Microarcs as a termination mechanism of optical pulses in electric-discharge-excited KrF excimer lasers

A theoretical investigation is conducted of both macroscopic (⩽mm´s to cm´s) and microscopic (<100´s μm) nonuniformities in electric field, preionization density, and halogen density as precursors to arcs and microarcs in KrF lasers. Macroscopic nonuniformities lead to volumetric arcing. Microscopic nonuniformities lead to filamentary arcs and streamers. It is found that microarcs may terminate the optical pulse due to disruption of the optical homogeneity of the plasma prior to the collapse of impedance of the discharge. Small-scale microscopic inhomogeneities (<10´s-100 μm) develop into microarcs sooner than large-scale homogeneities (>10´s-100 μm) due to the higher pressure gradient afforded by their small size. Large-scale inhomogeneities, though, are ultimately more detrimental to the performance of the laser