Theses Doctoral

Robust and Scalable Silicon Photonic Interconnects and Devices

Novick, Asher

At the same time as Moore’s law is reaching it’s limits, there has been exponential growth in required computation power, most notably driven by the widespread deployment of artificial intelligence (AI) and deep learning (DL) models, such as ChatGPT. The unprecedented modern, and projected, bandwidth density requirements between compute needs for high performance (HPC) and data center (DC) applications leads directly to an equally unprecedented need to supply and dissipate extreme amounts of power in ever smaller volumetric units. While at smaller scales this becomes a question of power dissipation limits for discrete components, in aggregate the power consumed across the full system quickly adds up to becoming an environmentally significant energy drain.

Traditional electronic interconnects have failed to keep pace, both in terms of supporting bandwidth density and achieving sufficient energy per-bit efficiency, leading to optical interconnects becoming the dominant form of high-bandwidth communication between nodes at shorter and shorter reaches. Co-packaged silicon photonics (SiPh)s have been proposed as a promising solution for driving these optical interconnects. In fact, SiPh engines have already become widely accepted in the commercial ecosystem, specifically for network switches and plugable optical modules for mid- (10 m - 500 m) and long-haul (≥2 km) applications.

The work in this thesis proposes novel integrated SiPh interconnect architectures, as well asnovel devices that enable them, in order to push SiPh driven interconnects down into the inter-chip scale, inside the compute and memory nodes (< cm), as well as all the way out to the low-earth orbit (LEO) inter-satellite scale (> 1000 km). In the case of the former, recent advances in chip-scale Kerr frequency comb sources have allowed for fully integrated ultra-broadband dense wavelength division multiplexing (DWDM). To take full advantage of these integrated DWDM sources, similar advances must be made at both the architecture and device levels. In the latter case, interest in inter-constellation connectivity is growing as LEO becomes saturated with varying satellites owned by private and public entities. For these constellations to communicate directly, a new class of satellite must join the sky, with adaptive communication capabilities to translate Baud rate and modulation format between otherwise incompatible constellations. To support each of these applications with integrated photonics solution, advances in both SiPh architectures and the devices that comprise them.

This work first presents an overview of the system-level challenges associated with such links, including novel proposed integrated interconnect architectures, and then explores novel photonic devices that are designed to enable critical functionality and overcome system-level limitations. The advances demonstrated in this thesis provide a clear direction towards realizing a future fully permeated by ultra-efficient optical connectivity, supporting resource disaggregation and all-to-all connectivity from green hyper-scale data centers all the way to LEO.

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More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Bergman, Keren
Degree
Ph.D., Columbia University
Published Here
June 28, 2023