Investigation of polymer waveguides for fully embedded board-level optoelectronic interconnects
We proposed a fully embedded board-level optoelectronic interconnect structure utilizing polymer waveguides and 45-degree micro mirror light couplers. This structure is expected to provide high-speed, large bandwidth, low power dissipation, as well as compatibility to conventional PCB fabrication process, ease of optical alignment and packaging. High performance polymer waveguide with 45 degree micro mirror coupler is one key component to enable all these advantages. The performance analyses indicate that the polymer waveguide can provide low loss link for optical data and high channel density can be achieved without inducing significant crosstalk. Waveguide intersections and bends can be employed in the waveguide circuitry design to improve the design flexibility and interconnection density. 45 degree mirror couplers can provide high input and output surface-normal coupling efficiency. The fully embedded system features high tolerance to the linear and angular misalignments due to the possible fabrication imperfection. Ultradel 9000 series polyimides are used to form the waveguide and mirror couplers. Fabrication techniques are developed and discussed in detail. Waveguide array and mirror couplers with good quality have been fabricated and characterized. Preliminary integration of polymer waveguide array with MSM photodetector array through 45-degree micro mirror couplers is demonstrated and shows an aggregate bandwidth of 32GHz for a 1×12 channel array. Further integration is under development. An optoelectronic interconnect layer (OIL) will be developed and laminated with the other layers of PCB to improve system performance without inducing manufacturing difficulties.