Optoelectronic parallel processing with surface-emitting lasers and free-space interconnects

Parallel optoelectronic processing that uses smart pixel arrays and free space interconnections may provide an attractive alternative to applications that exhibit a large degree of functional parallelism and require massive input/output data rates. Two fine-grain parallel architectures based on two-dimensional arrays of processing elements are discussed in this paper. The logic complexity of the smart pixels ranges from two-input AND and XOR gates for a database filter to multiple-input multiple-output compare-and-exchange modules for a recirculating bitonic sorting unit. Both systems use vertical-cavity surface-emitting lasers as light sources but light detection and logic are implemented differently. The data filter uses GaAs-based phototransistors while the sorting unit requires silicon detectors and CMOS circuitry for its more complex logic. The free-space one-to-one interconnection patterns required between processing planes can be realized with either refractive or diffractive optics and their simplicity and regularity permit easy scale-up