2026-09-24T01:33:32Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/130152 2026-02-10 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-08-01 The student, Haonan Wu, accepted the attached license on 2025-07-14 at 17:40. The student, Haonan Wu, submitted this Dissertation for approval on 2025-07-14 at 20:13. This Dissertation was approved for publication on 2025-07-18 at 13:24. DSpace SAF Submission Ingestion Package generated from Vireo submission #22446 on 2025-10-25 at 15:53:18 High-speed oxide-VCSELs for cryogenic computing applications Wu, Haonan 2025-07-18 Feng, Milton Feng, Milton Dallesasse, John Jin, Jianming Dragic, Peter Cryogenic Photonic Interconnect Vertical-cavity-surface-emitting-laser (vcsel) Cryogenic Physics Opto-electronic Packaging Artificial Intelligence eng The rapid growth of artificial-intelligence workloads and the emergence of superconducting and quantum processors are pushing data-movement requirements far beyond what conventional electrical links can sustain—especially inside cryogenic environments, where thermal budgets are exceptionally tight. This dissertation advances vertical-cavity-surface-emitting-laser (VCSEL) technology from its traditional role in room-temperature data centers to a new generation of energy-efficient optical transmitters capable of operating at temperatures down to 2.6 K. After reviewing VCSEL lasing physics and oxide-aperture design trade-offs, the work introduces a custom epitaxial platform and fabrication flow that enable reliable cryogenic operation. A fully packaged 4 K optical link directly driven by a superconducting single-flux-quantum circuit is demonstrated, followed by a record-setting 128 Gb/s PAM-4 link at 2.8 K—the fastest cryogenic optical transmission reported to date. To further reduce heat dissipation, a sub-micron-aperture architecture is developed. Shrinking the oxide aperture to 0.9 µm yields an unprecedented threshold current of 50 µA at 3 K and an energy cost of only 45.5 fJ bit⁻¹ while sustaining 112 Gb/s modulation, establishing a new benchmark for cryogenic optical interconnects. Because even microwatt-scale self-heating can degrade performance at deep-cryogenic temperatures, this dissertation also presents a novel experiment–simulation co-design framework that combines Cryo-VCSEL wavelength-shift thermometry with nonlinear three-dimensional finite-element Cryo-VCSEL thermal modeling. The model captures temperature-dependent thermal behavior of the Cryo-VCSELs from 2.6 K to 130 K, accurately predicting cavity temperatures and guiding design rules to mitigate thermal rollover. Collectively, these results show that oxide-confined VCSELs can deliver terabit-per-second-class bandwidth with femtojoule-level energy efficiency at cryogenic temperatures, paving the way for scalable optical I/O in superconducting and quantum computing systems. The thesis concludes with a roadmap for high-power single-mode cryogenic VCSELs, large-scale VCSEL arrays, and integrated electro-optic–thermal design tools that will further unlock the potential of cryogenic photonic interconnects. 2025-08 Text https://hdl.handle.net/2142/130152 Copyright 2025 Haonan Wu Electrical & Computer Eng Electrical & Computer Engr University of Illinois Urbana-Champaign Ph.D. Dissertation