Interference effects in far-field diffractive optical elements

The effects of interference between closely packed diffraction orders in th e far held are studied for a number of different scalar-domain diffractive optical elements (DOE's). We demonstrate that there are specific order sepa rations that minimize the observed degradation in the far-field output unif ormity. Finally, a DOE that is designed to ensure that the order separation lies near one of these minima is compared with a more general design that produces an equivalent far-field output. (C) 1999 Optical Society of Americ a.