Polymer-Based Packaging-Compatible Board-Level Optical Bus

In this proposed Phase II program we will develop board-level optical waveguides to alleviate the ever-tightening electrical interconnection bottleneck. VLSI provides fast intrinsic signal speeds but these speeds cannot be supported by electricalinterconnects between other chips on the same board. Conversion to optical interconnects at the intra-board level can overcome these limits. The practical limits of optical interconnects arises from the optoelectronic transmitters and receivers, whichcurrently have bandwidths up to 10GHZ. The emerging 40-GHz OC-768 telecommunications standard is a strong indication that optical interconnects will keep pace with VLSI for many years. However, their cost-effective assimilation into conventionaltechnologies remains the major unresolved issue. Therefore, we propose an optoelectronic board-level bus employing a fully imbedded optical interconnection layer based on polymeric waveguides, thin-film vertical-cavity-surface-emitting lasers (VCSELs) andthin-film metal-semiconductor-metal (MSM) photodetectors, integrated onto a PCB structure and planarized to allow conventional integration of noncritical electrical interconnects. Optical couplers will couple light between the transceivers and the chipsmounted on the boards's surface. By demonstrating these integrations we will prove the practicality of high speed board-level optical interconnects, which should lead to Phase III commercialization. The proposed technology to be developed replacesboard-level electrical interconnects with optical interconnects for critical high-speed signals. Because the optical interconnectivity layer is embedded in an otherwise conventional printed circuit board (PCB), this technology supports conventional PCBdesign and fabrication practices. Electronics engineers can design systems utilizing both electrical and high-speed optical interconnects without concerning themselves with the unfamiliar optical technologies. This should result in broad marketacceptance. Once accepted the technology should continue to be useful for many years as advancements in telecommunications optoelectronic devices are readily incorporated into the board level optical interconnects.