Abstract

To exploit the full potential of parallelism of light in optical processing systems it is of paramount importance to have optical components which can efficiently generate arrays of >100 × 100 beams and/or images. In this paper we report on fabrication of very large binary phase grating beam splitters, better known as Dammann gratings. These space-invariant fan-out elements are the essential components when solving alloptical digital logic based 2-D and 3-D problems. Using very advanced computational techniques such as simulated annealing and downhill greedy algorithm, we have been successful in calculating the structure of fan-out elements as large as 200 × 200. The calculated structures have been plotted using electron-beam lithographic techniques with resolution of 0.1 μm. These computer-generated amplitude holograms, to our knowledge, are the largest fan-out elements fabricated to date. These amplitude masks have been copied in a range of materials including thin films of metals, dielectrics, photoresists, and bleached silver halide holographic plates to create phase elements. This results in an increase in the 2-D diffraction efficiency of the elements from 15% to >65%.

© 1989 Optical Society of America