An analytical approach to the design of electrodes in high-power, fast-transverse-flow CO2 lasers

Usually, the design of the electrodes of fast-transverse-flow CO2 lasers relies more on experimental data than on theoretical analysis. Traditional systems sustain a stable, high-power discharge but the current distribution generates a peaked, non-uniform small-signal-gain pattern. We present a theoretical model suitable for the design of electrodes that achieves a quasi uniform gain distribution. The analysis, based on a two-temperature model and the gas-transport equations, computes the electron density that supports a flat gain pattern. Combining the desired electron density with the electron-balance equations, the model determines the required electric field. The results were used to design a new set of electrodes for a home-made fast transverse flow CO2 laser. A stable, large volume discharge (4×8×90cm3) with very good uniformity was obtained. The resulting gain distribution was registered in a bi-dimensional map. The peak gain rose from 1.2m-1, attained with the old electrode set, to 1.6m-1 with the new one and the gain showed a homogeneous profile.