Low-Loss Chip-to-Chip Optical Interconnection Using Multichip Optoelectronic Package With 40-Gb/s Optical I/O for Computer Applications

Abstract

We have developed novel optoelectronic packages and optical transmission system using an optical connector with an external optical waveguide to achieve low-loss chip-to-chip optical interconnections for computer systems. In order to connect the package and the connector, we have also proposed a socket as a coupling structure to realize an all passive alignment and high coupling efficiency. We have demonstrated high-speed and error-free signal transmission with four channels at 10-Gb/s/ch and up to 12-Gb/s/ch. Optical input and output (I/O) interfaces, including optical devices and controller integrated circuits (ICs), have been constructed onto the package surface by conventional flip-chip mounting. The optoelectronic package has optical waveguide holes (OWGHs) to pass optical signal vertically from a vertical-cavity surface-emitting laser (VCSEL) and to a photodiode (PD). The OWGHs consist of core and cladding material to enhance optical confinement. The optical connector that is just set underneath the package with two guide pins contains the thin-film polymer waveguide with 45 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> -ended mirrors to bend the optical signal. Therefore, the shorter optical coupling distance has achieved low-loss optical link without microlenses between packages. We have also proposed an alignment structure to easily enable passive alignment, which is based on existing land grid array (LGA) packages and sockets clamping structures to simultaneously improve cost-competitiveness and usability.