Triggering and guiding high-voltage discharge in air by single and multiple femtosecond filaments.

The abilities to trigger and guide high-voltage discharge by using single and <em>multiple filaments</em> (MFs) are experimentally studied. It is shown that the discharge voltage threshold can be reduced significantly in both regimes of single and MF; however, the MF does not gain a larger reduction than a single filament. This behavior of the MF is attributed to the single discharge path rather than simultaneous multiple ones as one might expect during the discharge process.