ENABLING TECHNOLOGY FOR FABRICATION OF METER-SCALE GRATINGS FOR HIGH-ENERGY PETAWATT LASERS

摘要

We report on the construction, commissioning and characterization of a reactive ion mill capable of submicron pattern transfer into hard dielectric materials on optical substrates as large as 2 x 1 m, for application to fielding High-Energy Petawatt (HEPW) capability on the National Ignition Facility (NIF) laser. Scanning Faraday cup current probe measurements have been used to optimize the ion beam spatial uniformity. Using process parameters obtained from this study, an 81 cm round optic was etched, and etch depth uniformity of +/- 3.1% absolute was demonstrated Uniformity of multilayer dielectric gratings of designs employing an etch-stop layer will have etch depth uniformities of approximately a factor of 10 better than this. We also report on initial results of etching multilayer dielectric gratings.