Abstract

Laser-generated plasmas in air have potential utility in diverse application areas ranging from the guidance of electrical discharges to remote sensing. Ionization of air and other gases by powerful laser pulses has been intensely investigated in the femtosecond [1,2] and nanosecond [3] regimes. However, plasma channels produced through fs excitation are dilute and short-lived, while plasmas generated through nanosecond optical breakdown are typically fragmented into disconnected plasma bubbles. Both shortcomings severely limit practical applications. Attempts to combine femtosecond and nanosecond laser excitations in the so-called igniter-heater scheme [4] do result in the production of extended and dense plasma channels, but, like in the case of pure nanosecond excitation, the generated plasma channels are fragmented into discrete bubbles, as shown in Figure 1. The fragmentation effect is attributed to the periodic focusing of the nanosecond heater pulse by the rotational revivals impulsively initiated by the femtosecond igniter pulse.

© 2015 Optical Society of America