Filamentation and damage in fused silica induced by tightly focused femtosecond laser pulses

Abstract : We investigate experimentally and numerically the damage tracks induced by tightly focused (NA=0.5) infrared femtosecond laser pulses in the bulk of a fused silica sample. Two types of irreversible damage are observed. The first damage corresponds to a permanent change of refractive index without structural modifications (type I). It appears for input pulse energies beyond 0.1 μJ. It takes the form of a narrow track extending over more than 100 μm at higher input powers. It is attributed to a change of the polarizability of the medium, following a filamentary propagation which generates an electron-hole plasma through optical field ionization. A second type of damage occurs for input pulse energies beyond 0.3 μJ (type II). It takes the form of a pear-shaped structural damage associated with an electron-ion plasma triggered by avalanche. The temporal evolution of plasma absorption is studied by pump-probe experiments. For type I damage, a fast electron-hole recombination is observed. Type II damage is linked with a longer absorption.
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Submitted on : Saturday, March 13, 2010 - 1:11:51 AM
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Arnaud Couairon, Lionel Sudrie, Michel Franco, Bernard Prade, André Mysyrowicz. Filamentation and damage in fused silica induced by tightly focused femtosecond laser pulses. Physical Review B : Condensed matter and materials physics, American Physical Society, 2005, 71 (12), pp.125435. ⟨10.1103/PhysRevB.71.125435⟩. ⟨hal-00463614⟩

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