Fabrication and Passive Assembly of Broadband Evanescent Couplers for Sustainable Pbps Co-Packaged Optics

A passively assembled chip-to-package substrate evanescent coupler between silicon nitride and silicon was experimentally demonstrated across the 1480-1640 nm wavelength regime with a 0.39 ± 1.06 dB coupling loss at 1550 nm, a 160 nm 1-dB wavelength tolerance (1480-1640 nm), and a 1-dB lateral alignment tolerance of ± 1.56 𝜇𝜇m. The thermal stability was evaluated from 23-60°C with average coupling loss and alignment tolerance varying by less than ± 0.35 dB and ± 30 nm, respectively. The repeatability of the packaging process flow was also evaluated by measuring coupler performance across four separately packaged systems, with a total range of 1.5 dB for coupling loss observed. Results show the viability of this coupler to help achieve Pbps co-packaged optics switch performance by eliminating active fiber-to-chip alignment and scaling down optical input/output pitch at the die level.