Techniques for fabrication of multilayer dielectric graded-reflectivity mirrors and their use enhancement of the brightness of the radiation from a multimode Nd3+:YAG laser with a stable cavity

Techniques for fabrication of multilayer dielectric mirrors with the reflectivity varying over their surfaces are described. They were used at the output of the cavity of a high-power industrial Nd³⁺:YAG laser to form a beam with a Gaussian or super-Gaussian intensity distribution. The permissible range of variation of the mirror reflectivity was 40 — 90% and it was reproducible from sample to sample to within 5%. A mirror with the reflectivity of 84% was used at the output of a plane – plane cavity of a cw Nd³⁺:YAG laser (output power 12 W) to increase the axial brightness by a factor of 17.