Iterative design of diffractive elements made of lossy materials

Diffractive surface relief elements made of lossy materials exhibit phase-dependent absorption, which not only reduces the efficiency but also distorts the signal if the surface profile is realized on the basis of a phase-only design. We introduce an extension of the iterative Fourier transform algorithm, which accounts for such phase-dependent absorption, and present examples of its application to the design of diffractive beam splitters. The operator required for taking absorption into account is chosen to maximize the efficiency of the found design.