Revival of femtosecond laser plasma filaments in air by a nanosecond laser

Bing Zhou,Michel Franco,Selcuk Akturk,Aurélien Houard,Estelle Salmon,Ciro D’Amico,André Mysyrowicz,Zuo-Qiang Hao,Yi Liu,Yves-Bernard André,Noelle Lascoux,Bernard Prade

doi:10.1364/oe.17.011450

Abstract

Short lived plasma channels generated through filamentation of femtosecond laser pulses in air can be revived after several milliseconds by a delayed nanosecond pulse. Electrons initially ionized from oxygen molecules and subsequently captured by neutral oxygen molecules provide the long-lived reservoir of low affinity allowing this process. A Bessel-like nanosecond-duration laser beam can easily detach these weakly bound electrons and multiply them in an avalanche process. We have experimentally demonstrated such revivals over a channel length of 50 cm by focusing the nanosecond laser with an axicon.

Highlights

Much attention has been given in the last few years to the propagation of ultrashort laser pulses in air
Short lived plasma channels generated through filamentation of femtosecond laser pulses in air can be revived after several milliseconds by a delayed nanosecond pulse
We have experimentally demonstrated such revivals over a channel length of 50 cm by focusing the nanosecond laser with an axicon

Summary

Introduction

Much attention has been given in the last few years to the propagation of ultrashort laser pulses in air. A dielectric medium such as air is readily driven into a highly nonlinear regime Several groups have reported the occurrence of femtosecond (fs) filamentation (for recent reviews see [1,2,3]) In this process, an intense ultrashort laser pulse self-organizes into a contracted beam, 10-100 μm in diameter, fed by a surrounding laser energy reservoir. The contracted beam, often called filament, carries a peak intensity of I ~ 5x1013 W/cm sufficient to ionize air molecules in a multiphoton process It maintains this high intensity over distances which can reach several hundreds of meters in air because of the dynamic balance between self focusing (due to the optical Kerr effect) and beam defocusing (due to multiphoton ionization of air molecules) [1,2,3]

Methods

Results

Conclusion