Planar optics as the technological platform for optical interconnects

Abstract

interconnects without major consequences for the computer architecture or the svsteni assembly. This situation changesdraniaticallv if the potential of free—space optical interconnects is to be exploited for short distance comniunicatioii. Theinherent parallelism of free-space optics. being the most important advantage. requires fundamental changes of the systemarchitecture and assembly. The generally accepted conceptual approach for this situation is based on so-called smart pixelarrays (SPAS). SPAs arc 2D arrays of optical input and output devices integrated with electronic logic circuitry. SPAsprovide the device planes which can be interconnected to fully functional data routing or processing svstenis using free-space optics II.Directl evolving froni electronic semiconductor technology the fabrication of smart pixel arrays eniplovs lithographicintegration techniques. This has been very different for optical interconnection systems. Most of the prototypes using free-space optical interconnects built so far are still using optoinechanically aligned systems. With planar free—space optics.however. a concept for the integration of such optical systems has been successfully demonstrated. The major advantage ofplanar optics lies in the fact that it eniploys standard lithographic techniques to build fiilly integrated optical systemswhich arc extremely compact and robust. Thus the integrated free-space optical system as well as the optoelectronics canbe fabricated with the sanic technological approach. Generally. however. different substrates are necessary for electronicsand optics so that monolithic integration is not feasible. One of the topics to be addressed is the definition of suitableinterfaces between planar free-space optics. fiber optics. and optoelectronics.