<title>High-efficiency computer-generated holograms</title>

Abstract

Various diffractive optical elements have been fabricated for the visible wavelength region, mainly for laser beam splitting purposes, but also for the generation of arbitrary but predetermined intensity patterns (e.g. spirals, logos etc.). To obtain high efficiencies the computer-generated holograms were realized as transmissive diffractive phase elements (DPE). More detailed we report on a beam splitter which was intended to distribute an incoming laser beam into 40 partial beams of equal intensities arranged equidistantly on a circle. These circular beam splitters--designated to be used in a measuring system--were realized as binary phase elements. In addition DPEs, that generate a given arbitrary intensity pattern, were produced in 2- and 8-level approximation. The computer-generated phase elements with feature sizes down to the sub-micrometer range were fabricated in quartz-glass by means of microstructuring techniques. Due to our precise and well developed processes we realized binary- and multilevel microstructures of high optical quality. For the binary 1:40 beam splitters we reached diffraction efficiencies of about 60% and uniform spot intensities of better than +/- 2.5% of the average intensity value. The measured efficiency of the eight-level pattern generators was higher than 80%. The optical characterization of our components showed a good agreement with the results expected from simulations. Using simple embossing techniques we were able to replicate first test samples in organic polymers which showed good optical performances.