Theory and Applications of Free-Space Digital Optical Computing

A methodology for designing digital circuits is described for systems using free-space optics as an interconnection medium. Free-space optics offers the potential for a connectivity advantage over guided-wave optical interconnects and electronic interconnects, but new design techniques are needed to exploit that potential. Connections are made among arrays of optically nonlinear logic gates with regular interconnection patterns such as perfect shuffles, banyans, and crossovers. Design methods are based on symbolic substitution which is a form of cellular automata suited for array scale operations. Methods are introduced in the form of simple automata that are relatively easy to implement with free-space optics. More complex techniques are presented that utilize regular interconnects among logic gates and yield digital circuits nearly as efficient as conventional design techniques would allow utilizing arbitrary interconnects, but that are suited for a simpler free-space architecture.