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Automated Curvy Waveguide Routing for Large-Scale Photonic Integrated Circuits

Hongjian Zhou, Keren Zhu, Jiaqi Gu

Abstract

As photonic integrated circuit (PIC) designs advance and grow in complexity, largely driven by innovations in photonic computing and interconnects, traditional manual physical design processes have become increasingly cumbersome. Available PIC layout automation tools are mostly schematic-driven, which has not alleviated the burden of manual waveguide planning and layout drawing for engineers. Previous research in automated PIC routing largely relies on off-the-shelf algorithms designed for electrical circuits, which only support high-level route planning to minimize waveguide crossings. It is not customized to handle unique photonics-specific routing constraints and metrics, such as curvy waveguides, bending, port alignment, and insertion loss. These approaches struggle with large-scale PICs and cannot produce real layout geometries without design-rule violations (DRVs). This highlights the pressing need for electronic-photonic design automation (EPDA) tools that can streamline the physical design of modern PICs. In this paper, for the first time, we propose an open-source automated PIC detailed routing tool, dubbed APR, to generate DRV-free PIC layout for large-scale real-world PICs. APR features a grid-based curvy-aware A* engine with adaptive crossing insertion, congestion-aware net ordering and objective, and crossing-waveguide optimization scheme, all tailored to the unique property of PIC. On large-scale real-world photonic computing cores and interconnects, APR generates a DRV-free layout with 14% lower insertion loss and 6.25x speedup than prior methods, paving the way for future advancements in the EPDA toolchain. Our codes are open-sourced at https://github.com/ScopeX-ASU/APR.

Automated Curvy Waveguide Routing for Large-Scale Photonic Integrated Circuits

Abstract

As photonic integrated circuit (PIC) designs advance and grow in complexity, largely driven by innovations in photonic computing and interconnects, traditional manual physical design processes have become increasingly cumbersome. Available PIC layout automation tools are mostly schematic-driven, which has not alleviated the burden of manual waveguide planning and layout drawing for engineers. Previous research in automated PIC routing largely relies on off-the-shelf algorithms designed for electrical circuits, which only support high-level route planning to minimize waveguide crossings. It is not customized to handle unique photonics-specific routing constraints and metrics, such as curvy waveguides, bending, port alignment, and insertion loss. These approaches struggle with large-scale PICs and cannot produce real layout geometries without design-rule violations (DRVs). This highlights the pressing need for electronic-photonic design automation (EPDA) tools that can streamline the physical design of modern PICs. In this paper, for the first time, we propose an open-source automated PIC detailed routing tool, dubbed APR, to generate DRV-free PIC layout for large-scale real-world PICs. APR features a grid-based curvy-aware A* engine with adaptive crossing insertion, congestion-aware net ordering and objective, and crossing-waveguide optimization scheme, all tailored to the unique property of PIC. On large-scale real-world photonic computing cores and interconnects, APR generates a DRV-free layout with 14% lower insertion loss and 6.25x speedup than prior methods, paving the way for future advancements in the EPDA toolchain. Our codes are open-sourced at https://github.com/ScopeX-ASU/APR.
Paper Structure (29 sections, 6 equations, 12 figures, 5 tables)

This paper contains 29 sections, 6 equations, 12 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Preliminaries
  3. VLSI Detailed Routing
  4. Photonic Design Rules
  5. Waveguide Spacing
  6. Bend Radius
  7. Waveguide Crossing
  8. Port Connection and Alignment
  9. Signal Integrity
  10. Schematic-Driven PIC Layout
  11. PIC Routing Quality Metrics
  12. Problem Formulation
  13. APR: Automated PIC Detailed Routing
  14. Accessibility-Enhanced Port Assignment
  15. Port-Group-based Net Order
  16. ...and 14 more sections

Figures (12)

  • Figure 1: Modern PIC scale and complexity require EPDA.
  • Figure 2: Compare properties/rules of EIC and PIC routing.
  • Figure 3: Algorithm flow of our APR framework.
  • Figure 4: (a) Port propagation and reserved port region help port access. (b) Port spreading removes congested ports in the same grid. (c) group-based net order with access point offset enables channel planning and allows potential crossing.
  • Figure 5: Parametric curvy-aware neighbors allow non-Manhattan curvy waveguide routing. Neighbors are automatically derived based on bending radius and grid size.
  • ...and 7 more figures