Comb-Integrated Photonic Hardware for Energy-Efficient Routing (CIPHER)

Modern computational workloads, dominated by the rapid rise of artificial intelligence (AI) and large language models (LLMs), are currently pushing modern data center and high-performance computing (HPC) systems to their limit. With the end of Moore’s Law rapidly approaching, the dominant bottleneck in current systems is the interconnects between chips rather than the processing power of the individual XPUs. Photonic integrated circuits (PICs), particularly those based on silicon photonics (SiPh), hold exceptional promise for surpassing the current limits of these transceivers. These PICs can be directly co-packaged alongside XPUs and memory to minimize the lengths of copper traces, dramatically increasing bandwidth density and energy efficiency. Furthermore, PIC-based transceivers based on SiPh can be fabricated in standard 300 mm complementary metal-oxide-semiconductor (CMOS) foundries and exhibit exceptionally high yields comparable to those for electronic chips.  A significant advantage of optical communications is the ability to transmit multiple streams of data over a single fiber using dense wavelength-division multiplexing (DWDM). When combined with the potential for extreme device density of SiPh, DWDM provides an avenue for massively parallel scaling with hundreds or thousands of independent channels on each chip. However, a major gap in SiPh is the lack of an integrated DWDM light source capable of producing these wavelength channels (primarily due to silicon’s indirect bandgap). While integration of III-V materials into the SiPh fabrication process is a viable solution, these lasers are typically very large and have performance that degrades significantly at high temperatures. Notably, many CPO companies using DWDM are currently moving away from on-chip laser sources due to integration and temperature concerns, instead treating the optical source as an “optical power supply” located in a dedicated temperature-stabilized rack away from the harsh thermal environment of the XPU package. However, it remains a significant challenge to develop efficient, compact, and low-cost multi-wavelength sources that can be effectively utilized to power CPO systems.  To address these challenges, we propose a transformative system that relies on only a single monochromatic external laser source to generate tens to hundreds of distinct wavelength channels directly on a monolithic transceiver chip through a temperature-agnostic parametric nonlinear process. Our proposed solution will realize turnkey, energy-efficient multi-wavelength sources monolithically integrated into CPO transceiver PICs, addressing a critical gap in the current CPO landscape and enabling unprecedented interconnect bandwidth density and energy efficiency in future computing systems.