Excimer emission from microhollow cathode discharges

Summary form only given. Microhollow cathode discharges (MHCDs) combine the possibility for direct current, high-pressure operation with non-equilibrium plasma conditions necessary for efficient excimer formation. When operated in rare gases (Xe, Ar, Ne) or rare gas halides (ArF, XeCl) these discharges were found to be intense sources of excimer radiation. Conversion efficiencies (from input electrical power to output optical power) of several percent were achieved. Although modeling results predict a monotonous increase of radiant power with pressure, in MHCDs it has a maximum at 400 Torr. The observed maximum of the radiant power at constant current was found to be due to the nonlinear reduction of the excimer source area with increasing pressure. The excimer source is located in the cathode opening only at high pressures and low currents. Otherwise, the source extends over the cathode surface outside of the hole. The emitting area decreases by a factor of four over the pressure range from 200 Torr to 760 Torr, whereas the radiant emittance increases monotonically with pressure up to 10 W/cm/sup 2/ at atmospheric pressure. For DC operation, the current was limited to 8 mA to avoid thermal damage.