Damage threshold measurements. Self-focusing or intrinsic damage?

摘要

The laser-induced damage (LID) thresholds of pure fused silica (Corning 7980) have been measured with single temporal mode nanosecond pulses at 1064 nm. The laser beam has been focused by spherical and conical lenses into 1.6 μm diameter spots. In the case of pseudo-Bessel beam (conical lens) which inherently was not subjected to self-focusing the threshold has been close to the intrinsic threshold in fused silica. However, the measurement with pseudo-Gaussian beam (spherical lens) has shown about 30％ lower value of threshold. Complete identity in the cross-section distributions of beam intensities and considerable difference in measured thresholds indicate that self-focusing influence on the LID of dielectrics even for tight focused laser beams.