Heterogeneous Integration in Co-Packaged Optics

Generative artificial intelligence (GAI) and Large Language Model (LLM) require data center to have higher bandwidth, and better energy efficiency. To achieve this, Co-packaged optics (CPO) is one of the future directions that leverages advanced packaging with integrated photonics. However, this tight integration complicates data center system design and multi-physics interactions, including electrical, optical, thermal, mechanical, and material aspects. In this paper, heterogeneous integration (HI) in CPO is discussed. Multi-physics packaging is exemplified with two cases. Challenges in HI technologies are reviewed and corresponding mitigation methods are provided, including 1) thermal crosstalk within the electrical domain and between the electrical and the optical interaction, 2) SIPI of wide-and-slow and narrow-and-fast channel links, and 3) pros and cons of interposer material. Integrated photonics part is introduced and is composed of 1) light sources, 2) optical coupling strategies, 3) fiber attach schemes with advanced packaging, and 4) integrated optical technologies, e.g. novel microlens, optical TSV, 3D waveguide, and optical 3DIC. This article aims to identify the key HI challenges in CPO and points out the potential solutions for future CPO system advancement.