Design of free-space optical interconnection systems utilizing diffractive optics

Abstract

Free-space optical interconnects can be used to provide communication between sources and detectors (in the same or different planes) in a digital optical processor. Diffractive optics are particularly well suited to perform this interconnection because of their high efficiency, computerized design, and microelectronics fabrication compatibility. Free-space optical interconnection systems can be classified by their degree of space-variance. Space-invariant systems make use of one point spread function for all sources. Space-variant systems, on the other hand, use one point spread function per source. In between these two extremes, there are systems that divide the sources between several point spread functions. Which one of these systems will be best suited depends on the given interconnection pattern, e.g., perfect shuffle, hypercube, or twin butterfly. The design of all of these systems is studied from a practical fabrication standpoint. System volume is calculated in terms of parameters such as the f/No. of the diffractive lens, the wavelength of light, and the total number, size, and separation of the optical sources and detectors. Performance issues such as interconnection complexity, diffraction efficiency, aberrations, and signal to noise ratio are discussed. Tradeoffs between parameters such as volume, hologram complexity, and performance are determined and discussed.