The efficiency of phase gratings used for array illuminators can be improved by increasing
the number of phase levels in computer-generated diffraction gratings. This is of interest to
provide power to two-dimensional arrays of optical logic devices that are used for optical
computing purposes. The theory and fabrication techniques are described, and the
experimental performance of a four-level grating that produces a 5× 5 array is presented.

Computer-generated gratings which produce a number of equal intensity diffraction orders
have been of interest recently for various applications. One application is the distribution of
light energy on 2-D arrays of optical logic devices in an optical computer. Different schemes
to achieve high uniformity and high efficiency have been investigated. Our approach is an
extension of Dammann's theory of binary diffraction gratings. 1 An increase in afficiency can
be obtained by using more than two phase levels. Gratings were fabricated using quartz …