Robust photopolymers for MCM, board, and backplane optical interconnects

A robust polymeric waveguide technology is proposed for affordable optoelectronic interconnects in massively parallel processing applications. We have developed high-performance organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry. These materials are formed from highly-crosslinked acrylate monomers with specific linkages that determine properties such as flexibility, toughness, loss, and stability against yellowing. These monomers are intermiscible, providing for precise adjustment of the refractive index from 1.30 to 1.60. Waveguides are formed lithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser direct-writing. A wide range of rigid and flexible substrates can be used, including glass, quartz, oxidized silicon, glass-filled epoxy printed circuit board substrate, and flexible polyimide film. Our waveguides are low loss (0.02 dB/cm at 840 nm) as well as temperature resistant (over 65 years at 100 degrees C) and humidity resistant (no effect on unpackaged guides after 600 hours at 85 degrees C 85% RH), enabling use in a variety of demanding applications. We discuss the use of these materials on multi-chip modules (MCM's), boards, and backplanes. Waveguiding structures measuring tens of inches in length can be produced on backplanes, and guides that are meters long can be laser-written on rolls of plastic. We also discuss the fabrication of symmetrically-clad flexible strips of waveguide arrays that are compatible with MT-type connectors.