MICROFILAMENTATION IN OPTICAL-FIELD-INDUCED IONIZATION PROCESS

A plasma-resonance field-ionization instability of uniform gas breakdo wn produced by intense laser fields via tunneling ionization of atoms is studied theoretically and by computer simulation. The field amplitu de and produced plasma are found to be unstable relative to spatial mo dulation in the direction of electric field with the spatial period sh orter than the wavelength. In a dense gas the process, at the nonlinea r stage of instability, becomes explosive and leads to the formation o f thin resonance layers and sharp peaks of the field amplitude.