Optical and mechanical issues in free-space digital optical logic systems

Abstract

Three-dimensional array logic was recently demonstrated by optically interconnecting two-dimensional arrays of symmetric self-electro-optic effect devices (S-SEEDs).1 As in the operation of electronic logic, logiclevel uniformity of the optical input signals to each optical logic gate is necessary. As the outputs of one optical-logic-device array propagate to the next array, spatial variations of the logic levels can be introduced. Logic-level nonuniformity can accumulate from optical sources (spot-array generation, geometric aberration, and polarization effects), mechanical sources (misalignment and lack of stability), image plane sources (dust, damage, and device nonuniformity), and laser sources (wavelength and mode variations). We have found that although individual nonuniformity contributions can be kept to less than 10%, in complex systems the total accumulation of nonuniformity errors can exceed ±40%. These large variations of the input logic levels introduce errors in the desired logical decisions. The system constraints and limitations brought about by these nonuniformity contributions will be discussed, and experimental results will be presented.