Opto-ViT: Architecting a Near-Sensor Region of Interest-Aware Vision Transformer Accelerator with Silicon Photonics

Vision Transformers (ViTs) have emerged as a powerful architecture for computer vision tasks due to their ability to model long-range dependencies and global contextual relationships. However, their substantial compute and memory demands hinder efficient deployment in scenarios with strict energy and bandwidth limitations. In this work, we propose Opto-ViT, the first near-sensor, region-aware ViT accelerator leveraging silicon photonics (SiPh) for real-time and energy-efficient vision processing. Opto-ViT features a hybrid electronic-photonic architecture, where the optical core handles compute-intensive matrix multiplications using Vertical-Cavity Surface-Emitting Lasers (VCSELs) and Microring Resonators (MRs), while nonlinear functions and normalization are executed electronically. To reduce redundant computation and patch processing, we introduce a lightweight Mask Generation Network (MGNet) that identifies regions of interest in the current frame and prunes irrelevant patches before ViT encoding. We further co-optimize the ViT backbone using quantization-aware training and matrix decomposition tailored for photonic constraints. Experiments across device fabrication, circuit and architecture co-design, to classification, detection, and video tasks demonstrate that Opto-ViT achieves 100.4 KFPS/W with up to 84% energy savings with less than 1.6% accuracy loss, while enabling scalable and efficient ViT deployment at the edge.