Accumulation and Laser Damage in Optical Glasses

Bulk damage of the optical glasses by single and multiple periodic laser pulses of nanosecond duration has been investigated. In the case of multiple irradiation, damage is shown to occur with the energies considerably lower than the damage threshold by a single pulse. The dependence of the accumulating damage threshold on the number and frequency of the irradiation pulses, the wavelength of laser radiation and the conditions of its focussing into the volume of the sample has been observed. The bulk damage of glass K-8 induced by a single pulse of radiation with 1.06 μm and 0.53 μm wavelength is shown to be determined by different mechanisms. By employing absorptive-spectral analysis, the degradation of the medium under laser irradiation with intensity ten times lower than damage threshold was observed. The mechanisms of the accumulation and bulk damage are also discussed.