Optimization of planar metallic nonrefracting transmission-grating profiles for mth-order intensity maximization in the soft-x-ray range

We derive the thickness profiles of metallic transmission-grating bars that maximize either the power throughput into the mth diffracted order or the ratio of the mth-order diffracted power to the total output power (in the soft-x-ray range). The derivation is performed for both general and symmetric bar shapes and for the two physically important cases of continuous gratings and gratings with integral bars. The analysis is valid for all cases in which the optical constants are general functions of position in a direction perpendicular both to the light and to the grating bars. Examples of some optimum profiles for gold in the soft-x-ray range are computed on the basis of the presented analysis and are tabulated for convenient reference.