Changes in the bulk damage threshold of optical glasses as a result of repeated irradiation with laser pulses

Experiments demonstrated that interaction of laser radiation of subthreshold intensity and nanosecond duration with optical glasses free of absorbing microinhomogeneities (K8, KU1, LK6, etc.) induced residual changes in the optical properties, which reduced the bulk damage threshold for the subsequent (repeated) action of laser pulses. Residual changes in the nonlinear refractive index induced by subthreshold radiation of wavelengths 0.53 and 1.06 μm (i.e., under conditions such that hv < E_g / 2, where E_g is the ionization potential of the glass matrix) were observed for the first time.