Communication in macrochips using silicon photonics for high-performance and low-energy computing

In this paper microchip technology was explored. In order to scale chip-to-chip I/O to the required communication performance and energy, optical interconnects between chips based on CMOS-compatible silicon photonics was proposed. One key component is an inter-chip optical coupler supporting wavelength-division multiplexing (WDM) functionality that enables face-to-face optical proximity communication (OPxC).The high-fidelity 10 Gb/s OPxC with reflecting mirrors micro-machined into silicon and co-integrated with low-loss SOI waveguides for packaged chip-to-chip communication was demonstrated. These devices were integrated through dry etching rib waveguides 8 mum wide that tapered to 13 mum wide and subsequently truncated with a wet-etched micro-mirror facet forming a 54deg angle with the (100) silicon surface. Light in waveguides on one chip can couple to waveguides on a second, facing chip upon face-to-face positioning so that the reflecting mirrors form a coupled pair and complete an OPxC hop. Inside a package, a chip-to-chip OPxC hop was measured to have optical coupling loss of 4dB; with precision aligned chips using a nano-positioning stage. When OPxC hops associated with the package are inserted into standard 10 Gbps links, it was shown that RMS jitter and amplitude metrics for data eye quality to be essentially unchanged (within 1%). This package-based self-alignment mechanism enables chip packages for many different classes of proximity communication. In this presentation, other critical components of chip-to-chip optical interconnects, including modulators and detectors, were also addressed.