Numerical simulations of induced spatial incoherence laser light self-focusing

Abstract

The effect of induced spatial incoherence (ISI) on laser light self-focusing is investigated using a two-dimensional Eulerian hydrodynamic plasma simulation code. In homogeneous low-density plasmas (one-tenth of the critical density for radiation of wavelength λL=0.25 μm) it is found that ISI can effectively eliminate thermal and ponderomotive self-focusing for a wide range of intensities. In plasma containing an initial linear gradient in density, strong self-focusing occurs when the maximum intensity in the incident light I0 (where I0 represents the intensity that would be achieved for a perfectly coherent beam) is allowed to approach 1017 W cm−2. At lower intensities, I0∼1016 W cm−2, thermal self-focusing is eliminated and ponderomotive self-focusing is significantly reduced. The dwell time of the filamented light varies from the laser light coherence time to a few tens of picoseconds.