Influence of local micro-inhomogeneity of refractive index on laser-induced damage of wide band-gap dielectrics

There is effect of nonlinear light propagation through dielectric with small non-absorbing micro inclusion that can play important role in initiating of laser-induced damage of transparent materials. The effect is developing of field instability in non-absorbing micro inclusions. It is shown that transparent micro inclusion can initiate local field increase accompanied by positive feedback resulting in further field increasing near the inclusion. If the electric field strength exceeds damage threshold during nonlinear evolution in the inclusion then developing of field instability results in damage of micro-inclusion before electric field reaches certain upper level determined by ionization processes. There is estimated threshold of field instability. Its dependence on material and radiation parameters is studied.