In this article ,we use finite element method to simulate the process of multi-pulse laser irradiate on fused silica.
Simulation results show that:during laser pulse radiation, the temperature rise of the laser-radiating fused silica surface
center point is nearly linear. During the pulse interval without pulse acting, due to none of thermal source or energy
concentration and the fused silica being at cooling phase, the temperature of the laser-radiating fused silica surface center
point declines sharply. At the fused silica surface where r=0.6mm, hoop stress turns to be tensile stress. When the next
pulse starts to act, the stress increases rapidly once again the maximum value of it is higher than the former one. Thus,
we can judge that the laser accumulation acts a major role in increasing tensile stress effect.
Meanwhile, we can figure out that the stress increase rate generated by the pulse laser of duty ratio 1:10 is higher than
the one of duty ratio 1:20 during the whole procedure. Along with shorter intervals of every two neighbor laser pulses of
duty ratio 1:10, the regression time of the tensile stress is comparably shorter. Thus, during the whole laser radiation
procedure, the initial tensile stress of every pulse of duty ratio 1:10 is greater than the one of duty ratio 1:20. Hence we
obtain the conclusion that, it’s much easier to generate damage when the pulse numbers in unit time increase with other
parameters of the laser do not change.