

The scaling characteristics of large diameter (6≤d≤12 cm) high repetition-rate copper-vapor lasers are investigated using a radially dependent laser-discharge model. Results of the model are verified with experimental data obtained on several devices including an 8-cm-diam 100-W copper-vapor laser. Two effects, penetration of the applied electric field into the plasma and gas heating, which we show are the primary considerations in volumetric scaling, are discussed in detail. Thermal constriction of the discharge resulting from gas heating is prevented by plasma skin effects that allow stable performance at large diameters. These same effects are shown to explain the sequential excitation of the laser levels, resulting in both temporally and spatially dependent behavior of the laser pulse. Projections of output power and light-pulse characteristics are made for lasers up to 12 cm in diameter.