We made a high-efficiency reflection grating by coating a nine-layer quarter-wave system of ZnS/Na3AlF6 directly onto a surface-relief grating in photoresist. Efficiencies of 70% and 84% were measured at the first-order Littrow mount with the laser beam incident from the air side and from the substrate side, respectively. The experimental results are in qualitative agreement with theoretical predictions. The key to further improvement in the diffraction efficiency is to improve the contour conformation of the coated dielectric layers.
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