Increasing the functionality of free-space micro-optical intrachip modules with DOEs: towards reconfigurable photonic interconnects

Abstract

Over the past few years state-of-the-art point-to-point optical interconnects have shown the potential to fulfill the ever increasing demand for higher data communication bandwidth. Still, for very short distances, electronic interconnects are favoured over optical interconnects because electronics is a much more mature and established technology. However, it is predicted by the international roadmap for semiconductor technology that electronic interconnects will encounter their limitations in the very near future [1] . To help alleviating the electrical interconnect bottlenecks over this range of distances, photonic interconnect technologies are continuously improved. However, to replace electronic interconnect technologies for inter-and intra-chip distances with optical links, the photonic contenders should not only outperform their electronic counterparts in bandwidth, power consumption and latency specifications. Photonic interconnects should also allow more complex and richer interconnect patterns, and add functionality beyond the typical standard point-to-point interconnects, by e.g. allowing for one-to-many interconnects (signal broadcasting) and reconfigurable point-to-point interconnects. In this paper we study, based on the Rayleigh-Sommerfeld propagation method, the potentialities of three dimensional micro-optical pathway blocks combining refractive microlens arrays, reflective micro-prisms and diffractive fan-out elements, to enhance the functionalities of short-distance intra-chip optical interconnects. As an example, we demonstrate the possibility to enhance the functionality of point-to-point interconnection to that of broadcasting data over a chip. We then illustrate this example by a quantitatively elaborated design of a fan-out element from a VCSEL array to a detector array with a 1 to 9 signal broadcasting for every source. Furthermore we show that with the use of DOE's we can achieve a broadcasting functionality that can lead towards reconfigurable optical interconnects, with the aid of wavelength sensitive resonant cavity detectors and WDM-inspired interconnection schemes.