The mechanism of laser-induced damage in transparent materials, caused by thermal explosion of absorbing inhomogeneities

A mechanism is proposed for macroscopic damage to transparent dielectrics, resulting from the explosion of small-diameter ($\lesssim10^{-5}$ cm) absorbing inhomogeneities. The mechanism given is caused by ultraviolet preionization of the matrix surrounding the inhomogeneity and by the appearance in it of free carriers inducing additional absorption. This absorption results in the explosion of the ionized region and thus in the propagation of a discharge. The importance is indicated of induced absorption in a growing crack, caused by charge separation on its walls (the triboelectric process).