Theoretical study of a vacuum ultraviolet F₂ excimer lamp (157 nm) excited by microwave discharge

A high-efficiency operation of a vacuum ultraviolet (VUV) incoherent light source of a F₂ excimer lamp [157 nm:F₂(D')-F ₂(A')] excited by a pulsed microwave discharge has theoretically been studied. Despite the low-pressure (300 Torr) operation, an intrinsic efficiency of 10.6% and a F₂(D') formation efficiency of 17.4% were found to be obtainable at an optimum F₂ concentration (0.5%) using He/F ₂ mixtures. The F₂(D') state is mainly produced by energy transfer reaction from F*. Using a 300 Torr mixture of He/F ₂=99.5/0.5(%), a photon extraction efficiency of 60.9% is achievable with a low energy loss (39.1%) by collisional quenching. The corresponding optical output of 50.0 μJ/cm³ is achievable at an excitation rate of 100 W/cm³ and an excitation pulse width of 9.0 μs. Since it can be operated at high repetition frequency of up to 55 kHz using conventional devices, an average output power of 2.75 W/cm³ is achievable.