Self‐guiding of high‐intensity laser pulses for laser wake field acceleration

Abstract

A means of self‐guiding an ultrashort and high‐intensity laser pulse is demonstrated both experimentally and numerically. Its relevance to the laser wake field accelerator concept is discussed. Self‐focusing and multiple foci formation are observed when a high peak power (P≳100 GW), 1 μm, subpicosecond laser is focused onto various gases (air or hydrogen). It appears to result from the combined effects of self‐focusing by the gas, and de‐focusing both by diffraction and the plasma formed in the central high‐intensity region. Quasi‐stationary computer simulations show the same multiple foci behavior as the experiments. The results suggest much larger nonlinear electronic susceptibilities of a gas near or undergoing ionization in the high field of the laser pulse. Although self‐guiding of a laser beam by this mechanism appears to significantly extend its high‐intensity focal region, small‐scale self‐focusing due to beam non‐uniformity is currently a limitation.