213 nm Nd-YAG pulsed laser damage of non-loaded and hydrogen-loaded silica-based fibers

An automated set-up for 213 nm UV laser damaging in parallel to spectral analyses will be used to show the spectral laser damaging in silica-based fibers with low hydroxyl content. The 213 nm wavelength is ideal, because it is close to the peak wavelength of one of the E’-centers in silica. Due to automation, short-term measurements down to 0.5 s and long-term measurements up to 2 days and more are possible. In addition, the spectral transmission changes are fitted with multiple Gaussian shaped bands. Although the basic attenuation in non-loaded fibers is high, the pulse energies are still high enough to generate defects along a 1 m long fiber. For the first time, to our knowledge, a transfer from E’γ to E’γ is observed within 1 s, with a laser repetition rate of 2 kHz. Due to optimal fitting, a band around 180 nm is likely influencing the UVC region. In hydrogen-loaded fibers, similar UV defects are seen. The related absorption bands can be optimally adopted to measurement results. The E’-centers play a minor role in short-term measurements because these defects are passivated during hydrogen-loading. Additionally, the band at 328 nm due to molecular chlorine will be reduced. The temporal behavior of all absorption band, including the predicted 180 nm band, are shown.