Comparative study of UV absorption changes induced in germanosilicate glass by high-intensity femtosecond pulses at 267, 400 and 800 nm

We investigated UV absorption changes induced in 3.5 mol% Ge-doped fused silica at high-intensity (∼1011–1013 W/cm2) femtosecond (130 fs) irradiation at 267, 400 and 800 nm. We have shown that the induced spectra in the region 190–300 nm are similar in all three cases. At 800 nm irradiation, in addition to the UV absorption changes, we observed small-scale damage due to self-focusing. This damage appears when the incident pulse fluence value of about 1 J/cm2 (pulse intensity of about 7.5 × 1012 W/cm2) is overcome, while the threshold for the induced absorption changes is twice lower.