Glass Platform for Co-Packaged Optics

Placing the electrical and photonic chiplets in a single package leads to significant power reduction. Chiplets are connected by fine-line electrical routing over a length of a few millimeters and optical interconnects in the package connect photonic chips with optical fibers for off-package communication. A packaging substrate made of glass with optical waveguides, through glass vias and electrical redistribution layers inside a single-sided cavity enables lower-cost assembly. A single-sided 50 μm deep cavity was etched in glass, and electrical copper lines with 5 μm in height and width were deposited on the floor of the cavity. Ion-exchange (IOX) waveguides with propagation loss of <0.1 dB/cm were fabricated below the glass surface. For flip-chip assembly of photonic chips and optical coupling with the IOX waveguides at the top surface of the glass, all electrical interconnects were located inside the cavity. Photonic chips with silicon nitride waveguides were optically coupled to glass waveguides with a minimum loss of 0.5 dB, achieved by fiducial-aligned flip-chip photonic assembly. A low-profile fiber connector with height of 4.4 mm connects the integrated ion-exchanged waveguides with the optical fibers. Average connector loss of 0.83 dB was demonstrated with physical contact between fibers and IOX glass waveguides.