Experimental and theoretical studies of subpicosecond laser damage in TixSi1-xO2 composite films

The scaling law of subpicosecond laser induced damage (LID) with respect to pulse duration and band gap for TixSi1-xO2 composite films is studied. The band gap in these materials can be changed gradually by varying the composition pa-rameter x. Damage is very deterministic and scaling laws with respect to pulse duration and band gap energy derived previously for pure materials are found to apply to composite films. The scaling can be explained theoretically by using a modified Keldysh theory. The composite materials also show a dependence of the damage threshold as a function of pulse number F(N) (incubation) that is similar to observations in pure dielectric oxides. The measured F(N) is explained with a theoretical model that assumes the formation of an intermediate sample state that increases the absorption of sub-sequent pulses in the train.