Demonstration of Silicon-Photonics Hybrid Glass-Epoxy Substrate for Co-Packaged Optics

To realize a new package substrate for co-packaged optics, a silicon-photonics hybrid glass-epoxy substrate was demonstrated. In the substrate, silicon photonics dies working as optical/electrical conversion engines are embedded. Additionally, it includes optical redistribution composed of polymer waveguides and mirror-based optical coupling structures between the polymer and silicon waveguides. A demonstration sample was designed for a total bandwidth of 10 Tbps using silicon photonics dies with arrayed waveguide gratings, wavelength splitters, and polarization splitters/rotators for 16-ch wavelength division multiplexing (WDM). It was fabricated using unique key technologies, such as silicon photonics embedding, micromirror fabrication, and single-mode polymer waveguide fabrication. Its wavelength multiplexing operation and signal transmission characteristics were evaluated. As a result, the hybrid substrate was discovered to be capable of 112 Gbps pulse amplitude modulation 4 (PAM-4) transmission with a 16-ch WDM function because the transmitter dispersion and eye closure quaternary (TDECQ) values of less than 3.4 dB were obtained and 16-ch WDM spectrum were clearly visible. To the best of our knowledge, the working of such a hybrid substrate was demonstrated for the first time. This demonstration implies that the hybrid substrate is feasible, and the above-mentioned novel technologies are crucial to its development.