Laser filament creates long-lived conducting ‘wire’ in air

Using the Teramobile Ti:sapphire mobile chirped-pulse-amplification femtosecond laser (see www.laserfocusworld.com/articles/221432), French researchers at the Ecole Polytechnique (Palaiseau), CNRS (Villeurbanne), and SNCF (Vitry-sur-Seine) have created plasma filaments that pass between two electrodes and form permanent current-conducting columns in air (permanent at least until the electrodes melt, which happens after about a second).The columns have an electrical resistance low enough for potential practical uses in the contactless capture of current, for example, in testing the motors of high-speed trains.

Pulses of 100 fs duration, a peak power of several terawatts, and a repetition rate of 10 Hz were focused by a telescope so that they passed through one electrode and struck a second electrode 3 to 60 mm away. A 3 kV, 250 A direct current was carried over the column with an ohmic resistance of less than 0.1 Ω/cm, while a 50 Hz alternating current with 20 kV peak voltage was carried with a resistance of 25 Ω/cm. The initial cold laser-created plasma was converted by the current to a long-lived plasma with a temperature of about 35,000 K. Contact Andre Mysyrowicz at [email protected].