Laser conditioning and multi-shot laser damage accumulation effects of HfO2/SiO2 antireflective coatings

Laser conditioning effects of the HfO2/SiO2 antireflective (AR) coatings at 1064 nm and the accumulation effects of multishot laser radiation were investigated. The HfO2/SiO2 AR coatings were prepared by E-beam evaporation (EBE). The singleshot and multi-shot laser induced damage threshold was detected following ISO standard 11254-1.2, and the laser conditioning was conducted by three-step raster scanning method. It was found that the single-shot LIDT and multi-shot LIDT was almost the same. The damage mostly > 80% occurred in the first shot under multi-shot laser radiation, and after that the damage occurring probability plummeted to < 5%. There was no obvious enhancement of the laser damage resistance for both the single-shot and multi-shot laser radiation of the AR coatings after laser conditioning. A Nomarski microscope was employed to map the damage morphology, and it found that the damage behavior is defect-initiated for both unconditioned and conditioned samples. © 2004 Elsevier B.V. All rights reserved.

Design and properties analysis of multi-layer dielectric used in pulse compressor gratings

Used in chirped-pulse amplification system and based on multi-layer thin film stack, pulse compressor gratings (PCG) are etched by ion-beam and holographic techniques. Diffraction efficiency and laser-induced damage threshold rely on the structural parameters of gratings. On the other hand, they depend greatly on the design of multi-layer. A theoretic design is given for dielectric multi-layer, which is exposed at 413.1 nm and used at 1053 nm. The influences of coating design on optical characters are described in detail. The analysis shows that a coating stack of H3L (H2L) (boolean AND) 9H0.5L2.01H meets the specifications of PCG well. And there is good agreement of transmission between experimental and the theoretic design. (c) 2005 Elsevier GmbH. All rights reserved.

Investigation of laser-induced damage on multi-layer dielectric gratings

We investigate mechanisms of laser induced damage thresholds (LIDTs) of multi-layer dielectric gratings (AIDG,). It is found that the laser damage thresholds of MDGs and unstructured dielectric multi-layer coatings (the substrate of MDG) are 3.15J/cm(2) and 9.32 J/cm(2), respectively, at 1064nm (12ns) with the Littrow angle 51.2 degrees and the TEM00 mode. The laser-induced damage mechanism of multi-layer dielectric is presented with the analysis of the following factors: The dominant factor is the pollution on the corrugated surface, which is induced by the complex manufacture process of multi-layer dielectric gratings; another is the electric field distribution along the corrugated surface. The third reason is due to the reduction in stoichiometry of oxide films, resulting from the manufacture process of etching.