The effect of light-induced plasma on propagation of intense fs laser radiation in c-Si

The strong two-photon absorption and induced plasma are well-known factors restricting the penetration of intense focused laser pulses in silicon crystals. In this paper, we demonstrate that the role of plasma is not exhausted by the defocusing effect in a beam waist. We investigated experimentally the propagation of an IR laser pulse focused inside a silicon target and found a complex filament-like transformation of the beam. The results of numerical simulation suggest that this behavior is the result of wavefront distortion induced by the subsurface plasma ρ s .