Vacuum ultraviolet argon excimer production by use of an ultrashort-pulse high-intensity laser

We report on the observation of Ar₂^* emission at 126 nm by use of a hollow fiber to guide the high-intensity laser propagation in high-pressure Ar. A small-signal gain coefficient of 0.05 cm^-1 was measured at 126 nm by this method. The increase of the Ar₂^* emission intensity was measured to be exp(2.5), with an increase of the fiber length up to 50 cm. Kinetic analysis revealed that the Ar₂^* production processes were initiated by the electrons produced by the high-intensity laser through an optical-field-induced ionization (OFI) process. A rapid conductive cooling of the OFI electrons is favorable to initiate the Ar₂^* formation kinetics more efficiently. This high-density cold plasma production method should be applicable for other vacuum ultraviolet rare-gas excimer lasers.