Sealed excimer laser with longitudinal discharge and transverse

Abstract

The gas enclosure of this laser includes a reservoir but no gas exhaust port--or valve leading to such a port or to ambient. Preferably the enclosure is sealed by an essentially permanent-type seal such as a glassblown seal, and connects with no pump, or valve leading to a pump. System life, in intermittent use or low-repetition-rate continuous use, is over a year without gas replenishment. Opposed metal coatings on the exterior of a discharge capillary tube form preionization electrodes, each extending nearly the entire capillary-tube length. These electrodes are energized to establish a transverse discharge inside the capillary tube, with good uniformity of initial ion density along the capillary tube. The electrodes couple to this discharge capacitively, through the capillary-tube wall, thereby isolating electrode materials against chemical reaction with corrosive gases in the system. Voltage applied longitudinally to internal electrodes, in chambers at the ends of the capillary, establishes the main discharge in this preformed ion population. Ionization uniformity permits lasing action to develop in good synchronism throughout the capillary-tube length, overcoming rapid self-quenching of the excimer to develop a laser pulse from nearly the entire capillary-tube volume.