Recent advances in pulsed HF/DF lasers

Recently, some noticeable effort as been realized in order to improve characteristics of HF/DF pulsed lasers. A few years ago it was supposed that the realization of a high energy HF/DF pulsed laser was only possible by using E-beam excitation, either for a non chain HF/DF gas mixture, or for a chain reaction mixture i.e. H-2/F-2 mixture. Flash lamp initiation of a high-energy chain reaction HF/DF laser was also demonstrated. However every one who wanted to make such a laser working repetitively was convinced of the difficulty of operating an E-beam. system or high energy flash lamps repetitively, even at moderate repetition fate. Discharge excitation was supposed to be very difficult to be used for large volume due to the strong electronegative character of the used gases. First attempts to realize large volume discharges have shown that this last idea was not true and that it was relatively easy to obtain homogeneous discharges in SF6 based mixture when the hydrogen donor was a hydrocarbon such as C-2-H-4 or C-6-H-12. This paper will present recent developments directed towards a better understanding of the discharge mechanisms and to an increase of the efficiency and of the specific output energy of HF/DF pulsed lasers by using chain reaction in discharge initiated repetitive and non-repetitive experiments.