Characterization of ultraviolet filaments in air

Summary form only given. Filaments have been the subject of much study in recent years. The general view is that self-focusing occurs in the laser beam until a higher order nonlinearity (usually believed to be multiphoton ionization) becomes significant. A balance then develops between these phenomena such that the beam remains confined to a small diameter over distances that greatly exceed the Rayleigh range. Such filaments have been well examined in the IR but not in the UV. To explore UV filaments, we use a hybrid Ti:sapphire/KrF system that provides 1.1 ps pulses of up to 100 mJ at 248 nm at 10 Hz.