Soft-lithography-based Inter-chip Optical Interconnects

Abstract

The increasing performance of microprocessors leads to higher bandwidth require- ments for the data ∞ow to and from the processor. Today, all signaling on a PCB is performed electrically, using copper lines that are integrated in the board. However, issues such as prop- agation loss and inter-channel crosstalk limit the scalability of electrical interconnects to ever higher bandwidth densities. Optical interconnects feature a higher bandwidth £ length prod- uct, are more power-e-cient and enable a higher bandwidth density than electrical interconnects do. This paper describes a kind of two-dimensional monolayer optical interconnects providing interconnections between chips on conventional PCB. We have designed a soft-lithography-based, versatile coupling structure with a 45 - total internal re∞ector (TIR), a beam duct, and a polymer waveguide in order to vertically couple light beams between transmitter (or receiver) and the waveguide layer. This proposed integrated architecture of a polymeric optical interconnection has been demonstrated to be advantageous in the aspects of misalignment tolerance, ease and low cost of fabrication, as well as relative simplicity in deployment. We also investigated the characteristics of in-plane connections including cross-over and branching nodes in the optical interconnects with experimental and theoretical analysis. The theoretical crosstalk, as calculated by a function of crossing angle, was determined for a set of interconnect pairs with varying cross- sections, and was compared with experimental measurements. Furthermore, a suitable branching angle was found for branching node and the efiects of short-distance mode scrambling in highly multimode polymer waveguides were studied in detail in this paper too.