Dielectric multilayer grating designs with maximum diffraction efficiencies

Diffraction efficiencies of binary dielectric multilayer gratings are calculated by combining thin film theory and scalar electromagnetic theory, and results are compared with efficiencies of conventional binary gratings, consisting of one single bulk material. By optimizing the number of layers and layer parameters such as material and layer thickness, multilayer grating designs are obtained showing diffraction efficiencies in the desired order close to the theoretical maximum and suppressing the zeroth diffraction order effectively. To meet technological requirements of etching process such as suitable etch-depth control, parameters of etch-stop layers are included into the calculation and optimization procedure. Manufacturing dielectric multilayer gratings including etch-stop layers will make it possible to obtain uniform etch profiles, a moderate surface roughness in the etched area, and high accuracies in etch depth without any online control devices.