All-dielectric high-efficiency reflection gratings made with multilayer thin-film coatings

We made a high-efficiency ref lection grating by coating a nine-layer quarter-wave system of ZnS/Na(3)AlF(6) directly onto a surface-relief grating in photoresist. Eff iciencies of 70% and 84% were measured at the firstorder 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 eff iciency is to improve the contour conformation of the coated dielectric layers.