Excimer KrF laser with He buffer gas, 0.8 J energy, and 2% efficiency

An experimental investigation was made of the energy and temporal characteristics of the pump process and of the output radiation of a pulsed gas-discharge excimer KrF laser (λ = 248 nm) with He as the buffer gas. An RU-65 spark gap was used as the design base. The parameters of a high-voltage excitation circuit of the LC inverter type with automatic UV preionisation were optimised. A laser efficiency (based on the stored energy) of 2.4% and an output radiation energy of 0.57 J were reached for the first time for a gaseous medium of the He:Kr:F₂ = 89.8:10:0.2 composition at a total pressure of 2.5 bar. The maximum output energy of the KrF laser was 0.82 J in the form of pulses of 24 ns duration at half-amplitude; the specific output energy was then 5.9 J litre^–1 and the efficiency was 2.0%.