Research on Integration of Photonic and Electronic Chips Based on Glass Interposer (Invited)

In recent years, with the widespread adoption of new technologies such as the IoT, 5G and AI, data centers have faced increasing demands to process and transmit large volumes of data. Co-packaged optics (CPO) technology integrates photonic integrated circuits (PICs) and electronic integrated circuits (EICs) on the same interposer, achieving short-distance interconnect, low power consumption, low latency and high integration density. Glass is chosen as the interposer material due to its excellent dielectric and optical properties. This study investigates the integration of photonic and electronic chips based on glass interposer. A structure of glass interposer with high-performance computing (HPC) chips was proposed, and the problem of preparing a redistribution layer (RDL) with small linewidths and spacings on a large-area interposer was solved by splitting the design layout of RDL. Additionally, the electrical loss of two different dielectric layers, polyimide (PI) and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}$</tex>, was explored. This study optimized the method for fabricating optical waveguides on glass surfaces. Optical waveguides with a horizontal mode field diameter of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10 \mu \mathrm{m}$</tex> and a vertical mode field diameter of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$9 \mu \mathrm{m}$</tex> at 1550 nm were prepared by ion-exchange (IOX) and annealing processes. Multistep grinding and polishing were designed to reduce the coupling loss at waveguide end faces. The transmission loss at the C-band of optical communication was measured at 0.8 dB/cm and the coupling loss was 0.3 dB/facet. An evanescent coupler based on tapered waveguides and a silicon nitride loading strip waveguide was proposed for optical coupling between glass and PIC waveguides. Finally, a possible packaging form for 3D high-density integration of photonic and electronic chips based on glass interposer was briefly introduced.