Glass Substrate With Integrated Waveguides for Surface Mount Photonic Packaging

Co-packaged optics in next-generation datacenters require the assembly of multiple components on the same multichip module (MCM) and interconnection with hundreds of optical fibers. A novel photonic packaging substrate is required to leverage high-throughput electronic assembly with high precision optical alignment. This report highlights the results of glass substrate optimization to include optical waveguides, a fiber connector, and chip interfaces, as well as features for electrical connectivity, as a potential component for a co-packaging solution. Glass with smooth surfaces and high precision alignment features enables surface mounted flip-chip assembly of electrical integrated circuits, photonic components, and optical fiber connectors. All components will be placed by vision alignment using precise fiducials or passive alignment in mechanical features to the surface of the glass substrate with optical and electrical interconnects. Flip-chip assembly of photonic components is enabled by evanescent coupling with couplers having a minimum non-linear taper length of 1.5 mm. The designed interface loss to the integrated ion-exchanged glass waveguides is less than 1 dB with an interface which is robust to lateral misalignment of up to 4 microns. Light can be transmitted in the glass substrate with a propagation loss of 0.1 dB/cm. Fiber interfaces are mechanically and thermally decoupled from the photonic component and glass waveguides can fan-out the component pitch from 50 to 250 microns of the MTP-16 ferrule connector. The solder reflow compatible connector receptacle is passively aligned and demonstrate with an average loss of 0.68 dB.