Surface discharge-pumped XeF (C→A) laser

Surface discharge-pumped XeF (C→A) lasers producing single pulse energies as large as approx.140 J have been reported previously. Having active lengths as large as 1.8 m, these devices produced pulses with temporal widths of typically 2-3 μs but operated on essentially a single shot basis. We have designed and tested a surface discharge-pumped XeF laser based on a new design for the entire electrical system. Previous, sectioned-discharge devices employed inter-electrode spacings of 11 cm and each section was switched independently. The current design has an active length of 48 cm and operation at 30 kV is possible because of installation of capacitively-ballasted molybdenum pins installed in the surface dielectric. This design avoids the need for external switches and results in a low inductance electrical discharge system that operates near the critically damped regime, thus maximizing power deposition in the active medium and minimizing stress on electrical components. All of these characteristics lead to a device that is capable of repetitive operation and is rugged and reliable. Laser experiments have been carried out to date on the B→X and C→A bands of the XeF molecule. Typically, the gas mixtures are composed of 850 Torr Ar, 200 torr N, 2-3 torr XeF₂, and 10 torr SF₆ in which the latter serves to remove low energy electrons by dissociative attachment, thereby further stabilizing triggering of the discharge. The XeF₂ number density is monitored in real time by optical absorption at 254 nm. Measurements of the small signal gain on the C→A band have also been made at 488 nm with an Ar⁺ laser and the result - 0.3%-cm^-1, is virtually identical to values obtained previously by Zuev, Mamaev and coworkers. Although this device is designed to be operated at pulse repetition frequencies as high as several hertz, tests have been conducted only in a single shot mode. Further details regarding the design and performance of this laser, including the optimization of output power with respect to cavity coupling, will be discussed.