KRF-LASER IRRADIATION INDUCED DEFECTS IN ALL SILICA OPTICAL FIBERS

High power UV laser irradiation of synthetic fused silica material induces transient absorption bands centered at 215 and 265 nm. The temporal behaviour of the 215 and the 265 n-m- absorption bands and also of the 248 nm laser transmission were measured with a transient absorption spectrometer during KrF excimer laser irradiation. Fiber samples made from stoichiometric and non-stoichiometric fused silica core material were irradiated at room temperature. The absorption at 215 nm correlates with the laser absorption in stoichiometric materials, whereas in the sample with oxygen rich core material a linear correlation is observed for 265 and 248 nm. The experimental data give evidence that the laser induced decrease in transmission at the laser wavelength can be reduced by using stoichiometric material.