Abstract

A femtosecond UV pulse is an effective source of photoelectrons through multiphoton ionization in gases, thanks to the high peak power of the short pulse. When such a pulse is sent through an intense (but smaller than the avalanche breakdown field E_a) electric field, our simulation shows that the photoelectrons drift and multiply. Inside the column of charges, the field is reduced by a local field resulting from a partial charge separation. However, as the electrons drift towards the anode, within a few microsecond a dramatic local field enhancement develops at the edge of the column (Fig. 1). When the peak local field reaches the value E_a, an avalanche breakdown occurs, leading to a lightning discharge. ^1,2

© 1994 Optical Society of America