Resistance of dielectric-coated interference mirrors to laserinduced damage

Laser-induced damage in multilayer dielectric mirrors made from TiO₂ and SiO₂ was investigated for both single-pulse and pulse-periodic operation. The damage thresholds were measured and found to be lower in the pulse-periodic regime for mirrors having a low reflection coefficient at the laser wavelength. The thresholds of single-layer TiO₂ and multilayer TiO₂–SiO₂ coatings were governed by the damage resistance of the TiO₂ surface layers. The effect on the damage threshold of varying the radiation intensity at the boundaries of the TiO₂ layers was examined by shifting the spectral characteristics of a mirror relative to the laser wavelength.