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Branched flow of intense laser light in plasma with uneven density distribution

Branched flow is an interesting phenomenon that can occur in diverse systems. It is usually linear in the sense that the flow does not alter the medium properties. Branched flow of light on thin films was recently discovered. A question of interest is thus if nonlinear branched flow of light can also occur. Here we found using particle-in-cell simulations that with intense laser propagating in plasma with randomly uneven density distribution, photoionization by the laser can locally enhance the density variations along the laser paths and thus the branching of the laser. However, too-intense lasers can smooth the uneven electron density and suppress branching. The observed branching properties agree well with an analysis based on a Helmholtz equation for the laser electric field. Branched flow of intense laser in uneven plasma potentially opens up a new realm of intense laser-matter interaction.