High-efficiency dielectric reflection gratings: design, fabrication, and analysis

We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplificat ion, high-power lasers. The design of the system combines a dielectric mirr or and a well-defined corrugated top layer to obtain optimum results. The r ules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littr ow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer s tack with electron-beam lithography. The multilayer system was fabricated b y conventional sputtering techniques onto a flat fused-silica substrate. Th e parameters of the device were measured and controlled by light scatterome ter equipment. We measured 97% diffraction efficiency in the -1 order and d amage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, r espectively, at a wavelength of 532 nm in working conditions. (C) 1999 Opti cal Society of America.