Abstract

Space-invariant holographic fan-out elements are important in most parallel optical processing and computing networks: These components can, for example, deliver biasing power for an array of optically bistable logic gates and can supply an array of point sources in the input plane of any space-variant interconnect. The primary figures of merit characterizing the performance of any optical-array generator are the diffraction efficiency and the array uniformity (reconstruction error). When the number of beams in the array is large, the size of the smallest feature becomes an important fabrication consideration. Using these figures of merit, we compare the performance of different binary-phase (Dammann grating) and multiple-phase kinoform Fourier-domain holograms generating large beam arrays. The fabrication tolerances of Dammann gratings and kinoforms are evaluated by a statistical approach, and a technique for maximizing the minimum feature size in the structure of Dammann gratings is discussed. The latter is important not only as a fabrication consideration but also because Fourier optics can be expected to fail if features smaller than about 5λ are present. Experimental results are presented on the largest space-invariant array generators reported so far: a conventional 201 × 201 beam Dammann grating, a modified 128 × 128 Dammann grating, and a 32 × 32 kinoform.

© 1990 Optical Society of America