Photonic Systolic Array for All-Optical Matrix–Matrix Multiplication

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Abstract:

Systolic arrays have proven to be highly efficient for parallelized matrix–matrix multiplication (MMM), utilizing synchronized, heartbeat-like data flows across an array of processing elements. While optical structures, such as waveguide crossbar arrays and Mach-Zehnder interferometer-based meshes, serve as photonic equivalents to the systolic arrays, the disparity between the two input matrices for multiplication—one using optical signals and the other with system-defined parameters—gives rise to a bottleneck in modern machine-learning tasks, such as evaluating attention scores in large language models. Here, a photonic systolic array that performs MMM entirely with optical signals is proposed, utilizing homodyne detection at each array cell. Adjoint-based design of compact on-chip freeform optical modules enables precise control of light flow without bulky waveguide coupling schemes. The operation of 4×4 and 2×2 photonic systolic arrays are numerically verified, achieving a theoretical computation density of 4.4 PMACs/mm2/s. This design marks a significant step toward practical photonic computing hardware for modern AI workloads.

Citation

J. Kim et al., “Photonic Systolic Array for All-Optical Matrix–Matrix Multiplication.” Laser & Photonics Reviews: e01995 (2025). https://doi.org/10.1002/lpor.202501995.

@article{kim2026_systolic,
    author = {Kim, Jungmin and Zhou, Qingyi and Yu, Zongfu},
    title = {Photonic Systolic Array for All-Optical Matrix–Matrix Multiplication},
    journal = {Laser \& Photonics Reviews},
    volume = {20},
    number = {7},
    pages = {e01995},
    keywords = {matrix-matrix multiplication, optical computing, systolic array},
    doi = {https://doi.org/10.1002/lpor.202501995},
    url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lpor.202501995},
    eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.202501995},
    year = {2026}
}

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