Comparison Between Plasma Properties And Damage Thresholds In Doped Silica Exposed To IR Temtosecond Laser

Time resolved spectral interferometry shows that both the trapping time of electrons excited in the conduction band is strongly dependent on the doping nature (e.g. Ge, P or F) event for very low concentrations on the order of 1 at%. This is agreement with the birefringence threshold (T2) that exhibits a significant dependence on the used dopants. In contrast, we observed that the permanent isotropic index change threshold (T1) is not significantly dependent on the doping. This indicates that the T1 threshold is not determined by a "critical" excited electron density neither a self-trapped exciton density. Another criterion more appropriate for T1 would be the absorbed energy per pulse and its subsequent transfer to the glass network.