The effect of laser radiation on the laser damage resistance of dielectric coatings

The effect of pulses of laser radiation at a wavelength λ = 1315 nm with durations in the range 0.5–0.7 ns on the laser damage resistance of high-reflection, antireflection, and polarizing coatings and quarter-wave plates made from SiO₂ is measured and discussed. The study includes various impact geometries and radiation polarizations. It is shown that for high-reflection coatings the damage resistance depends strongly on whether the coating is at the entrance or exit surface, whereas for antireflection and single-layer coatings there is essentially no such dependence. The threshold for destruction of polarizing coatings depends on the polarization of the radiation. These results are explained within the framework of a mechanism according to which the microscopic absorbing inhomogeneities which initiate the destruction are concentrated predominantly at the boundary between the coating and substrate.