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Yu, Shangxuan

University of British Columbia

Three-dimensional freeform optical waveguides, or photonic wired bonding (PWB), is a versatile technology that enables low-loss interconnects between photonics components. With two-photon lithography, PWB can match the mode profile and position mismatch between single-mode fibers, photonics integrated chips (PIC), and semiconductor lasers, rendering the costly active alignment obsolete. Despite the advantages of the PWB technology, compact packaging solutions must be developed to fully cultivate its potential in interconnecting photonics components and work with existing integrated photonics functionalities. We review the basics of photonics packaging. The working principle and technical specifications of PWB are summarized. Laser integration and fiber attachment methods are reviewed. More technical details like the fabrication process and structure of PWB are introduced. Moreover, we proposed a series of simulations to optimize the PWB geometry for efficient coupling. The mode coupler shape and its vertical offset tolerance are simulated by mode overlapping, and the constant cross-section waveguide's single operation condition and bending loss are investigated. The mode size convertor between mode couplers and constant cross-section waveguide is optimized to balance the footprint and good transmission. An intensity-modulated microring modulator (IM-MRR) based optical computing unit is demonstrated with PCB-based co-packaging with PWB for optical interconnection. A chip post-processing recipe is developed and calibrated for metalization rework. This is the first demonstration of using PWB for packaging neuromorphic systems. The potential of PWB to enable high-density optical I/O for the neuromorphic system is discussed. We propose a hybrid on-chip laser integration technology enabled by PWB. The photonics integrated chip (PIC) post-process and packaging process is illustrated. The deep reactive ion etching (DRIE) process is calibrated for etching on-chip recess cavities. Pure indium and Au₈₀S₂₀ preforms are tested for laser die soldering on bare silicon and gold-coated surface. A PWB-compatible compact assembly solution for electrical/optical co-packaging is developed. The assembly solution is implemented for investigating short-range optical feedback effects on distributed feedback lasers. The methods feature the least change on existing nanofabrication techniques while maintaining flexibility for off-the-shelf laser dies integration. This approach has great potential to enable low-cost hybrid integration for low-to-medium volume applications.

Text

2023-03-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84111

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/